Crop Profile for Wheat in California
Prepared: March 2002
General Production Information
· California produces an average of 1.3 million tons of wheat per year. In 2000 red wheat accounted for 78% of the total acres planted, Durum™ accounted for 16% with the remaining 6% planted to white wheat (1).
· In 2000 the value of wheat in California was $161,660,900 (2).
· Cost of production varies from region to region. Depending on the cost of seed and inputs, the breakeven point for growers is $95.00 to $145.00 per acre (9).
· In 2000, 577,624 acres were harvested in California. The average yield was 2.65 ton /acre with an average price of $106/ton (2).
· In 1999, 549,704 acres were harvested in California. The average yield was 2.79 ton/acre with an average price of $93/ton (2).
· The total value of wheat grown in California in 2000 was $143,352,900. (10)
· California ranks 19 in U.S. wheat production providing 2% of the national production. (10)
Wheat is grown in almost every county in California. The predominate growing areas include the desert area in Southern California (18%), the San Joaquin Valley (50.%), and the Sacramento Valley (27%). Other areas include the northern intermountain region (2%) and the coastal areas (3%). (3) Each area has distinct climatic differences, crop rotation patterns and suitable wheat varieties. The varieties produced in each region have undergone extensive agronomic evaluation by private and public breeding programs. These programs are conducted in cooperation with the cooperative extension programs and growers.
General Production Regions
Wheat is grown throughout California. The state is broken into five production regions: northern intermountain area, Sacramento Valley, San Joaquin Valley, southern desert, and coastal areas. Hard red spring wheats are dominant in the north part of the state and are used for bread or general-purpose flour. The Durum-type wheats are produced in the southern and desert areas of California.
The majority of small grain acreage is irrigated. Soil moisture monitoring and irrigation scheduling are practiced to enhance water use efficiency. Dryland grain production is important along the eastern foothills of the Central Valley and the central and south coastal region.
Wheat crops are planted in the fall months from October to December and harvested from May 20 to September 1.
The monetary value does not necessarily show the true value of wheat in California. The decision to plant wheat is not only based on the economic return on the wheat crop itself, but often the benefits wheat offers in a rotational cropping system. Growers frequently plant wheat as a tool for disease control and soil conservation.
The vast majority of production acreage of wheat is treated with herbicides for broadleaf and grass weeds. Insect and disease applications of pesticides are made to a lesser degree due to the resistant varieties available reducing the need for fungicide applications.
Integrated Pest Management
California grain growers consider wheat an important crop within the rotation system of the diverse commodities grown in California. The value of crop rotation for weed and disease management is important in the IPM system. Other integrated pest management practices established and used for grain production include:
· Preplant cultivation to reduce weed population.
· Rotation into grain crops that better utilize soil residual fertilizers and particular nitrate nitrogen carried over from other crops.
· Use of established treatment threshold levels for insects and weeds to reduce unnecessary chemical usage.
The IPM practices used for grain production rely on the use of selective organophosphate insecticides and certain other chemicals when pest situations develop beyond the economic threshold levels. Without the current chemical tools available the implementation of IPM programs and their ability to be effective would be greatly reduced.
Label rates, re-entry intervals and pre-harvest intervals for all chemicals listed in this document are from labels. Many of the labels are contained in the Crop Protection Reference (6) or at http://www.cdms.net/manuf/manufac.asp. Percent of acres treated, average number of applications, median application rate, and total lb a.i. applied are from the California Department of Pesticide Regulation (7). The following data is for pesticide use on wheat grown for human consumption. See section at end of document for pesticide use on wheat grown for forage.
Russian Wheat Aphid: Diuraphis noxia
Bird Cherry-Oat Aphid: Rhopalosiphum padi
Greenbug: Schizaphis graminum
English Grain Aphid: Sitobion avenae
Rose Grass Aphid: Acyrthosiphum (Metopolophium) dirhodum
Corn Leaf Aphid: Rhopalosiphum maidis
Russian wheat aphid is small and pale green in color with an elongated spindle-shaped body. It can be distinguished from the other aphids by a second long tail-like process. Russian wheat aphid injects a toxin while feeding causing white, longitudinal streaks on the leaves and occasionally the stem. Plants are also stunted and with curled leaves. Heavily infested plants sometimes exhibit a flattened appearance, and occasionally, show a purple color. Leaves can curl and remain upright resembling a soda straw. The head may be distorted, assuming a fishhook appearance.
The bird cherry-oat aphid is the most common aphid found on cereals. It ranges in color from orange green to olive green to dark olive green and green black. Heavy populations cause a golden yellow streaking on the leaves. The flag may also curl up in a tight corkscrew fashion that can trap the awns resulting in a fishhook appearance to the head.
The greenbug is a green to yellow-green aphid with a dark green stripe down the middle of its back. It is easily confused with the rose grass aphid. Greenbug injects a toxin into the plant while feeding causing yellow spots or patches to appear on the leaves. Leaves or plants turn yellow as populations increase. Plants are damaged only if significant feeding occurs before tillering. Damage occurs mostly in the Imperial Valley, but can also occur in the San Joaquin Valley.
English grain aphid is reddish brown in color and appears later in the season than the other aphids. It causes very little damage to wheat, unless present in high numbers. It frequently colonizes the heads. The large amounts of honeydew produced by this aphid, particularly when in the head, may clog harvesting equipment.
Rose grass aphid and corn leaf aphid can be confused with greenbug. Both cause very minor damage to the crop.
All, but the Russian wheat aphid, are vectors of barley yellow dwarf virus (4).
Destroy and remove volunteer cereals to help reduce or delay the build-up of Russian wheat aphid and bird cherry-oat aphid populations. Regular watering can help prevent water-stressed plants that are more susceptible to and suffer greater damage from Russian wheat aphid. (4).
Natural enemies including lady beetles, syrphid fly larvae, parasitic wasps and a fungal disease can keep aphids associated with wheat from reaching damaging levels. However, this may not be the case for Russian wheat aphid and any chemical application to control this aphid may upset the population of natural enemies, causing outbreaks of other aphid species (4).
· Disulfoton - Label has a rate of up to 1 lb a.i./acre and a 60-day PHI. 48 or 72 hour REI. In 2000, 10,484 lb a.i. were used on 3.8% of California's wheat acreage an average of 1 time at a median application rate of 0.71 lb a.i./acre. (3,7)
· Dimethoate - Label has a rate of 0.17 - 0.38 lb a.i./acre and a 35-day PHI. 48-hour REI. In 2000, 4,139 lb a.i. were used on 3.3% of California's wheat acreage an average of 1 time at a median application rate of 0.32 lb a.i./acre. (3,7)
· Chlorpyrifos - Label has a rate of 0.25-0.5 lb a.i./acre and a 28-day PHI. 24-hour REI. In 2000, 1,139 lb a.i. were used on 0.5% of California's wheat acreage an average of 1 time at a median application rate of 0.50 lb a.i./acre. (3,7)
· Malathion - Label has a rate of 0.95-1.26 lb a.i./acre and a 7-day PHI. 12-hour REI. In 2000, 1,539 lb a.i. were used on 0.4% of California's wheat acreage an average of 1 time at a median application rate of 1.20 lb a.i./acre. (3,7)
· Methomyl - Label has a rate of 0.25-0.50 lb a.i./acre and a 7-day PHI. 48-hour REI. In 2000, 106 lb a.i. were used on 0.07% of California's wheat acreage an average of 1 time at a median application rate of 0.45 lb a.i./acre. (3,7)
Armyworm, Pseudaletia unipuncta
Western yellowstriped armyworm, Spodoptera praefica
Armyworms are pale green when young, maturing to greenish brown to black with stripes along the sides. Larvae of both species cause damage by eating leaves. Entire leaves may be consumed or damage may consist of notches chewed out of the leaves giving them a tattered look. Damage may occur when larvae hatch from eggs laid in the cereal crop or from larvae migrating into the cereal crop from an adjacent field (4).
If larvae are moving from field to field, a deep wide water-filled ditch between the two fields can help obtain some control until the migration stops (4).
Armyworms are attacked by a naturally-occurring parasitic wasp, Hyposoter sp. Pulling apart the larvae and looking for green parasite larvae can identify the parasitized worms. Viral diseases of armyworms may also be important natural control agents.
· Methomyl - See Aphids
· Malathion - See Aphids
Additional wheat insect pests that usually do not require chemical treatment include; stinkbugs, black grass bug, wheat stem maggot, wireworms, grasshoppers, mites and range crane fly.
Septoria Tritici Blotch of Wheat: Mycosphaerella graminicola and Septoria tritici
Septoria tritici blotch affects only wheat and is the most important foliar disease of wheat in the Sacramento and northern San Joaquin valleys. Foliar symptoms appear as small, gray dead areas that expand to irregularly shaped lesions (blotches). Lesions begin as light green areas that appear to be limited by the leaf veins. Lesions change in color, ending as grayish tan necrotic areas with small, black specks (pycnidia) inside the lesions. Pycnidia exude masses of spores (conidia) upon wetting by rain or dew. Conidia are a source of inoculum and spread the disease within an infected field. Disease is particularly severe in years of higher than average rainfall and can be especially damaging when late spring rains persist after emergence of the flag leaf. The fungus survives between cropping seasons on wheat debris from past crops. The disease is most severe in early-planted wheat because plants are exposed to the pathogen over a longer period of time when weather conditions are frequently favorable to disease development (4, 5).
Growers use resistant cultivars. Later plantings of wheat are less likely to be severely affected. Crop rotation is not effective (4).
Foliar fungicides provide partial disease control. Applications should be made between tillering and heading with the objective being to protect the flag leaf. Depending on the weather conditions, one or more applications may be needed.
· Mancozeb - Label has a rate of 1.6 lb a.i./acre and a 26-day PHI. 24-hour REI. In 2000, 73 lb a.i. were used on 0.2% of California's wheat acreage an average of 1 time at a median application rate of 1.2 lb a.i./acre. (3,7)
· Propiconazole - Label has a rate of 0.1 lb a.i./acre and can be applied until the ligule of the flag leaf emerges. 24-hour REI. In 2000, 76 lb a.i. were used on 1.1% of California's wheat acreage an average of 1 time at a median application rate of 0.11 lb a.i./acre. (3,7)
Rust Diseases of Wheat
Stripe Rust: Puccinia striiformis
Leaf Rust: Puccinia recondita
Stem Rust: Puccinia graminis f. sp. tritici
Three rust diseases, stripe rust, leaf rust and stem rust, occur on wheat. Rust infections reduce plant vigor, root growth and grain filling, resulting in fewer and smaller kernels. Rust diseases have been historically important in wheat cultivation, causing serious epidemics in the past.
Stripe rust is caused by Puccinia striiformis and appears on leaves as yellow orange pustules oriented linearly between vascular bundles. Glumes can be infected. Stripe rust develops earlier in the season than other rusts because the fungus grows at lower temperatures. The stripe rust fungus has caused devastating epidemics on wheat in California. It grows only on living host plants and survives between seasons on volunteer wheat, barley plants, and some wild grasses. Airborne spores cause new infections.
Leaf rust, caused by P. recondita, has reddish orange pustules scattered or clustered on upper leaf surfaces. Pustules turn dark and shiny as teliospores are formed. Leaf rusts appear late in the season. Losses occur in years of below average late spring temperatures and high humidity conditions. The fungus grows only on its living host. Primary inoculum sources are volunteer cereal plants and, because urediospores can be dispersed over great distances by air currents, distant wheat fields.
The stem rust pathogen, P. graminis f. sp. tritici, causes brick red spores are formed to erupt through the surface of host tissues. Pustules can occur on stems, leaves and leaf sheaths. Pustules eventually turn dark and shiny as teliospores are formed. Stem rust does not cause significant losses in California because the commonly grown cultivars are resistant. Primary sources of inoculum are volunteer cereal plants and distant wheat fields. Windblown spores from initial infections initiate secondary cycles (4,5).
Control of rust diseases is achieved through the use of resistant cultivars. Express and RSI 5 are resistant to leaf rust. Stripe and leaf rusts are monitored for early detection of susceptible genotypes and identification of new resistant genotypes (4,5).
To control leaf rust, applications should be made between tillering and heading to protect the flag leaf.
· Propiconazole - See Septoria Tritici Blotch
Barley Yellow Dwarf: Barley yellow dwarf virus
Barley yellow dwarf is an aphid-transmitted virus disease of small grains. Symptoms include leaf discoloration in various shades of yellow, red, or purple and stunting. Tillering is also reduced and maturity is delayed. Severe early infections can kill young plants. Diagnosis is also dependent on the presence of aphid vectors. The virus survives in most common grain aphids and on numerous cereal and grass hosts. Aphids can transmit the virus from an infected host plant to an uninfected host plant during feeding. Epidemics most likely occur during cool, moist seasons that favor grass and cereal growth as well as aphid multiplication and migration. The virus interferes with the growth of infected plants, slowing the development of foliage and roots and sometimes preventing heading or killing the host. (4).
Control is through the use of resistant cultivars and avoidance of very early planting dates.
Chemical Control - Seed Treatment
Loose Smut: Ustilago tritici
Loose smut symptoms usually become apparent at heading. Diseased heads emerge earlier than healthy heads. Olive-black masses of teliospores replace kernels. Smut spores are enclosed in a gray membrane that ruptures to release the airborne spores. Most loose smut pathogens survive from one season to the next as dormant mycelium inside infected seed. U. tritici survives as teliospores on the surface of contaminated seed (4, 5).
Certified smut-free seed is used. Hot water treatments are used to clean seed of smut fungi (4).
· Carboxin/Thiram - Label has a rate of 0.03-0.04 lb a.i.carboxin/100 lb seed and 0.03-0.04 lb a.i. thiram/100 lb seed. 24-hour REI. In 1998, 456 lb a.i. carboxin and 465 lb a.i. thiram were used to treat wheat seed. Only used on wheat grown for seed because of the additional cost for this treatment it is not economical to use on regular wheat production (9).
Covered Smut (Common Bunt or Stinking Smut): Tilletia caries and T. foetida
Diseased plants are stunted and the heads emerge later than normal. Gray spore masses, enclosed in a membrane, replace kernels and persist until grain maturity. During harvest the spore masses burst and spores are spread to healthy grain and the soil. Fungi survive on infested seed or in the soil (4, 5).
Use certified smut-free seed. Hot water treatment can eliminate smut fungi from contaminated seed, but it must be used carefully to avoid reducing seed vitality (4).
Chemical Control - Seed Treatments
Treatment of seed with contact type fungicides will control covered smut because the fungus is on the outside of the seed.
· Carboxin/Thiram - Label has a rate of 0.03-0.04 lb a.i.carboxin/100 lb seed and 0.03-0.04 lb a.i. thiram/100 lb seed. 24-hour REI. In 1998, 456 lb a.i. carboxin and 465 lb a.i. thiram were used to treat wheat seed. Only a minor amount of the wheat acreage uses this treatment to control Covered Smut. (9)
· PCNB - Label has a rate of 0.03 lb a.i./100 lb seed. In 1998, 2,677 lb a.i. were applied to wheat seed. Approximately 66% of the wheat seed is treated with PCNB (9).
Powdery Mildew: Erysiphe graminis f. sp. tritici
Powdery mildew is a major problem in California wheat production. White, cottony patches of fungal growth initially appear on the upper leaf surface of lower leaves. The fungal growth turns a dull gray-brown as spore-forming structures, called cleistothecia, develop. Diseased plants are often low in vigor. The fungus overwinters in cleistothecia that release airborne spores in spring. It can also overwinter as mycelium on volunteer wheat, barley, or oat plants and produce spores that can cause initial infections. Dense stands, high nitrogen fertilization, high relative humidity, and cool temperatures favor disease development (4, 5).
Resistant cultivars are available. Crop rotation, elimination of crop residue, and control of volunteer grains and weed hosts reduce inoculum survival from one season to the next (4).
Foliar fungicides can be used to control disease outbreaks and provide partial disease control.
· Propiconazole - See Septoria Tritici Blotch
Karnal Bunt: Tilletia indica (=Neovossia indica)
Karnal bunt is first visible as blackened areas surrounding the base of the grain; however, the disease is not usually noticed until the grain is threshed and partially smutted kernels are exposed. In most cases, only a few florets per spike are affected and are usually not conspicuous. Karnal bunt only minimally affects grain yield, but since many countries have a zero tolerance for contaminated seed, this disease has regulatory significance. Spores on infected seed and in soil contaminated from the previous crop spread the disease. Wind, splashing water, and insects disperse spores. Plants are most susceptible to infection when spikes emerge from the boot, but infection can occur throughout the flowering period. Diseased kernels may be partially or completely displaced by masses of teliospores. Teliospores have a six-month dormant period before germination and are viable in the soil for up to 45 months (4, 5).
Use of disease-free seed is essential. Currently, no cultivars are immune, but resistant cultivars are being developed (4).
· Carboxin/Thiram - See Karnal Bunt
· PCNB - See Karnal Bunt
Other diseases of wheat that do not usually require chemical treatment include: black point of wheat, common root rot and scab, bacterial blights, ergot, and take-all.
Root knot nematode, Meloidogyne spp.
Lesion nematode, Pratylenchus thornei and P. neglectus
Stem and bulb nematode, Ditylenchus dipsaci
Cereal cyst nematode, Heterodera avenae
Plant parasitic nematodes are microscopic roundworms that feed on plant roots. They survive in soil and plant tissues, and several species may occur in a field. Eight different species of nematodes are known to attack small grains in California. Root knot nematodes are found throughout the state. Their damage is mostly on subsequent rotation crops. The lesion nematode, Pratylenchus thornei, can cause damage to wheat in the Imperial Valley and other warm areas. If grain were planted in spring or summer in Meloidogyne- infected fields the crop could suffer damage.
Root knot nematodes cause cell enlargement and proliferation resulting in swellings or galls on roots. Symptoms caused by lesion nematode, Pratylenchus thornei, are stunting, yellow patches, brown leaf tips, fewer tillers and smaller heads. Stem and bulb nematodes can curl newly emerging leaves into spirals, stunt plants, reduce tillering, inhibit head formation, and sometimes kill plants. The cereal cyst nematode occurs on grasses in California, but it has not been found on small grains. It is potentially damaging to grains; an infestation would produce aboveground symptoms similar to that of root knot and lesion nematodes.
To make management decisions, it is important to know the nematode species present and their population estimates. If a field has a history of nematodes parasitic on wheat, damage can be caused to subsequent crops.
Sanitation is important for managing nematode populations. Washing soil from equipment before moving from infested to noninfested fields can help prevent widespread infestation. Crop rotation with resistant cultivars of oats, Cayuse and Kanota, or to noncereal crops is recommended for fields with M. naasi. Weed hosts should be destroyed during crop rotations. Fall planting is recommended for fields with M. incognita and M. arenaria. A weed-free fallow period reduces most nematode populations. In addition, resistant cultivars of bread wheat are in experimental stages. The use of chemicals to control nematodes is not generally cost-effective (4).
Integrated Weed Management
Weeds compete with wheat for nutrients, water, and light, reducing crop yields and grain quality. An integrated weed management program in small grains combines cultural, mechanical, and chemical weed control practices. A vigorous, competitive crop produced through good cultural practices is the best defense against weed competition. An integrated approach is all inclusive, using good cultural practices and crop rotation along with the appropriate herbicides. Different strategies for weed control are used for grain grown under irrigated and dryland conditions in California. In irrigated fields, the grower has more options to manage weed problems within a rotational system (4).
Early identification of weed pests is important since they are controlled best in the seedling stage. Grain fields are examined when the crop is in the 2- to 3-leaf stage so weeds can be detected easily. Five or more competitive weeds per square yard or one or more large weeds per square yard indicates that the weed population should be removed by an herbicide application to avoid an economic yield loss (4).
Special Weed Problems
Annual Broadleaf Weeds
In fall-planted grain, important broadleaf weeds are winter radish, fiddleneck, wild mustard, black mustard, London rocket, shepherd's-purse, and spiny sowthistle. In spring-planted grain, summer annuals such as redroot pigweed, common lambsquarter, kochia, Russian thistle, and common sunflower can be economically important. Wild beet is a problem in the Imperial Valley. Smartweed is a major problem in Delta areas with high water tables (4).
Annual Grass Weeds
Grassy weeds in wheat are generally winter annuals. Wild oat, Italian ryegrass, ripgut brome, foxtail, wild barley, and hood canarygrass are the major grass weeds in small grains grown in California. Ripgut brome, Italian ryegrass, and hood canarygrass are problems in central coast dryland areas. Other problem grass weeds include littleseed canarygrass, rabbitfoot polypogon, and jointed goatgrass. There are no chemicals registered for goatgrass control in wheat, management of this weed is either when the field is fallow or planted to a rotation crop. Grassy weeds are normally a greater problem in dryland production than on irrigated land, because grains are not grown in rotation with broadleaf crops in these areas (4).
Field bindweed is the most widespread and destructive perennial broadleaf weed in California. Field bindweed can be suppressed with 2, 4-D during the growing season, or with glyphosate or dicamba after harvest. Johnsongrass is a problem, especially in the Sacramento/San Joaquin Delta and the Central and Imperial Valley. Johnsongrass growth just before and after harvest can be controlled by glyphosate (Roundup). Repeated summer tillage helps reduce johnsongrass competition in the next crop.
Non-Chemical Weed Management Practices
Cultural practices including, keeping fence lines, ditches, and wasteland areas free of weeds to reduce sources of infestation, are important practices in wheat production. Thoroughly cleaning combines and tillage equipment before entering or leaving a field.
Seed certified can offer potential for higher yield, increased germination, and reduced risk of introducing a new weed species. Crop rotation is of utmost importance for control of grassy weeds. Important rotational crops include cotton, corn, alfalfa, potato, sugarbeet, dry beans, tomato, and safflower. Crop/fallow rotation is also beneficial in managing weeds.
In arid regions, cereal growers often pre-irrigate or wait for the first rain to germinate weed seeds and remove them by tilling before planting or by applying a postemergent herbicide such as glyphosate or paraquat.
Adequate drainage, good tillage practices, high seeding rates, and adequate fertilizer are additional measures that may help control weed pests.
Since cultivation is not possible after grain is planted, producers must rely on herbicides and good agronomic practices for effective control. Uncontrolled weeds delay maturing grains and create harvest problems. A mature grain field contaminated with immature weeds may be harvested in one of two ways: (1) the crop may be swathed or (2) where permitted, formulations of 2, 4-D and glyphosate (Roundup) that are registered as preharvest aids can be applied to mature grain to kill and dry out weeds (4).
Postemergence herbicides are applied to the crop, usually at the 2- to 3-leaf and tillered stages. Choice will depend on the weed spectrum present, location of the field in relation to susceptible crops, and the crop that follow small grains in the rotation. Depending on weeds present, one or two herbicide applications or combinations may be required. Application must be properly timed for maximum weed control and avoidance of crop injury. Combinations of two broadleaf herbicides are used under certain conditions. State and County regulations forbid the use of dicamba or the phenoxy herbicides (2, 4-D and MCPA) at certain times during the growing season; adjacent crops, such as grapes or cotton, dictate the use of a nonphenoxy herbicide to reduce the possibility of drift and injury. The cutoff date for 2, 4-D, MCPA, and dicamba is as early as March 15 in grape growing areas. In other areas, it may extend as late as October 15. There are no cutoff dates for phenoxy herbicides in the Sacramento Valley (4).
· Dicamba - Label has a rate of 0.25-2 lb a.i./acre and a 24-hour REI. In 2000, 6,977 lb a.i. were used on 13% of California's wheat acreage an average of 1 time at a median application rate of 0.15 lb a.i./acre. (3,7)
· Paraquat - Label has a rate of 0.47 - 0.93 lb a.i./acre and a 12-hour REI. In 2000, 747 lb a.i. were used on 0.5% of California's wheat acreage an average of 1 time at a median application rate of 0.26 lb a.i./acre. (3,7)
· Glyphosate - Label has a rate of 1.25-2.0 lb a.i./acre and a 12-hour REI. In 2000, 14,775 lb a.i. were used on 4.0% of California's wheat acreage an average of 1 time at a median application rate of 1.0 lb a.i./acre. (3,7)
· 2, 4-D - Label has a rate of 0.32-0.96 lb a.i./acre and a 48-hour REI. In 2000, 110,065 lb a.i. were used on 31% of California's wheat acreage an average of 1 time at a median application rate of 0.85 lb a.i./acre. (3,7)
Pre-plant or Pre-emergence - Under no-till conditions, the first flush of weeds can be controlled before planting depending on weeds present
· Paraquat - See Fallow period for specific label and usage information.
· Glyphosate - See Fallow period for specific label and usage information.
· Difenzoquat - Widely used for wild oat control. Label has a rate of 0.63-1 lb a.i./acre and a 48-hour REI. In 2000, 11,789 lb a.i. were used on 2.1% of California's wheat acreage an average of 1 time at a median application rate of 1.0 lb a.i./acre. (3,7)
· Dicamba -See Fallow period.
· Bromoxynil - Used to control annual weeds, especially coast fiddleneck. Label has a rate of 0.25-0.38 lb a.i./acre and a 12-hour REI. In 2000, 37,143 lb a.i. were used on 19.5% of California's wheat acreage an average of 1 time at a median application rate of 0.55 lb a.i./acre. (3,7)
· Chlorsulfuron - Controls a wide spectrum of broadleaf weeds, including mustards, fiddleneck, and chickweed. Label has a rate of 0.00031-0.00064 lb a.i./acre and a 4-hour REI. In 2000, 93 lb a.i. was used on 3.2% of California's wheat acreage an average of 1 time. (3,7)
· MCPA- Used to control annuals and provides partial control of field bindweed. Label has a rate of 0.25-1.0 lb a.i./acre and a 48-hour REI. In 2000, 114,526 lb a.i. was used on 42% of California's wheat acreage an average of 1 time. (3,7)
· 2, 4-D - See Fallow period.
· Diclofop-methyl - Used for specific grass control in wheat in certain counties. Label has a rate of 0.5-1 lb a.i./acre and a 24-hour REI. 77-day PHI. In 2000, 21,154 lb a.i. were used on 6.5% of California's wheat acreage an average of 1 time at a median application rate of 0.96 lb a.i./acre. (3,7)
Storage, Facility and Export Treatments
It is important for grain storage bins to keep grain dry while excluding rodents, insects, and birds. Thus, they need to allow for forced aeration while having the ability to be airtight should fumigation be necessary. Insect infestations can be avoided by good sanitation methods. Sweeping the grain bins clean, destroying all the sweepings and cleaning the harvest equipment of residual grains are important. Sometimes a gaseous fumigation with methyl bromide, chloropicrin or aluminum phosphide may be necessary. Bins should be monitored periodically for insects and molds (8).
Storage and Facility Treatments
· Aluminum phosphide - In 1998, 1,817 lb a.i. were applied to stored grain. This is a use applied directly to stored grain. (9)
· Malathion - Label has a rate of 5 lb a.i./25 gallons water. 12-hour REI. Malathion is applied to the storage facility prior to the crop being stored. Therefore it is reported as a structural application. Specific information concerning the stored agricultural commodity is not available. (9)
Vapona - Dichlorvos (DDVP) - Was used in 1996, but no reported use in 1997 or 1998. Dichlorvos is applied as a fumigant to the storage facility. Therefore there are different reporting requirements that may not be crop specific. Awaiting a follow-up from Mike Adams. (9)
1) California Wheat Commission. http://www.californiawheat.org/variety_survey.html
2) Summary of County Agricultural Commissioner's Report. CASS 2000
3) CDMS - Label references
4) University of California Integrated Pest Management Guidelines: Small Grains. June 1999.
5) Compendium of Wheat Diseases. 1997. M.V. Wiese, Ed. American Phytopathological Society Press. St. Paul, Minnesota.
6) Crop Protection Reference. 1999. Fifteenth Edition. C and P Press. New York.
7) Department of Pesticide Regulation. 2000Annual Pesticide Use Reports.
8) Cook, R.J. and Veseth, R.J. Wheat Health Management.1991. American Phytopathological Society Press. St. Paul, Minnesota.
9) Personal communication February 29, 2000 with Mike Adams, Adam's Trucking, Arbuckle, California.
10) California Agricultural Statistics. http://www.cdfa.ca.gov
University of California
One Shields Avenue
Davis, CA 95616
|Common Chemical Name||
% Ac Treated
|Base Ac Treated||Total Lbs AI||
% Ac Treated
|Base Ac Treated||Total Lbs AI|
|Dicamba, Dimethylamine Salt||14%||72,335||10,304||13%||44,711||6,239|
|Difenzoquate Methyl Sulfate||3%||13,162||13,248||2%||5,357||5,434|