Prepared August, 2000
Production Regions
Cotton is grown primarily in the eastern part of Arkansas known as the Mississippi delta. There is a relatively small amount of cotton grown in the southwest corner of the state. The highest number of cotton acres (approximately 42% of the harvested acres in 1998) is concentrated in the northeast counties of Arkansas. The counties in the southeastern region of the state account for approximately 31% of the harvested cotton.
Reduced tillage or no-till cotton provides growers an opportunity to limit tillage, reduce the potential for erosion and soil movement into surface water, and often will afford timelier planting. Two non-conventional systems that are most common in Arkansas are stale-seedbed and no-till.
Stale Seedbed Concepts
In the Fall:
Spring
Planting Time
No-Till Concepts
In the Fall
Spring
Planting Time
In Season
Conventional Tillage
The objective of preplant tillage is to provide a firm, weed-free, moist seedbed that is free of root zonecompaction. To reduce cost as much as possible, the number of trips across the field must be minimized.
The operations that should be accomplished include:
To reduce the number of trips, consideration must be given to the sequence of the required tillage operations:
To avoid reestablishing hardpans after deep tillage, limit preplant disking operations or use alternative field preparation tools such as field cultivators.
Several alternatives can be used to attain the desired end result; a suggested approach follows:
If at this point (1-2 weeks before planting) the beds are still well formed from the initial bedding operation and they are free of large vegetation, consider skipping the rebedding operation; simply knockdown and plant when the desired conditions for planting occur.
Planting
Planting should not start until soil temperature in the beds, knocked down to planting level, reflects a mid-morning temperature of 68o F at two inches deep for three consecutive days and there is a favorable five-day weather forecast. The two-inch soil temperature in the peak of a bed that has not been knocked down may be quite different from the soil temperature in the zone where the seed will actually be planted.
Attempting to define specific calendar dates for beginning, and for that matter ending, the planting period is somewhat hazardous because of wide year-to-year variability.
Generally, conditions favorable for planting do not occur before April 25; often it is later. Normally, the first week of May should be considered as the first period that is favorable for planting over most of the state. Growers in northeast Arkansas may find early May to be a more favorable period while those in south Arkansas may find late April more favorable many years.
The desired plant stand is 3 to 4 plants per row foot (41,267 to 55,023 plants per acre) for cotton planted at the conventional row spacing of 38 inches. Often the uniformity of plant distribution within the row and across the field can have as much or more impact on potential yield than will the number of plants per acre. The minimum stand recommendation is two plants per row foot or 27,110 plants per acre for 38-inch row cotton. On irrigated fields it may be possible to accept fairly uniform stands as low as 1.5 plants per row foot or 20,633 plants per acre, but some yield loss is probable.
Integrated Pest Management
The majority of Arkansas cotton is produced under an integrated pest management (IPM) program. The University of Arkansas Cooperative Extension Service personnel, private consultants, independent part time scouts, agricultural industry representatives and producers provide the monitoring or scouting.
Integrated Pest Management is a sustainable approach to managing pests by combining biological, cultural, physical and chemical tools in a way that minimizes economic, health and environmental risks. IPM centers on the organization of a systems type approach to the crop production plan. It is a management approach that relies, to the maximum extent possible and economically practical, on prevention or avoidance of the pest problems that are commonly encountered. Pest management practices include cultural control (includes transgenic cotton varieties), field monitoring/scouting, mechanical controls, and use of naturally occurring, or in some cases, applied biological control agents. When satisfactory non-chemical controls are not available or fail to provide adequate control, chemical controls are applied as needed based on established economic thresholds for the pest(s).
Several insects attack cotton at various stages of growth. The primary insect pests in Arkansas are the boll weevil (Anthonomous grandis grandis), bollworm (Helicoverpa zea), tobacco budworm (Heliothis virescens), thrips (Frankliniella spp.) and plant bugs (Lygus spp.). Secondary insect pests of cotton, which occur only occasionally, include the beet armyworm (Spodoptera exigua), fall armyworm (Spodoptera frugiperda), cutworm (various species), aphid (Aphis gossypii), stinkbug (Nezara viridula or Euschistus servus), and spider mite (Tetranychus urticae).
Insect populations vary depending on the area of the state where cotton is produced. The southern cotton producing areas tend to have greater insect problems than northern cotton growing areas. In the northern part of the state the slightly shorter growing season combined with much cooler winters, keep insect pest populations lower than the rest of the state.
BOLL WEEVIL
Of the primary insect pests of cotton, the boll weevil is one of the toughest to control. The boll weevil’s high reproductive capability and resistance to several insecticides allow this insect to build up to large populations quickly. The boll weevil is a greater problem in the southern part of the state where winter temperatures are warmer and overwintering habitats are more favorable. Forested areas around rivers, drainage ditches and bayous provide favorable overwintering sites in southern cotton growing areas. Cooler winter temperatures and less favorable overwintering habitats in the northern cotton growing areas cause higher mortality of overwintering boll weevil. Several counties in north Arkansas have very little woodland or other favorable overwintering sites that might favor survival of the boll weevil in the winter. Control for the boll weevil is similar throughout the state. When boll weevil populations reach economic damaging levels insecticides are the primary control measure. Insecticide application, especially those made during the early part of the growing season, often reduce beneficial arthropod populations and tend to increase occurrence of secondary pest outbreaks.
The damage done by the pest: Weevils puncture squares and bolls with their snouts to feed and to lay eggs. If a weevil puncture is topped with a whitish or brown bump or "wart", it is an indication that the female has laid an egg in the hole and sealed the puncture to protect the egg. This gluey substance is white on newly sealed egg punctures, but browns with age. Some weevil punctures will not have this sealer, particularly if the insect merely feeds. Normally, the weevil, which prefers squares, makes only one egg puncture per square, but it will select young bolls in many cases. One egg hole also is normal. Weevil damage will range from one or two locks per boll to complete boll loss since many punctured squares or young bolls will drop off after the pest drills the hole.
Life cycle: Total time from egg to adult ranges from 16 to 25 days; egg - two to three days; larva - five to eight days; pupa - three to five days; newly emerged adult ("callow" adult) - one day; feeding adult - five to eight days before egg laying. Adult females lay an average of 30 eggs each day for approximately 10 days. Each generation normally multiplies tenfold. The pests in a typical field can multiply about two and one-half times each week - about the same rate of increase as the squares in the field.
Boll weevils spend the winter in a semi-dormant state (reproductive diapause) in hardwood ground cover, such as patches of woods. During mild winters, they also can survive in grass or other cover. Usually four generations of weevils occur during the season. When daytime temperatures begin to rise above 70 degrees weevils begin emerging. Emergence may continue from before cotton is big enough to support the pests until July, peaking normally in May and June.
While there are not always clear-cut steps in the emergence of over-wintered weevils, the first adult in-field generation can begin emerging about a week after the first white bloom, with others following at about three-week intervals. Climate and weevil food supply can greatly influence peaks in weevil populations.
Critical timing of control measures: The applications of insecticides to control the boll weevil will normally be applied when square damage levels reach one damaged square per row foot. Treatment for suppression of overwintering boll weevils is determined using pheromone traps. If trap captures the week prior to squaring exceeds four weevils per trap per week, a suppression spray may be needed.
Yield losses attributed to pest: The average yield loss due to boll weevils was 2.08% from 1996-1998. Yield loss estimates do not include the costs associated with controlling or managing the pest.
Percentage of infested acres: The average percentage of boll weevil infested cotton acres was 83.5% from 1996-1998.
Chemical Control
Oxamyl
Trade names are Vydate L and Vydate C-LV. Approximately 60 percent of the cotton acres receive an application of oxamyl each year. Applications are made primarily by air. Applications rates average 0.24 pounds a.i. per acre. Approximately 3 to 4 applications are made each growing season. The preharvest interval for Vydate C-LV is 14 days. The preharvest interval for Vydate L is 21 days. The restricted-entry interval for both products is 48 hours.
Malathion
Trade name is Malathion ULV. Since the initial implementation of the Arkansas Boll Weevil Eradication Program in 1996 the use of malathion for boll weevil control has increased steadily. In 1999 15-20% of the cotton acres in Arkansas were treated with malathion for boll weevil control. In 2000 approximately 50% of the cotton acres were treated with malathion. Applications are made aerially or with mist blower ground equipment. The rate for aerial applications is 10 ounces of the undiluted ULV formulation. The rate for the mist blower ground application is 16 ounces of the undiluted ULV formulation. The preharvest interval is 0 days. The restricted-entry interval is 12 hours.
Methyl Parathion
Trade names are Methyl Parathion 4E and Penncap M. Approximately 35 percent of the cotton acres receive an application of methyl parathion each year to control boll weevils. Applications are made by ground and air with a larger percentage being applied aerially. Application rates average 0.42 pounds a.i. per acre. Approximately 1 to 3 applications are made each growing season. The preharvest interval is 7 days. The restricted-entry interval is 48 hours.
Cyhalothrin
Trade name is Karate. Approximately 30 percent of the cotton acres receive an application of cyhalothrin each year to control boll weevils. Applications are made by ground and air with a larger percentage being applied by air. Application rates average 0.03 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 21 days. The restricted-entry interval is 24 hours.
Cyfluthrin
Trade name is Baythroid 2. Approximately 30 percent of the cotton acres receive an application of cyfluthrin each year to control boll weevils. Applications are made by ground and air with a larger percentage being applied by air. Application rates average 0.04 pounds a.i. per acre. Approximately 2 to 3 applications are made each growing season. There is no preharvest interval. The restricted-entry interval is 12 hours.
Azinphosmethyl
Trade names are Guthion 2L, and Azinphosmethyl 2E. Approximately 1 percent of the cotton acres receive an application of azinphosmethyl each year to control boll weevils. Applications are made by ground and air with a slightly larger percentage being made by ground equipment. Application rates average 0.25 pounds a.i. per acre. Approximately 2 to 3 applications are made each growing season. There is no preharvest interval for mechanically picked cotton. The restricted-entry interval is 48 hours.
Esfenvalerate
Trade name is Asana XL. Approximately 4 percent of the cotton acres receive an application of esfenvalerate each year to control boll weevils. The type of application is evenly divided between ground and air. Application rates average 0.03 pounds a.i. per acre. Approximately 2 to 3 applications are made each growing season. The preharvest interval is 21 days. The restricted-entry interval is 12 hours.
Zeta-Cypermethrin
The trade name is Fury 1.5 EC. Approximately 5 percent of the cotton acres receive an application of zeta-cypermethrin each year to control boll weevils. Applications are made by ground and air with a larger percentage applied by air. Application rates average 0.04 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 14 days. The restricted-entry interval is 12 hours.
Control Alternatives
Pheromone traps and the Boll Weevil Eradication Program are the primary alternatives for controlling the boll weevil.
Originally started in North Carolina and Virginia in 1978, the Boll Weevil Eradication Program (BWEP) program has since been implemented by most of the other cotton producing states in the southeastern United States. The program began in Arkansas in 1996 in southwest Arkansas and expanded to southeast Arkansas in 1999. Central Arkansas began the program in 2000. The implementation of BWEP is expected over the rest of the state in the next eight years. The primary components of BWEP are timely applications of malathion and intensive use of boll weevil pheromone traps. It is a very intensive program that requires close monitoring of boll weevil populations in coordination with producers.
COTTON BOLLWORM and TOBACCO BUDWORM
The bollworm and tobacco budworm species comprise what is commonly referred to as the Heliothine complex. Both species belong to the Noctuidae family of insects and attack cotton in a similar fashion. In Arkansas, bollworm and tobacco budworm populations vary greatly from south to north. The overall population levels of the Heliothine complex are higher in south Arkansas. Both species occur as pests of cotton each year. Of the two species, the bollworm is a more frequent problem whereas the tobacco budworm is more difficult for producers to control. Tobacco budworms are resistance to many insecticides especially those in the pyrethroid class of insecticides. Over the past 10 years, the tobacco budworm has become a more difficult insect to control.
The damage done by the pests: The most obvious damage is feeding on squares and bolls, but bollworms and budworms can also reduce yields through secondary damage. Feeding damage often provides entry for disease organisms, which can lead to boll rot. This usually occurs in irrigated cotton, but it can occur in wet periods after rainfall.
Percentage of infested acres: The average percentage of bollworm and tobacco budworm infested cotton acres was 94.2% from 1996-1998.
Life cycle: Egg - three to five days; larva - 12 to 15 days spent feeding on cotton; pupa - 12 to 15 days, resting in top two to four inches of the soil; adult - moths emerge from pupae and begin laying eggs in 3 to 12 days. The development of one complete generation thus may require from 27 to 35 days. Female bollworm moths can lay from 250 to 1,500 eggs. In a normal season, there usually are about five generations, but some of these are spent on plants other than cotton. Normally, only two or three generations inflict important damage on cotton.
These worms overwinter in the soil, in the pupa stage, after going through a preparation phase. Moth migration is common and moths may move many miles. Expect the first generation in early spring. At that time, the pests develop on legume crops, such as crimson clover of alfalfa. The second generation apparently prefers corn, where bollworms are known as corn earworms. Third generation worms generally are the first infestation for cotton, but insects also will infest corn or grain sorghum if these crops are present. If corn or milo is close by, the third generation may leave and migrate into cotton. Also, roadside plants such as evening primrose attract bollworms.
Light intensity, rather than the time of day, triggers bollworm and budworm behavior. On an average day, light intensity of 800 footcandles, known to affect moth feeding, is reached at 4 to 5 p.m. Moths feed on nectar from flowers and the nectary glands of cotton. Aphid honeydew also is an attractive food, as well as water droplets. By 7 p.m., if the light intensity is around 28 footcandles, moths are triggered into laying eggs, which may continue until 9 to 10 p.m. Some eggs are laid in blooms so newly emerged larva may feed inside the bloom. Blossoms may fold over the pests, so insecticide coverage failure can occur. Newly hatched larvae may feed on leaves the first day before attacking squares and bolls.
Critical timing of control measures: Treat for 7000 (1 per 2 row feet) small larvae (< 0.25 inch) per acre. If larger larvae begin to develop in fields, treat for 3,500 (1 per 4 row feet) larvae. When damage to squares occurs, treat for 14,000 damaged squares (1 per row foot) plus eggs and small larvae. Insecticide applications should be timed to egg hatch.
Yield losses attributed to pest: The average yield loss due to bollworms and tobacco budworms was 3.47% from 1996-1998. Yield loss estimates do not include the costs associated with controlling or managing the pest.
Chemical Control - Ovicides
Sulprofos
Trade name is Bolstar 6. Approximately 2 percent of the cotton acres receive an ovicidal application of sulprofos each year. Applications are made primarily by air. The application rate averages 0.3 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 14 days. The restricted-entry interval is 24 hours.
Profenofos
Trade name is Curacron 8E. Approximately 17 percent of the cotton acres receive an ovicidal application of profenfos each year. Applications are made by ground and air with the majority being applied by air. The application rate averages 0.43 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 30 days. The restricted-entry interval is 48 hours.
Methomyl
Trade name is Lannate LV and Lannate SP. Approximately 6 percent of the cotton acres receive an ovicidal application of methomyl each year. Applications are made by ground and air with the majority being applied by air. The application rate averages 0.22 pounds a.i. per acre. Approximately 1 to 3 applications are made each growing season. The preharvest interval is 15 days. The restricted-entry interval is 72 hours.
Thiodicarb
Trade name is Larvin 3.2. Approximately 14 percent of the cotton acres receive an ovicidal application of thiodicarb each year. Applications are made by ground and air with the majority being applied by air. The application rate averages 0.18 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 28 days. The restricted-entry interval is 12 hours.
Acephate
Trade name is Orthene 90S and Orthene 75S. Approximately 4 percent of the cotton acres receive an ovicidal application of acephate each year. Applications are made primarily by air. The application rate averages 0.45 pounds a.i. per acre. Approximately 2 applications are made each growing season. The preharvest interval is 21 days. The restricted-entry interval is 24 hours.
Chemical Control - Larvae and Adults
Cyfluthrin
Trade name is Baythroid 2. Approximately 35 percent of the cotton acres receive an application of cyfluthrin each year to control larvae and adults of the bollworm and tobacco budworm. Applications are made by ground and air with a larger percentage being applied by air. Application rates average 0.03 pounds a.i. per acre. Approximately 2 to 3 applications are made each growing season. There is no preharvest interval. The restricted-entry interval is 12 hours.
Cyhalothrin
Trade name is Karate. Approximately 32 percent of the cotton acres receive an application of cyhalothrin each year to control larvae and adults of the bollworm and tobacco budworm. The majority of applications are made aerially. Application rates average 0.03 pounds a.i. per acre. Approximately 2 to 3 applications are made each growing season. The preharvest interval is 21 days. The restricted-entry interval is 24 hours.
Profenofos
Trade name is Curacron 8E. Approximately 21 percent of the cotton acres receive an application of profenofos each year to control larvae and adults of the bollworm and tobacco budworm. The majority of applications are made by air. Application rates average 0.6 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 30 days. The restricted-entry interval is 48 hours.
Esfenvalerate
Trade name is Asana XL. Approximately 15 percent of the cotton acres receive an application of esfenvalerate each year to control larvae and adults of the bollworm and tobacco budworm. The majority of applications are made aerially. Application rates average 0.04 pounds a.i. per acre. Approximately 3 to 4 applications are made each growing season. The preharvest interval is 21 days. The restricted-entry interval is 12 hours.
Thiodicarb
The trade name is Larvin 3.2. Approximately 11 percent of the cotton acres receive an application of thiodicarb each year to control larvae and adults of the bollworm and tobacco budworm. Applications are made by ground and air with the majority applied aerially. Application rates average 0.6 pounds a.i. per acre. Approximately 1.2 applications are made each growing season. The preharvest interval is 28 days. The restricted-entry interval is 12 hours.
Cypermethrin
Trade names are Ammo 2.5EC and Ammo WSB. Approximately 10 percent of the cotton acres receive an application of cypermethrin each year to control larvae and adults of the bollworm and tobacco budworm. Applications are made by ground and air with the majority applied by ground equipment. Application rates average 0.06 pounds a.i. per acre. Approximately 2 to 3 applications are made each growing season. The preharvest interval is 14 days. The restricted-entry interval is 12 hours.
Methomyl
Trade names are Lannate SP and Lannate LV. Approximately 9 percent of the cotton acres receive an application of methomyl each year to control larvae and adults of the bollworm and tobacco budworm. Applications are made by ground and air with the majority applied by air. Application rates average 0.35 pounds a.i. per acre. Approximately 1 to 3 applications are made each growing season. The preharvest interval is 15 days. The restricted-entry interval is 72 hours.
Zeta-Cypermethrin
Trade name is Fury 1.5EC. Approximately 8 percent of the cotton acres receive an application of zeta-cypermethrin each year to control larvae and adults of the bollworm and tobacco budworm. Applications are made by ground and air with the majority applied aerially. Application rates average 0.04 pounds a.i. per acre. Approximately 5 to 6 applications are made each growing season. The preharvest interval is 14 days. The restricted-entry interval is 12 hours.
Tralomethrin
Trade names are Scout X-Tra, and Scout X-Tra Gel. Approximately 7 percent of the cotton acres receive an application of tralomethrin each year to control larvae and adults of the bollworm and tobacco budworm. The application method is evenly divided between air and ground. Application rates average 0.02 pounds a.i. per acre. Approximately 7-8 applications are made each growing season. The preharvest interval is 28 days. The restricted-entry interval is 24 hours.
Sulprofos
Trade name is Bolstar 6. Approximately 5 percent of the cotton acres receive an application of sulprofos each year to control larvae and adults of the bollworm and tobacco budworm. Applications are made by ground and air. Application rates average 0.75 pounds a.i. per acre. Approximately 2 to 3 applications are made each growing season. The preharvest interval is 14 days. The restricted-entry interval is 24 hours.
Chlorpyrifos
Trade name is Lorsban 4E. Approximately 1 percent of the cotton acreage receives an application of chlorpyrifos each year to control larvae and adults of the bollworm and tobacco budworm. Applications are made by ground and air with the majority applied with ground equipment. Application rates average 0.42 pounds a.i. per acre. Approximately 2 to 3 applications are made each growing season. The preharvest interval is 14 days. The restricted-entry interval is 24 hours.
Cultural Control Practices
Transgenic B.t. cotton.varieties.
Biological Controls
Monitoring bollworm and tobacco budworm populations using pheromone traps.
Other Issues
In the long term, the Boll Weevil Eradication Program should result in a reduction in the need for pesticides to control the bollworm and tobacco budworm.
THRIPS
Thrips are a common (i.e., yearly) problem for most cotton producers in Arkansas. Thrips infest cotton in the young seedling stage and severe thrips damage can stunt growth and reduce yield potential. As a result, most cotton is treated with an in-furrow insecticide to prevent the development of damaging populations and consequently thrips are rarely a devastating problem in Arkansas cotton.
The damage done by the pest: Larvae and adults suck plant juices from the tender terminals. The first targets of thrips moving into early cotton are the seed leaves, which become distorted or crinkled. Feeding damage can reduce stands enough to force replanting in extreme cases. Thrips feeding also can set back stand maturity. In most cases, the seedlings can grow out of the first stage of damage. Where feeding punctures are numerous enough, cotton may be triggered into a period of erratic habit and growth.
Percentage of infested acres: The average percentage of thrips infested cotton acres was 95.1% from 1996-1998.
Life cycle: Egg - four days; larva - six days, molting twice; pupa - four days; egg to adult - 14 days average. These pests overwinter in the pupa stage in plant trash. They begin reproducing in early spring in non-cotton host plants, such as grains, early blooming weeds, and legumes. Once the early host plants toughen, thrips move quickly into cotton fields. In many areas of the Cotton Belt, thrips migrate into cotton about the time wheat is cut. When the pests migrate, late-planted cotton is one of their chief targets since the crop is tender and offers easy feeding.
Critical timing of control measures: Must be treated early either with an in-furrow application at planting or a foliar application soon after the cotton plant emerges.
Yield losses attributed to pest: The average yield loss due to thrips was 0.51% from 1996-1998. Yield loss estimates do not include the costs associated with controlling or managing the pest.
Chemical Control
Disulfoton
Trade names are Di-Syston 15G and Di-Syston 8. Approximately 20 percent of the cotton acres are treated each year to control thrips. All applications are in-furrow treatments applied with ground equipment. Application rates average 0.83 pounds a.i. per acre. A single application is the norm. The preharvest interval is not applicable for in-furrow treatments. The restricted-entry interval is 48 hours.
Aldicarb
The trade is Temik 15G. Approximately 35 percent of the cotton acres are treated each year to control thrips. All applications are in-furrow treatments applied with ground equipment. Application rates average 0.41 pounds a.i. per acre. A single application is the norm. The preharvest interval is 90 days. The restricted-entry interval is 48 hours.
Acephate
Trade names are Orthene 90S and Orthene 75S. Approximately 11 percent of the cotton acres are treated at planting each year to control thrips. Application methods include seed treatments and in-furrow sprays with ground equipment. Application rates average 0.57 pounds a.i. per acre. The preharvest interval is not applicable for these "at planting" treatments. A single application is the norm. The restricted-entry interval is 24 hours.
Foliar applications of acephate are made later in the season to control thrips. Approximately 7 percent of the cotton acres are treated (aerially or by ground) with foliar applications of acephate. Application rates average 0.2 a.i. per acre. The preharvest interval is 21days. The restricted-entry interval is 24 hours.
Phorate
The trade name is Thimet 20-G. Approximately 6 percent of the cotton acres are treated each year to control thrips. All applications are in-furrow treatments applied with ground equipment. Application rates average 0.6 pounds a.i. per acre. A single application is the norm. The preharvest interval is 60 days. The restricted-entry interval is 48 hours.
Dicrotophos
The trade name is Bidrin 8E. Approximately 15 percent of the cotton acres receive a foliar application of dicrotophos each year to control thrips. Applications are made by ground and air. Application rates average 0.2 pounds a.i. per acre. The preharvest interval is 30 days. The restricted-entry interval is 48 hours.
Dimethoate
Trade names are Dimethoate 4 EC, 5LB Dimethoate, and Dimethoate 400. Approximately 7 percent of the cotton acres receive a foliar application of dimethoate each year to control thrips. Application rates average 0.2 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 14 days. The restricted-entry interval is 48 hours.
Cultural Control Practices
Some cotton varieties are more tolerant than others to thrips injury.
PLANT BUGS
Although they are a problem statewide, plant bugs are a more common problem in northern Arkansas. Lower plant bug populations in southern cotton growing areas are the result of more frequent use of insecticides for the control of the Heliothine complex and boll weevil. These treatments for bollworm, tobacco budworm and boll weevil also reduce the plant bug populations and fewer treatments are needed in south Arkansas in most years.
The damage done by the pest: All plant bugs have piercing mouthparts used to suck plant juices. Pinhead squares are primary targets. Soon after damage, the small squares turn brown and shed. Pre-squaring cotton is not safe though, since these insects attack growing portions of the plants and inflict serious damage even before square formation. Plant bugs, in this case, damage the stems and the young, tender terminals of the cotton plant. This injury can be serious enough to cause the plants to shift into exaggerated growth, with cotton branches becoming long and whip-like. In many cases, the cotton never really recovers. Damage symptoms sometimes cause "crazy cotton" where plants are severely distorted and stay in a pattern of fruitless growth for several weeks.
Severe infestations often develop quickly because these pests may build up into a massive population on another host, such as alfalfa or along roadsides. When the first host plant is cut or becomes tough, plant bugs migrate quickly into cotton and growers are faced with a full-blown plant bug problem just a day or two after checking clean fields. Flowers also are attacked by some plant bug species, causing warty growths on flower petals and brown spots on stamens and pistils. Plant bugs lay eggs inside cotton stems near the top of the plant. The pests usually lay very small eggs in groups that normally are impossible to detect.
Percentage of infested acres: The average percentage of plant bug infested cotton acres was 92.5% from 1996-1998.
Life cycle: The rapid plant bug and tarnished plant bug: eggs - 10 days; nymphs - 15 to 20 days; number of life stages - five. Clouded plant bug: eggs - 12 to 14 days; nymphs - 10 to 18 days; number of life stages - five.
All plant bugs are multiple-host insects and spend most of the season on other hosts, which they prefer over cotton. Tarnished and rapid plant bugs overwinter as adults in ground trash near host plants. The clouded plant bug overwinters in the egg state in the stems and stalks of host plants of various kinds. These pests are referred to as "true bugs" by entomologists because they do not pass through a larval or worm stage, and they do not go into the pupa or resting stage. When true bugs hatch, they resemble the adults except for size and often the absence of wings.
Critical timing of control measures: In the first two weeks of squaring, treat for plant bugs if square set is 75% or less and plant bugs are present. If small square set is less than 75%, treat for 1 plant bug per 3 row feet. After the last week in June in north Arkansas and first week of July in south Arkansas, if small square set is less than 85%, treat for 1 bug on 3 row feet. Treat for 1 plant bug per row foot (14,000 per acre) on normal fruiting fields.
Yield losses attributed to pest: The average yield loss due to plant bugs was 1.5% from 1996-1998. Yield loss estimates do not include the costs associated with controlling or managing the pest.
Chemical Control
Oxamyl
Trade names are Vydate C-LV and Vydate L. Approximately 31 percent of the cotton acres receive an application of oxamyl each year to control plant bugs. Applications are made by ground and air with the majority applied with ground equipment. Application rates average 0.25 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 21 days for Vydate L and 14 days for Vydate C-LV. The restricted-entry interval for both formulations is 48 hours.
Dicrotophos
The trade name is Bidrin 8E. Approximately 10 percent of the cotton acres receive an application of dicrotophos each year to control plant bugs. Applications are made by ground and air with the majority applied with ground equipment. Application rates average 0.24 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 30 days. The restricted-entry interval is 48 hours.
Dimethoate
Trade names are Dimethoate 4 EC, 5LB Dimethoate, and Dimethoate 400. Approximately 4 percent of the cotton acres receive an application of dimethoate each year to control plant bugs. The majority of applications are made with ground equipment. Application rates average 0.16 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 14 days. The restricted-entry interval is 48 hours.
Sulprofos
Trade name is Bolstar 6. Approximately 2 percent of the cotton acres receive an application of sulprofos each year to control plant bugs. The majority of applications are made with ground equipment. Application rates average 0.84 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 14 days. The restricted-entry interval is 24 hours.
Acephate
Trade names are Orthene 90S and Orthene 75S. Approximately 2 percent of the cotton acres receive an application of acephate each year to control plant bugs. The type of application is evenly divided between ground and air equipment. Application rates average 0.3 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 21 days. The restricted-entry interval is 24 hours.
Chlorpyrifos
Trade name is Lorsban 4E. Approximately 1 percent of the cotton acreage receives an application of chlorpyrifos each year to control plant bugs. Applications are made by ground and air with the majority applied with ground equipment. Application rates average 0.31 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 14 days. The restricted-entry interval is 24 hours.
Cultural Control Practices
Thick stands of cotton tend to have increased numbers of plant bugs.
APHIDS
Aphids are a secondary pest in cotton. Aphids tend to be a greater problem in cotton when early applications of insecticides have been made to reduce the overwintering boll weevil populations. The insecticides destroy beneficial parasites and predators that normally suppress aphid populations. In some years aphids have cause severe problems for cotton growers.
Frequency of occurrence: Aphids tend to be a frequent pest of a portion of Arkansas cotton each year.
The damage done by the pest: Heavy infestations cause curling or crinkling of leaves. Aphids feed on the youngest, most tender growth and, when present in large numbers, will cover terminals. During the principal blooming period, aphids may cause older leaves to turn yellow and shed. Severe infestations can cause heavy yield/quality losses.
Percentage of infested acres: The average percentage of aphid infested cotton acres was 59.4% from 1996-1998.
Life cycle: Female aphids give birth to live young. Females continuously reproduce without a male. The pests can multiply rapidly under high temperatures and may develop the equivalent of a new generation every five days.
Critical timing of control measures: Treat when populations are building and aphids are present on approximately 50% of the plants. Aphid treatments will be more effective when applied in combinations. Do not apply pyrethroids prior to July 1. Use systemic in-furrow insecticides at planting to suppress early season aphids.
Yield losses attributed to pest: The average yield loss due to plant bugs was 0.17% from 1996-1998. Yield loss estimates do not include the costs associated with controlling or managing the pest.
Chemical Control
Dicrotophos
The trade name is Bidrin 8E. Approximately 7 percent of the cotton acres receive an application of dicrotophos each year to control aphids. Applications are made by ground and air with the majority applied with ground equipment. Application rates average 0.27 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 30 days. The restricted-entry interval is 48 hours.
Methyl Parathion
Trade names are Methyl Parathion 4E and Penncap M. Approximately 5 percent of the cotton acres receive an application of methyl parathion each year to control aphids. The type of application is equally divided between air and ground equipment. Application rates average 0.25 pounds a.i. per acre. Approximately 1 application is made each growing season. The preharvest interval is 7 days. The restricted-entry interval is 48 hours.
Chlorpyrifos
Trade name is Lorsban 4E. Approximately 5 percent of the cotton acres receive an application of chlorpyrifos each year to control aphids. Applications are made by ground and air with the majority applied by air. Application rates average 0.39 pounds a.i. per acre. Approximately 1 application is made each growing season. The preharvest interval is 14 days. The restricted-entry interval is 24 hours.
Endosulfan
Trade names are Thiodan 3EC, Thiodan 50WP, Thiodan Cottonseed Oil, and Thiodan WSP. Approximately 4 percent of the cotton acres receive an application of endosulfan each year to control aphids. The application type is evenly divided between air and ground equipment. Application rates average 0.38 pounds a.i. per acre. Approximately 1 application is made each growing season. The preharvest interval statement on the label is "Do not apply after bolls open." The restricted-entry interval is 24 hours.
Methomyl
Trade names are Lannate SP and Lannate LV. Approximately 3 percent of the cotton acres receive an application of methomyl each year to control aphids. Applications are made by ground and air with the majority applied with ground equipment. Application rates average 0.15 pounds a.i. per acre. Approximately 1 to 2 applications are made each growing season. The preharvest interval is 15 days. The restricted-entry interval is 72 hours.
Bifenthrin
Trade name is Capture 2EC. Approximately 2 percent of the cotton acres receive an application of bifenthrin each year to control aphids. The application type is evenly divided between air and ground equipment. Application rates average 0.04 pounds a.i. per acre. Approximately 1 application is made each growing season. The preharvest interval is 14 days. The restricted-entry interval is 12 hours.
Imidacloprid
Trade name is Provado. Approximately 15 percent of the cotton acres receive an application of imidacloprid each year to control aphids. Applications are made with both ground and aerial equipment. Application rates range from 0.025 to 0.049 lbs a.i. per acre. The preharvest interval is 14 days. The restricted-entry interval is 12 hours.
Biological Controls
The aphid fungus is very effective in reducing aphid populations. The aphid fungus usually can occur in early to mid-July and before treatments are applied, fields should be checked for the fungus. If the fungus is present, it is recommended to not treat with insecticides for aphid control.
OTHER INSECT PESTS OF COTTON
Other secondary pests such as spider mites, cutworms, stink bugs, beet armyworms and fall armyworms occur sporadically throughout the state and do not occur in economically damaging numbers every year. Spider mite outbreaks occur along ditch banks and roadways where the spider mites overwinter on winter weeds and other host plants. Spider mites are a greater problem during growing seasons which average less than the expected rainfall. Cutworms attack newly emerged plants by cutting the young plant at the soil line and pests on field by field basis. Rarely are large numbers of acres affected by cutworms. Beet armyworms and fall armyworms occur primarily in south Arkansas during late summer. Neither species overwinters in Arkansas and therefore must migrate into Arkansas during the summer months. Populations of beet armyworms and fall armyworms rarely build up to large populations until late summer. Stinkbugs are generally more of a problem in cotton fields that have received few insecticide applications. Since most cotton production in Arkansas normally requires several insecticide applications for other pests, the stinkbug seldom becomes a problem in Arkansas.
Several diseases are economically important in Arkansas cotton production. Pathogen levels, seedling vigor, weather, and environmental conditions all affect the incidence and severity of disease each year. Most of the major cotton diseases are soil-borne and survive from year to year in the cotton field. The causal agents that cause seedling diseases include Pythium spp., Fusarium spp., Rhizoctonia solani, and Thielaviopsis basicola. These seedling disease pathogens may cause disease individually or they may interact to form a disease complex that can be more severe than the individual pathogen effects. Symptoms of seedling disease include pre-germination decay of the seed, decay of the seedling on the way to soil surface (pre-emergence damping off), partial or complete girdling of the emerged seedling at or near the soil surface and seedling root rot. Seedling diseases caused an average yield loss of approximately 3.75%, beyond any control measures, in Arkansas cotton (1995-1998). Fungicides are generally effective in controlling most seedling diseases.
Fusarium wilt (Fusarium oxysporum f. sp. vasinfectum) and Verticillium wilt (Verticillium dahliae) both may affect cotton in Arkansas. The significance of these diseases in the cotton crop varies from year to year. Yield losses to Verticillium wilt averaged 2.25% and yield losses due to Fusarium wilt averaged 1.1% (1995-1998). Fusarium wilt is often associated with the root knot nematode. This disease may be controlled to some degree using resistant varieties, although when nematodes are also present even resistant varieties may exhibit moderately severe disease. Practices that reduce nematode populations in cotton along with the use of Fusarium wilt resistant cultivars are effective in controlling this disease. Planting tolerant varieties, crop rotation, avoiding deep cultivation and careful management of irrigation and nitrogen can reduce Verticillium wilt severity. Pesticides are not effective in the control of Fusarium or Vericillium wilts.
Chemical Control
Metalaxyl
Trade name is Allegiance (seed treatment). Approximately 90 percent of the cotton acreage is planted using metalaxyl treated seed. Metalaxyl is effective in controlling Pythium seedling diseases. Application rates average 0.75 to 1.0 fluid ounce per 100 pounds of seed. The REI for Allegiance is 24 hours unless the seed is treated and the treated seed is soil incorporated or soil injected. The pre-harvest interval is not applicable.
Triadimenol
Trade name is Baytan (used as a seed treatment). Baytan is usually applied in combination with metalaxyl to seed for activity against R. solani in the mid-South and southeastern U.S. Application rates average 0.5 ounce per 100 pounds of seed. The restricted-entry interval and the preharvest interval are not applicable.
PCNB
Trade names are Terraclor 2E, Terraclor Super X (when combined with etridiazole), Terraclor Super X + Disyston EC, Terraclor 10G, Terraclor 75WP, and Ridomil Gold PC (mefenoxam + PCNB). At least 50 percent of the cotton acreage receives a single in-furrow PCNB application at planting to control seedling diseases. Application rates average from 0.5 to 1.0 pounds a.i. per acre. PCNB is effective in controlling Rhizoctonia. The REI for PCNB is 12 hours unless it is soil incorporated. The REI for PCNB + disulfoton is 48 hours unless it is soil incorporated. The pre-harvest interval is not applicable.
Mefenoxam
Trade name is Ridomil Gold PC (mefenoxam + PCNB). At least 50 percent of the cotton acreage receives a single in-furrow mefenoxam application at planting to control seedling diseases. Application rates range from 7 - 10 pounds per 13,000 linear feet of row. The REI for the product is 48 hours unless soil incorporated or soil injected. The pre-harvest interval is not applicable.
Iprodione
Trade name is Rovral. Rovral is effective as an in-furrow treatment for control of R.. solani. About 15% of the cotton acreage receives a single in-furrow iprodione application at planting, generally in combination with mefenoxam for control of both R.. solani and Pythium spp. Application rates range from 3.2 -8.7 ounces of Rovral per acre. The REI for the product is 24 hours. The preharvest interval is not applicable.
Two species of nematodes occur in Arkansas that can cause economic yield losses in cotton. These are the root-knot nematode (Meloidogyne incognita) and the reniform nematode (Rotylenchus reniformis). Statewide, approximately 30 percent of the cotton acreage in any given year is infested by one or the other of these two species, but in areas of historically high cotton acreage and long monoculture, the percentage of fields infested may reach 60 percent.
Root-knot is found in all areas of the state, while the reniform nematode has so far been found primarily in several counties in southeastern Arkansas. In the mid to late 1980s the reniform nematode was identified in isolated fields in southeast Arkansas. By 1993 the number of cotton fields identified with reniform nematode was found to be increasing in southeast Arkansas. By 1999 approximately 10-15% of the total cotton acreage in Arkansas was infested with reniform nematode. In certain counties as much as 40% of the cotton acreage is infested with the reniform nematode. Although the reniform nematode is still concentrated in southeast Arkansas it has spread as far north as the "boot heel" region of southeast Missouri
The average yield loss caused by these two nematodes species, beyond any control measures, on Arkansas cotton is 4.5% (1995-1998). Total field loss is possible in severe situations.
The symptoms associated with nematodes are often mistaken for other problems such as nutritional imbalance, soil compaction, and water stress. Characteristic root galls are associated with root-knot nematode infection, while reniform nematodes do not cause galls.
Crop rotation is generally the most cost-effective method of nematode control over time, but rotational crops may be of relatively low economic value. Production of rice, corn, grain sorghum, or peanut, or resistant soybean cultivars for one or two years in rotation with cotton may improve crop performance by lowering reniform nematode populations. Careful selection of rotation crops, based on the nematode species to be controlled, is essential.
There are two conventional cotton varieties with moderate resistance to root-knot nematodes (Stoneville LA 887 and Paymaster 1560), but none with resistance to reniform nematodes. Transgenic cotton varieties are currently being evaluated for nematode resistance.
Nematode Control
Aldicarb
Trade name is Temik 15G. Approximately 25 percent of the cotton acreage receives a single application of aldicarb at planting for nematode control, although about 50% of the acreage is treated at lower rates for early season insect suppression. Application rates range from 0.5 to 1.5 lbs a.i. per acre. The REI for aldicarb is 48 hours unless it is soil incorporated. The pre-harvest interval is 90 days.
Fenamiphos
Trade names are Nemacur 15% and Nemacur 3. A very small percentage of the cotton acreage receives a single application of fenamiphos at planting. Application rates range from 1 to 2 pounds a.i. per acre. The REI for fenamiphos is 48 hours unless it is soil incorporated. The pre-harvest interval is not applicable.
The key to weed management in cotton is providing the seedling cotton plant with conditions that allow cotton to outgrow weeds, thus establishing a height difference for directed sprays. While pre-plant and pre-emergence herbicides must be used to control or suppress weed growth, the application of timely post-directed herbicides is often required to maintain a successful weed control program. Cultural practices that promote rapid germination and vigorous cotton seedling growth are very important in allowing timely post-emergence applications. The weed species composition of the cotton crop is important in selection of the best weed control program. The proper identification of the weed complex will determine the best program to use.
The pre-plant herbicides are utilized to control several weeds including annual grass suppression, morningglory suppression, and seedling johnsongrass control. The pre-emergence herbicides are used to control the broadleaf complex including prickly sida, morningglory, and cocklebur. The post-emergence herbicide applications are directed toward control of grasses and broadleaf weeds that occur including johnsongrass, annual grasses, cocklebur and morningglory.
ANNUAL GRASSES: Barnyardgrass (Echinocloa crus-galli), Crabgrass (Digitaria spp.), Broadleaf signalgrass (Brachiaria platyphylla), Goosegrass (Eleusine indica), Foxtail (Setaria spp.), Seedling johnsongrass (Sorghum halapense), Fall panicum (Panicum dichotomiflorum).
Frequency of occurrence: Every year.
The damage done by the pests: Competition with the cotton crop for water, sunlight, and nutrients. In addition, weed seeds and plant residues in the harvested cotton can result in economic loss due to grade reduction.
Percentage of infested acres (1998): Barnyardgrass - 2.1%, Crabgrass - 36.8%, Broadleaf signalgrass - 4.2%, Goosegrass - 31.6%, Seedling johnsongrass - 36.8%, Fall panicum - 1.1%.
Life cycle: Summer annuals
Critical timing of control measures: To best prevent cotton yield losses, annual grasses should be controlled as early as possible. Preplant incorporated and preemergence applications of these herbicides provide good early season control of the annual grasses. Post emergence applications of certain herbicides will also control the annual grasses that escape early season applications.
Yield losses attributed to pest (1998): Barnyardgrass - 1.0%, Crabgrass - 6.0%, Broadleaf signalgrass - 1.0%, Goosegrass - 1.0%, Seedling johnsongrass - 10%, Fall panicum - 1.0%. Yield loss estimates do not include the costs associated with controlling or managing the pest(s).
Chemical Control - Preplant Incorporated Treatments for Grasses
Trifluralin
Trade names include Treflan HFP, Treflan TR-10 (granular), Tri-4 HF, Trifluralin 4EC, Trifluralin HF. Approximately 45 percent of the cotton acreage receives a single preplant incorporated trifluralin application each year. Most applications are made by ground equipment. Application rates average 0.62 pounds a.i. per acre. Trifluralin effectively controls all of the listed annual grasses except goosegrass. The typical REI for trifluralin on cotton is 12 hours. Pre-harvest intervals are not applicable.
Norflurazon
Trade name is Zorial Rapid 80. Approximately 30 percent of the cotton acreage receives a single preplant incorporated norflurazon application each year. Most applications are made by ground equipment. Application rates average 0.56 pounds a.i. per acre. Norflurazon effectively controls all of the listed annual grasses. The REI for norflurazon on cotton is 12 hours unless it is soil incorporated (i.e., preplant incorporated). If soil incorporated the REI is not applicable in most cases. Pre-harvest intervals are not applicable.
Pendimethalin
Trade name is Prowl 3.3 EC. Approximately 35 percent of the cotton acreage receives a single preplant incorporated pendimethalin application each year. Most applications are made by ground equipment. Application rates average 0.58 pounds a.i. per acre. Pendimethalin effectively controls all of the listed annual grasses except goosegrass. The typical REI for pendimethalin on cotton is 12 hours unless it is soil incorporated (i.e., preplant incorporated). If soil incorporated the REI is not applicable in most cases. Pre-harvest intervals are not applicable.
Fluometuron
Trade names are Cotoran 4L and Cotoran DF. Approximately 1 percent of the cotton acreage receives a single preplant incorporated fluometuron application each year. Most applications are made by ground equipment. Application rates average 0.8 pounds a.i. per acre. Fluometuron effectively controls all of the listed annual grasses except barnyardgrass and seedling johnsongrass. The REI for fluometuron on cotton is 24 hours unless it is soil incorporated (i.e., preplant incorporated). If soil incorporated the REI is not applicable in most cases. The pre-harvest interval is 60 days.
Chemical Control - Preemergence Treatments for Grasses
Metolachlor
Trade names are Dual, Dual 8E, and Dual II. Approximately 4 percent of the cotton acreage receives a single preemergence metolachlor application each year. Most applications are made by ground equipment. Application rates range from 0.66 pounds a.i. per acre. Metolachlor effectively controls all of the listed annual grasses except seedling johnsongrass. The REI for metolachlor is 12 hours. Pre-harvest intervals are not applicable.
Fluometuron
Trade names are Cotoran 4L and Cotoran DF. Approximately 75 percent of the cotton acreage receives a single preemergence fluometuron application each year. Most applications are made by ground equipment. Application rates average 0.67 pounds a.i. per acre. Fluometuron effectively controls all of the listed annual grasses except barnyardgrass and seedling johnsongrass. The REI for fluometuron on cotton is 24 hours unless it is soil incorporated (i.e., preplant incorporated). If soil incorporated the REI is not applicable in most cases. The pre-harvest interval is 60 days.
Clomazone
Trade name is Command 3ME. Approximately 10 percent of the cotton acreage receives a single preemergence clomazone application each year. Most applications are made by ground equipment. Application rates average 0.44 pounds a.i. per acre. Clomazone effectively controls all of the listed annual grasses. The REI for clomazone on cotton is 12 hours unless it is soil. If soil incorporated the REI is not applicable in most cases. The pre-harvest interval is 65 days.
Norflurazon
Trade name is Zorial Rapid 80. Approximately 40 percent of the cotton acreage receives a single preemergence norflurazon application each year. Most applications are made by ground equipment. Application rates average 0.51 pounds a.i. per acre. Norflurazon effectively controls all of the listed annual grasses. The REI for norflurazon on cotton is 12 hours unless it is soil incorporated (i.e., preplant incorporated). If soil incorporated the REI is not applicable in most cases. Pre-harvest intervals are not applicable.
Pendimethalin
Trade name is Prowl 3.3 EC. Approximately 10 percent of the cotton acreage receives a single preemergence pendimethalin application each year. Most applications are made by ground equipment. Application rates average 0.37 pounds a.i. per acre. Pendimethalin effectively controls all of the listed annual grasses except goosegrass. The typical REI for pendimethalin on cotton is 12 hours unless it is soil incorporated (i.e., preplant incorporated). If soil incorporated the REI is not applicable in most cases. Pre-harvest intervals are not applicable.
Chemical Control - Postemergence Treatments for Grasses
Cyanazine
Trade name is Bladex 4L and Bladex 90DF. Approximately 58 percent of the cotton acreage receives a postemergence cyanazine application each year (on 33 percent of the acres it is tank-mixed with MSMA). Applications are made post-directed by ground equipment and 1 to 2 applications per year is the average. Application rates average 0.52 pounds a.i. per acre. Cyanazine effectively controls all of the listed annual grasses except seedling johnsongrass. The REI for cyanazine is 12 hours. The pre-harvest interval is 54 days.
MSMA/DSMA
Many formulations exist (i.e., many trade names). Approximately 85 percent of the cotton acreage receives a postemergence MSMA or DSMA application each year. Applications are made post-directed by ground equipment and 1 to 2 applications each year is the average. The two herbicides are often tank-mixed with another postemergence herbicide. By itself, MSMA and DSMA are effective in controlling all of the listed annual grasses except for goosegrass. Application rates average 1.4 pounds a.i. per acre. The REI for MSMA and DSMA is 12 hours. The pre-harvest interval is not applicable.
Prometryn
Trade name is Caparol and Cotton-Pro. Approximately 35 percent of the cotton acreage receives a postemergence prometryn application each year (on 20 percent of the acres it is tank-mixed with MSMA). Applications are normally tank-mixed with other herbicides and made post-directed (postemergence) by ground equipment and 1 to 2 applications each year is the average. Application rates average 0.45 pounds a.i. per acre. Prometryn effectively controls all of the listed annual grasses. The REI for prometryn is 12 hours. The pre-harvest interval is not applicable.
Diuron
Trade names are Karmex and Direx. Approximately 11 percent of the cotton acreage receives a diuron application each year (on 10 percent of the acres it is tank-mixed with MSMA). Applications are normally tank-mixed with other herbicides and made post-directed (postemergence) by ground equipment and 1 to 2 applications each year is the average. Application rates average 0.48 pounds a.i. per acre. Diuron effectively controls crabgrass, barnyardgrass, foxtail, and seedling johnsongrass. The REI for diuron is 12 hours. The pre-harvest interval is not applicable.
Glyphosate
Trade name is Roundup Ultra. Approximately 40 percent (represents the percentage of acres planted with glyphosate-resistant cotton) of the total cotton acreage receives at least one postemergence application of glyphosate. Approximately two-thirds of the glyphosate treated acres receive a second application of the herbicide. As a postemergence application for annual grasses and broadleaves glyphosate can only be applied to glyphosate-resistant cotton varieties. Glyphosate is effective in controlling all of the listed grass and broadleaf weeds except for spurred anoda, smartweed, and yellow nutsedge. Application rates average 0.75 pounds a.i. per acre. The REI for glyphosate is 4 hours. The pre-harvest interval is 7 days.
Fluometuron
Trade names are Cotoran 4L and Cotoran DF. Approximately 65 percent of the cotton acreage receives a postemergence fluometuron application each year (on 40 percent of the acres it is tank-mixed with MSMA). Most applications are made by ground equipment. Application rates average 0.65 pounds a.i. per acre. As a postemergence treatment, there are normally 1 to 2 applications per year. Fluometuron effectively controls all of the listed annual grasses except barnyardgrass and seedling johnsongrass. The REI for fluometuron on cotton is 24 hours. The pre-harvest interval is 60 days.
Quizalofop (trade name: Assure II)
Clethodim (Select 2EC)
Fluazifop + Fenoxaprop (Fusion)
Fluazifop (Fusilade DX)
Sethoxydim (Poast Plus)
Approximately 25 percent of the cotton acreage receives either a broadcast over-the-top application or is "spot" treated with of one of the grass herbicides listed above.
Quizalofop: Rates - 0.031 to 0.063 lb a.i. per acre, PHI - 80 days, REI - 12 hours
Clethodim: Rates - 0.094 to 0.25 lb a.i. per acre, PHI - 60 days, REI - 24 hours
Fluazifop: Rate - 0.188 lb a.i. per acre, PHI - 90 days, REI - 12 hours
Fluazifop + Fenoxaprop: Rates - 0.094 to 0.188 lb a.i. per acre (fluazifop) and 0.026 to 0.053 lb a.i. per acre (fenoxaprop), PHI - 90 days, REI - 24 hours
Sethoxydim: Rates - 0.2 to 0.3 lb a.i. per acre, PHI - 40 days, REI - 12 hours
BROADLEAVES: Prickly sida (Sida spinosa), Spurred Anoda (Anoda cristata), Velvetleaf (Abutilon theophrasti), Cocklebur (Xanthium strumarium), Pitted Morningglory (Ipomoea lacunosa), Entireleaf Morningglory (Ipomea hederacea var. integriuscula), Pigweed (Amaranthus spp. ), Palmer Amaranth (Amaranthus palmeri), Spotted Spurge (Euphorbia maculata), Smartweed (Polygonum spp.), Sedge (Cyperus spp.)
Frequency of occurrence: Every year.
The damage done by the pests: Competition with the cotton crop for water, sunlight, and nutrients. Weed seeds and plant residues in the harvested cotton can result in economic loss due to grade reduction. In addition, some weeds (e.g., morningglory) can adversely affect the harvesting efficiency of the cotton picker.
Percentage of infested acres (1998): Prickly sida - 52.6%, Spurred anoda - 1.1%, Velvetleaf - 1.1%, Cocklebur - 31.6%, Morningglories - 78.9%, Pigweed - 31.6%, Spotted spurge - 42.1%, Smartweed - 2.6%, Sedges- 4.2%.
Life cycle: Summer annuals
Critical timing of control measures: To best prevent cotton yield losses, broadleaves should be controlled as early as possible. Preplant incorporated and preemergence applications of these herbicides provide good early season control of most broadleaves. Postemergence applications of certain herbicides will also control the broadleaves that escape early season applications.
Yield losses attributed to broadleaves: Prickly sida - 10%, Spurred anoda - 2%, Velvetleaf - 1%, Cocklebur - 10%, Morningglories - 25%, Pigweed - 10, Spotted spurge - 14%, Smartweed - <1% , Sedges - 5%. Yield loss estimates do not include the costs associated with controlling or managing the pest(s).
Chemical Control - Preplant Incorporated Treatments for Broadleaves
Trifluralin
Trade names include Treflan HFP, Treflan TR-10 (granular), Tri-4 HF, Trifluralin 4EC, Trifluralin HF. Approximately 45 percent of the cotton acreage receives a single preplant incorporated trifluralin application each year. Most applications are made by ground equipment. Application rates average 0.63 pounds a.i. per acre. Trifluralin is effective in controlling pigweed, purslane, and lambsquarter. The typical REI for trifluralin on cotton is 12 hours. Pre-harvest intervals are not applicable.
Norflurazon
Trade name is Zorial Rapid 80. Approximately 30 percent of the cotton acreage receives a single preplant incorporated norflurazon application each year. Most applications are made by ground equipment. Application rates average 0.56 pounds a.i. per acre. Norflurazon is effective in controlling prickly sida, spurred anoda, pigweeds, purslane, hophornbeam copperleaf, ragweed, lambsquarter, and flatsedge. The REI for norflurazon on cotton is 12 hours unless it is soil incorporated (i.e., preplant incorporated). If soil incorporated the REI is not applicable in most cases. Pre-harvest intervals are not applicable.
Fluometuron
Trade names are Cotoran 4L and Cotoran DF. Approximately 1 percent of the cotton acreage receives a single preplant incorporated fluometuron application each year. Most applications are made by ground equipment. Application rates average 0.8 pounds a.i. per acre. Fluometuron is normally tank-mixed with trifluralin when applied as a preplant treatment. This tank mix is effective in controlling pigweeds, purslane, hophornbeam copperleaf, ragweed, and lambsquarter. The REI for fluometuron on cotton is 24 hours unless it is soil incorporated (i.e., preplant incorporated). If soil incorporated the REI is not applicable in most cases. The pre-harvest interval is 60 days.
Pendimethalin
Trade name is Prowl 3.3 EC. Approximately 35 percent of the cotton acreage receives a single preplant incorporated pendimethalin application each year. Most applications are made by ground equipment. Application rates average 0.58 pounds a.i. per acre. Pendimethalin is effective in controlling pigweed, purslane, and lambsquarter. The typical REI for pendimethalin on cotton is 12 hours unless it is soil incorporated (i.e., preplant incorporated). If soil incorporated the REI is not applicable in most cases. Pre-harvest intervals are not applicable.
Chemical Control - Preemerge Treatments for Broadleaves
Fluometuron
Trade names are Cotoran 4L and Cotoran DF. Approximately 75 percent of the cotton acreage receives a single preemerge fluometuron application each year. Most applications are made by ground equipment. Application rates average 0.67 pounds a.i. per acre. Fluometuron is effective in controlling prickly sida, cocklebur, morningglories, pigweed, purslane, hophornbeam copperleaf, ragweed, lambsquarter, and flatsedge. The REI for fluometuron on cotton is 24 hours unless it is soil incorporated (i.e., preplant incorporated). If soil incorporated the REI is not applicable in most cases. The pre-harvest interval is 60 days.
Clomazone
Trade name is Command 3ME. Approximately 10 percent of the cotton acreage receives a single preemerge clomazone application each year. Most applications are made by ground equipment. Application rates average 0.44 pounds a.i. per acre. Clomazone is often tank-mixed with fluometuron when applied as a preemerge treatment. This tank mix is effective in controlling all of the listed broadleaves except for palmer amaranth and spotted spurge. The REI for clomazone on cotton is 12 hours unless it is soil. If soil incorporated the REI is not applicable in most cases. The pre-harvest interval is 65 days.
Norflurazon
Trade name is Zorial Rapid 80. Approximately 40 percent of the cotton acreage receives a single preemerge norflurazon application each year. Most applications are made by ground equipment. Application rates average 0.51 pounds a.i. per acre. Norflurazon is effective in controlling all of the listed broadleaves except for velvetleaf, cocklebur, morningglories, spotted spurge, and smartweed. The REI for norflurazon on cotton is 12 hours unless it is soil incorporated (i.e., preplant incorporated). If soil incorporated the REI is not applicable in most cases. Pre-harvest intervals are not applicable.
Chemical Control - Postemerge Treatments for Broadleaves
Cyanazine
Trade name is Bladex 4L and Bladex 90DF. Approximately 58 percent of the cotton acreage receives a postemergence cyanazine application each year (on 33% of the acres cyanazine is tank-mixed with MSMA). Applications are made post-directed by ground equipment and 1 to 2 applications per year is the average. Application rates average 0.52 pounds a.i. per acre. Cyanazine is effective in controlling all of the listed broadleaves except spurred anoda, velvetleaf, and smartweed. It is often tank-mixed with MSMA to provide additional grass control. The REI for cyanazine is 12 hours. The pre-harvest interval is 54 days.
Fluometuron
Trade names are Cotoran 4L and Cotoran DF. Approximately 65 percent of the cotton acreage receives a postemergence fluometuron application each year (on 40% of the acres fluometuron is tank-mixed with MSMA). Most applications are made by ground equipment and 1 to 2 applications per year is the average. Application rates average 0.67 pounds a.i. per acre. Fluometuron is effective in controlling prickly sida, cocklebur, morningglories, pigweed, purslane, hophornbeam copperleaf, ragweed, lambsquarter, and flatsedge. It is often tank-mixed with MSMA to provide additional grass control. The REI for fluometuron on cotton is 24 hours. The pre-harvest interval is 60 days.
Prometryn Trade name is Caparol 4L. Approximately 35 percent of the cotton acreage receives a postemergence prometryn application each year (on 20% of the acres prometryn is tank-mixed with MSMA). Most applications are made by ground equipment and there is an average of 1-2 applications each year. Application rates average 0.45 pounds a.i. per acre. Prometryn is effective in controlling all of the listed broadleaves except spurred anoda, velvetleaf, spotted spurge, and smartweed. It is often tank-mixed with MSMA to provide additional grass control. The REI for fluometuron on cotton is 12 hours.
Diuron
Trade names are Karmex and Direx. Approximately 11 percent of the cotton acreage receives a postemergence diuron application each year (on 10% of the acres diuron is tank-mixed with MSMA). Applications are normally tank-mixed with other herbicides such as MSMA (to provide additional grass control) and made post-directed (postemergence) by ground equipment and 1 to 2 applications each year is the average. Application rates average 0.48 pounds a.i. per acre. Prometryn is effective in controlling all of the listed broadleaves except spurred anoda, velvetleaf, spotted spurge, and smartweed. The REI for diuron is 12 hours. The pre-harvest interval is not applicable
Lactofen
Trade name is Cobra. Approximately 10 percent of the cotton acreage receives a postemergence lactofen + MSMA tank-mix application each year. Applications are made post-directed by ground equipment and 1 to 2 applications each year is the average. Application rates average 0.18 pounds a.i. per acre. Lactofen is effective in controlling all of the listed broadleaves except spurred anoda, palmer amaranth, and smartweed. It can be tank-mixed with MSMA to provide additional grass control. The REI for lactofen is 12 hours. The pre-harvest interval is 45 days.
Glyphosate
Trade name is Roundup Ultra. Approximately 30 percent (represents the percentage of acres planted with glyphosate-resistant cotton) of the total cotton acreage receives at least one postemergence application of glyphosate. Approximately two-thirds of the glyphosate treated acres receive a second application of the herbicide. As a postemergence application for annual grasses and broadleaves glyphosate can only be applied to glyphosate-resistant cotton varieties. Glyphosate is effective in controlling all of the listed grass and broadleaf weeds except for spurred anoda, smartweed, and yellow nutsedge. Application rates average 0.75 pounds a.i. per acre. The REI for glyphosate is 4 hours. The pre-harvest interval is 7 days.
Bromoxynil
Trade name is Buctril 4EC. Approximately 35 percent (represents the percentage of acres planted with bromoxynil-resistant cotton) of the total cotton acreage receives at least one application of bromoxynil each year. A small percentage of the bromoxynil treated acres receive a second application of the herbicide. As a post-directed application for broadleaves, bromoxynil can only be applied to bromoxynil-resistant cotton varieties. Bromoxynil effectively controls cocklebur, morningglories, hophornbeam copperleaf, ragweed, smartweed, and jimsonweed. Application rates average 0.375 pounds a.i. per acre. The REI for bromoxynil is 12 hours. The pre-harvest interval is 75 days.
Alternatives
Alternatives to pesticides for weed control in cotton include mechanical cultivation, hand labor, and flame cultivation. Virtually all of the cotton acres are mechanically cultivated to control weeds (broadleaves and grasses). Hand labor is used on approximately 34 percent of the cotton acreage to control weeds. Flame cultivation is used to control weeds on a small percentage of acres (0.2%).
Spot spraying is used on a small number of acres to control weeds. In these cases only the infested areas of a field receive a pesticide application.
Dr. Donald R. Johnson
Extension Entomologist
Coop. Ext. Ser., Univ. of Ark.
P.O. Box 391
Little Rock, AR 72203
Phone: 501-671-2229
Email: djohnson@uaex.edu
Dr. William C. Robertson
Extension Cotton Specialist
Coop. Ext. Ser., Univ. of Ark.
P.O. Box 391
Little Rock, AR 72203
Phone: 501-671-2186
Email: wrobertson@uaex.edu
Dr. Rick Cartwright
Extension Plant Pathologist
Coop. Ext. Ser., Univ. of Ark.
P.O. Box 391
Little Rock, AR 72203
Phone: 501-671-2228
Email: rcartwright@uaex.edu
Dr. Gus Lorenz
Extension IPM Coordinator
Coop. Ext. Ser., Univ. of Ark.
P.O. Box 391
Little Rock, AR 72203
Phone: 501-671-2191
Email: glorenz@uaex.edu
Dr. Ford L. Baldwin
Extension Weed Scientist
Coop. Ext. Ser., Univ. of Ark.
P.O. Box 391
Little Rock, AR 72203
Phone: 501-676-3124
Email: fbaldwin@uaex.edu
Dr. Terry Kirkpatrick
University of Arkansas Professor, Nematology
Southwest Research and Extension Center
362 Hwy 174
Hope, AR 71801
Phone: 870-777-9702 Ext. 111
Email: tkirkpat@uaex.edu
Compiled by:
Ples Spradley
Pesticide Assessment Specialist
Coop. Ext. Ser., Univ. of Ark.
P.O. Box 391
Little Rock, AR 72203
Phone: 501-676-3124
Email: pspradley@uaex.edu
Acknowledgements
We would like to thank the following University of Arkansas personnel for their input and review of this crop profile for cotton: Dr. Don Johnson, Extension Entomologist; Dr. Bill Robertson, Extension Agronomist; Dr. Rick Cartwright, Extension Plant Pathologist; Dr. Gus Lorenz, Extension Entomologist; Dr. Ford Baldwin, Extension Weed Scientist, and Dr. Terry Kirkpatrick, Professor, Plant Pathology. In addition, we would like to thank Ewell Welch, Director - Commodity and Public Policy and Gene Martin, Senior Market Analyst, both with Arkansas Farm Bureau, for their review of this crop profile.
Database and web development by the NSF Center for Integrated Pest Managment located at North Carolina State University. All materials may be used freely with credit to the USDA.