Prepared: March 2005
|
|
|
*In 2002, Virginia Agricultural Statistics Service discontinued data for cantaloupes.
Production Regions
The largest amount of cantaloupe acreage is located in the Northern Neck county, Westmoreland, and Hanover county in the Richmond area. New Kent county and Halifax county also produce a large amount of acreage in Virginia.
The melon commercially referred to as "cantaloupe" is actually muskmelon (Cucumis melo, Reticulatus group). The Reticulatus group includes all melons with netting, and has thick, orange flesh, a musky fragrance, and a stem that disconnects from the fruit at full maturity. The "true" cantaloupe (C. melo, Cantalupensis group) is grown in Europe and is a small fruit with hard, scaly, or warty skin. Muskmelons are warm-season vining crops, generally requiring 80-120 days of warm conditions from seed to maturity. Best melon quality is obtained in areas with high temperatures, high light, minimal rainfall, and relatively low humidity during the growing season. Fruit quality depends upon high sugar content (10%-12% sugar at maturity). Melons can withstand short periods of drought stress, but fruit quality is adversely affected by excessive rainfall or over-irrigation that serves to dilute the sugar concentration within the fruit.
Varieties* recommended for growing in Virginia include: Superstar, Aphrodite, Eclipse, and Athena. Several specialty varieties of the Inodorus group, with green or white flesh, are also available to Virginia growers: Earli-Dew, Marygold, and Tennerife. Variety selection depends on several factors such as market acceptability, yield, and horticultural characteristics. The disease pressure from Fusarium wilt is severe in most eastern growing areas, including Virginia. Only cultivars with Fusarium resistance are recommended.
*Varieties are listed by maturity, earliest first.
Muskmelons are andromonoecious (both perfect and male flowers on the same plant with the male flowers appearing first). Generally, three to five melons are set per plant. Not all of these will be of marketable size or quality.
Planting dates vary from May 1 in southern regions to June 5 in northern areas. Container-grown plants should be transplanted through plastic mulch when daily temperatures have reached 60°F. Temperatures below 45°F can stunt plant growth. Early plantings should be protected from winds with hot caps, tents, row covers, or rye strips. The recommended spacing for cantaloupes is 5-6 ft. between rows with 2-3 ft. between plants in the row.
When mulching, lay clear plastic mulch before field plantings. This conserves moisture, increases soil temperature, and increases early and total yield. Fumigated soil also helps control weeds and soilborne disease. Plastic and fumigant metam-sodium (Vapam HL) should be applied on well-prepared planting beds 30 days before field planting. Plastic should be 4 ft. wide and laid on 5 or 6 ft. centers immediately over the fumigated soil. The soil must be moist when laying the plastic. Fumigation alone may not provide satisfactory weed control under clear plastic. Herbicides labeled and recommended for use on cantaloupes may not provide satisfactory weed control when used under clear plastic mulch on nonfumigated soil. Black plastic or paper can be used without a herbicide. Fertilizer must be applied during bed preparation. At least 50% of its nitrogen should be in nitrate form. If there is a history of soilborne diseases in the field, fumigation will be necessary. Consult your county agent for the latest recommendations.
Melons cross-pollinate. Therefore, honeybees are important for pollination and proper fruit set. Populations of pollinating insects may be harmed by insecticides applied to flowers or weeds in bloom. Apply insecticides only in the evening hours, or wait until bloom is completed before application.
Although several alternatives are possible, the basic production system consists of direct seeding or transplanting of melons into worked ground, herbicide application, then irrigation, pest control, and cultivation, followed by harvest.
Harvest dates in Virginia typically range from the middle of July through August. Harvesting usually begins 68 days after planting or 33-35 days after full bloom, depending upon cultivar and environment. The harvest period begins when fruits reach full slip; i.e., when the stem separates easily at the point of attachment. This period lasts usually one month with three pickings per week, until the plants cease to produce marketable fruits. The stage at which melons are picked depends upon the final market. Those remaining on the vine the longest tend to have the greatest accumulation of sugars but are softer and less transportable. The harvest of melons begins in the early morning, when fruit temperatures are cooler. Generally, the fruit harvested from the first cycle of fruit set has the highest quality. Fruit is selected for harvest according to its stage of maturity and distance to market. Ripeness of fruit is determined by physical properties or with instruments. Well-developed, raised netting; smooth, rounded stem scars; and characteristic aroma are the predominant qualities of full ripeness. Melons to be shipped are often picked when the stem starts to depart from the fruit (half-slip as apposed to full slip when mature). Melons are usually harvested by hand. Mechanization is not practical since fruit maturity is highly variable.
Worker Activities
During the growing season, worker activities in the field could include transplanting (May-June), cultivating, irrigating, scouting, spraying, occasional hand weeding, and harvesting (July-August). Strictly following re-entry intervals (REIs) should minimize any risk of exposure to pesticides during these activities. If workers are required to go back in the field before the proper time limit has expired then personal protective equipment (PPE) is worn. Activities that bring workers in direct contact with the plants during the growing season are generally limited to harvest time because the fruit is hand-picked.
Special Use Labels
Section 18 Emergency Use Exemption and Special Local Need 24(c) labels supplement the chemical tools available to producers for pest control. Once the problem or gap in pest control has been identified, specialists submit the proper documentation for the Emergency Use/Special Local Need label. Thus far, Extension specialists have been successful in obtaining these labels. Special Local Need (SLN) labels in Virginia are granted by the Virginia Department of Agriculture and Consumer Services (VDACS) and are usually only valid for limited time intervals. Section 18 Emergency Use labels are evaluated and granted by the Environmental Protection Agency (EPA) and can be renewed annually. Without these temporary use labels, pest control in vegetable crops may be extremely difficult for producers.
Control recommendations found below were modified from information presented in the 2004 Commercial Vegetable Production Recommendations-Virginia6, unless otherwise noted.
INSECTS7
In general, cucumber beetles are the most economically important insect pests of cantaloupe in Virginia. Other important pests include: spider mites, which can be particularly devastating in hot, dry years, and aphids, especially after cool springs. Other minor pests include: seedcorn maggots, serpentine leafminers, pickleworms, cabbage loopers, and cutworms.
Aphids
Green Peach Aphid, Myzus
persicae
Melon Aphid, Aphis gossypii
Both the green peach aphid and the melon aphid are pests on cantaloupe. However, the latter is the primary species infesting cantaloupes in Virginia. In general, aphids feed on plant sap, which may reduce plant vigor, size, and yield. Also, as they feed on the underside of the leaves, aphids excrete honeydew. This, in turn, leads to the growth of black, sooty mold, which may block out sunlight and thus reduce plant yield. In addition, aphids can vector certain plant viruses. In particular, the melon aphid is instrumental in transmitting the cucumber mosaic virus, which can be devastating to cantaloupe production.
Monitoring: If a systemic insecticide such as imidacloprid or thiamethoxam is not applied at planting, then aphid scouting is recommended. Scouting for melon aphids should begin as soon as plants form runners. Examine two runners at five sites in the field. Record the number of runners with live aphids present. Treatment is recommended if >20% of runners have aphids.
Chemical Control: Systemic insecticides applied at planting are the best method of control. If foliar sprays are used, then thorough spray coverage beneath leaves is important. See the Chemical Insect Control section for recommendations.
Biological Control: A number of natural enemies such as lady beetles (adults and larvae), lacewing larvae, syrphid larvae, parasitic wasps, and fungal pathogens will reduce aphid populations. Natural enemies will often keep aphid populations below damaging numbers and, therefore, should be considered before making an insecticide application. However, if the spread of the virus is of concern, chemical treatment will be necessary.
Cultural Control: Plant disease-free certified seed. Avoid planting in fields immediately downwind of a barrier such as hedgerows or woodlots, which reduce wind velocity and increase the number of dispersing aphids falling into fields. These barriers can also cause over fertilization with nitrogen, which results in lush growth attractive to aphids.
Cabbage Looper, Trichoplusia ni
Cabbage loopers may be identified by their pale green color, thin white stripes down the back and sides, and by their doubling-up or looping as they move. These insects feed on the underside of leaves, producing ragged holes of various sizes. Feeding begins in late July or early August and usually continues through harvest. Healthy plants can usually sustain feeding injury unless populations become exceedingly large. Several generations can occur during a year. Loopers are not usually serious pests of cantaloupes in Virginia.
Monitoring: Check leaf-feeding levels in the field at least weekly. Healthy and older plants can usually withstand moderate defoliation before economic yield loss to the fruit occurs. Moth activity can be monitored at blacklight traps.
Chemical Control: See the Chemical Insect Control section for recommendations.
Biological Control: There are several parasitic wasps and predators that attack the cabbage looper. Also, a nuclear polyhedrosis virus (NPV) can substantially reduce population levels of larvae, especially after a rainy period.
Cultural Control: No current recommendations for commercial production.
Cucumber Beetles (Rindworms)
Spotted Cucumber
Beetle, Diabrotica undecimpunctata howardi
Striped Cucumber
Beetle, Acalymma vittata
Both the spotted and striped cucumber beetles (adults and larvae) may severely reduce cantaloupe productivity. These pests are the number one concern of growers in Virginia. Adults overwinter in wooded areas and fields, then migrate in the spring to cucurbit crops. Adults mass on plants and feed voraciously on the foliage and stems, often causing girdling, which will greatly reduce plant stands. Adults will also feed on the blossoms of developing plants, causing later scarring of the fruit8. Cucumber beetles transmit bacterial wilt, and most varieties of cantaloupes are highly susceptible to this disease.
In addition to the damage adult cucumber beetles cause, the larval stage, otherwise known as a rindworm, feeds directly on the roots and on cantaloupes. This feeding typically occurs at the bottom of the fruit where the melons contact the soil, rendering them commercially unmarketable. Management of adults (beetles) is necessary to reduce the number of rindworms. Direct control of rindworms can be difficult.
Monitoring: Begin scouting for beetles following transplant or as soon as the plants emerge. Scout twice a week, especially when plants have less than five leaves. At each of the five sites, scout five plants for beetles. Treat when an average of two beetles/plant are found.
Chemical Control: Foliar insecticides should be used to control adult beetles before they feed extensively on the cotyledons and first true leaves. Begin spraying shortly after plant emergence and repeat applications at weekly intervals if new beetles continue to invade fields. Treatments may be required until vines begin to run. To provide additional pest control, a Special Local Need 24(c) label has been approved in Virginia for the use of carbofuran (Furadan 4F) at planting. See the Chemical Insect Control section for more information.
Biological Control: No current recommendations for commercial production.
Cultural Control: Always cultivate the soil thoroughly before planting. The use of plastic or straw as bedding for the developing melons may deter rindworm feeding. In the fall, eliminating surrounding weeds will reduce the overwintering sites for the beetles.
Cutworms
Black Cutworm, Agrotis
ipsilon
Variegated Cutworm, Peridroma
saucia
Granulate Cutworm, Feltia subterranea
Cutworms are sporadic pests of many crops. Several species of cutworm may be found in Virginia. Most are night feeders that hide under plant and soil debris common in weedy or minimum-tillage fields. Another distinguishing quality is their habit of rolling into a tight C-shape if disturbed. Newly hatched cutworm larvae feed on young plants at the soil line, often severing the stems. Later generations of cutworms feed on developing melons and in severe cases may tunnel completely through the fruit. This greatly diminishes marketability.
Monitoring: Even if a preplant broadcast insecticide treatment is used, fields should be scouted for cutworm damage within a week of planting or plant emergence. Cutworms are not typically seen in the open during the day; however, digging in the soil around injured plants may reveal them. If cutworms are actively cutting plants, a postplant contact treatment may be used.
Chemical Control: See the Chemical Insect Control section for recommendations.
Biological Control: Cutworms are attacked by many ground-dwelling insect predators, especially carabid beetles. Also, pathogens such as Beauveria bassiana and entomopathogenic nematodes often will infect larvae.
Cultural Control: Proper tillage will help eliminate some species of cutworms that may move off of cover crops.
Leafminers
Serpentine Leafminer,
Liriomyza brassicae
Leafminers injure leaves primarily by mining the leaves, which results in the destruction of leaf mesophyll tissue. As the larvae hatch from eggs deposited within the leaf tissue, they create slender, winding white tunnels in their search for food. Mature larvae emerge from inside the leaf and drop to the soil, where they pupate in soil crevices or, in rare cases, the leaf. Leaf mining depresses the level of photosynthesis and may cause leaf droppage. Fewer leaves in the canopy can result in sun scalding of fruit. Many generations occur annually in Virginia, but the first is usually the most damaging.
Monitoring: The economic consequences of leaf mining are not well understood; thus, adequate scouting procedures have not been developed.
Chemical Control: See the Chemical Insect Control section for recommendations.
Biological Control: Parasitoids often provide excellent suppression of leafminers if broad-spectrum insecticides are not applied to the crop.
Cultural Control: No current recommendations for commercial production.
Pickleworm, Diaphania
nitidalis
Melonworm, Diaphania hyalinata
The melonworm is generally a foliage feeder (unlike the pickleworm, which attacks the developing leaf and flower buds) but also damages the vines and fruit. The adults overwinter in the warmer southern regions and begin to migrate north when temperatures warm. Females deposit eggs on the leaf surface. The larvae emerge several days later, feeding on the flowers, vines, and fruit for up to two weeks. Although several generations can occur during a year, pickleworm and melonworm are rarely serious pests of cantaloupes in Virginia.
Monitoring: As soon as pickleworms or their damage appears, begin insecticide treatments.
Chemical Control: Make one treatment before fruit set, and then treat weekly. See the Chemical Insect Control section for recommendations.
Biological Control: No current recommendations for commercial production.
Cultural Control: After harvest, remove all debris from the field, destroy vines and unused fruit, and control adjoining weeds. Also, plowing early in the fall will bury the pupae. In the spring, planting early will help the crop establish itself, thus preventing major damage.
Seedcorn Maggot, Hylemya platura
The seedcorn maggot is most noted for its damage to seeds or seedlings in bedding trays and early-planted fields, especially during cool, wet growing seasons. Adults emerge in early spring to lay their eggs, preferably in moist, organically rich soils, such as freshly plowed fields or greenhouse flats. Larvae or maggots hatch from the eggs and bore into seeds, cotyledons, or rotting crop debris. The maggots feed for one to three weeks before tunneling into the soil, where they pupate for about one to four weeks or for the duration of the winter. Multiple generations occur annually in Virginia.
Monitoring: Once seedcorn maggot damage has been observed, treatments are ineffective. Therefore, management options must be applied to high-risk fields before planting. High-risk fields can be defined as those having previous seedcorn maggot infestations or soils high in organic matter.
Chemical Control: Control is best achieved by using insecticide seed treatments such as chlorpyrifos (Lorsban SL) or diazinon (Agrox D-L Plus, Diazinon 50W, Germate Plus, Kernel Guard, or KickStart). The use of imidacloprid (Admire 2F) at planting will also reduce seedcorn maggot populations. Seed treatments containing malathion or lindane or seed commercially treated at low rates for seed storage will not control seed maggots. Do NOT use treated seed for food or feed.
Biological Control: No current recommendations for commercial production.
Cultural Control: Several management practices can reduce the potential for damage resulting from seedcorn maggot infestations. These include plowing weeds or cover crops at least two weeks before planting or transplanting, avoiding overfertilization with manure, and completely plowing under crop debris immediately after harvest to remove plant remnants.
Squash Bug, Anasa tristis
Squash bugs destroy plant tissue by secreting a highly toxic saliva into the plant, sucking out the sap from the leaves and stems, and depleting nutrients from the plant. This feeding causes leaves to wilt and dry out. They eventually turn black and fall off the vine. Adults can be seen feeding on the main stems. Nymphs are more likely found feeding on the underside of the leaves. The adults are brown or black, flat-backed, and 1/2 to 3/4 inch long. Nymphs have gray-green bodies with red or black legs. Adults overwinter in garden debris and emerge the following spring to lay eggs. When the plants develop runners, elliptical brown eggs are laid in groups on the underside of the leaves.
Monitoring: All stages of plants may be attacked by squash bugs. If wilting is observed in a field, check the underside of leaves for egg masses, nymphs, or adults. Adults are often cryptic and hide in plant debris on the ground. A treatment is recommended if >1 egg mass or aggregation of nymphs is found per plant.
Chemical Control: Begin treatments shortly after vines run. Treat every seven to ten days or as needed. If insecticides are to be applied when blossoms are present, use products with little residual activity and apply them late in the day, when honeybee activity is minimal. See the Chemical Insect Control section for more information.
Biological Control: No current recommendations for commercial production.
Cultural Control: After harvest is complete, deep tillage or removal of crop residue will help to delay and/or reduce infestation the next spring.
Squash Vine Borer, Melittia cucurbitae
The squash vine borer injures plants by tunneling through their stems. This interferes with nutrient transfer in the plant, eventually causing the plant to wilt. Borer feeding weakens plants, providing the opportunity for secondary infections. The larvae have a brown head, white body, and are rarely found outside of the vine. The adults may be mistaken for a wasp. The body is orange and black, often in a ringed pattern surrounding the abdomen. The squash vine borer overwinters as a pupa, and adults emerge in the spring to lay eggs. It is usually not a significant pest in cantaloupes in Virginia.
Monitoring: There are no practical methods for direct sampling of adults or eggs in the field. When plants are checked for general vigor and other factors, borer damage may be detected. No regular monitoring is done specifically for this pest, however.
Chemical Control: When vines begin to run, apply recommended insecticide to bases of plants four times at seven-day intervals. See the Chemical Insect Control section for more information.
Biological Control: No current recommendations for commercial production.
Cultural Control: Proper cultural control may kill many overwintering pupae, reducing the following year's population. Soil should be disked after harvest and then plowed the following spring. Destroying vines after harvest prevents borers still in the larval stage from completing their development.
Thrips, Thrips tabaci
Thrips are small, slender insects pale yellow to dark brown. Its two pairs of wings are narrow and fringed with long hairs. The nymphs are wingless and may be green or yellow with red eyes. Both nymphs and adults feed in the plants, causing silvering and sometimes deformation of the leaves; edges of the leaves tend to curl upward.
Monitoring: Yellow sticky cards can be used to monitor the incidence or timing of thrips entering fields; however, there are no current recommendations for commercial production.
Chemical Control: See the Chemical Insect Control section for more information.
Biological Control: No current recommendations for commercial production.
Cultural Control: Destruction of crop residues after harvest eliminates overwintering sites.
Two-Spotted Spider Mites, Tetranychus urticae
Spider mites can be a very serious pest of cantaloupes. Typically, they feed on the undersides of leaves, often causing them to turn brown and fall off. Severe infestations, especially of smaller, stressed plants, may cause death. Mite problems are often associated with hot, dry weather and as such have become a regular problem in Virginia over the past several years.
Monitoring: Scout fields, especially areas that border roadsides or weedy edges or areas of the field that are sandy. Examine both the upper and lower sides of five crown leaves from five to ten locations and look for white stippling. Also note the condition of terminal leaves. Treatment should be made when 10% -15% of the crown leaves are infested early in the season, or when 50% of the terminal leaves are infested later in the season.
Chemical Control: Spot treatment of "hot spots" and areas along the edges of fields is recommended to control mite populations when problems are first noticed. Begin treatment when 10% -15% of the crown leaves are infested early in the season, or when 50% of the terminal leaves are infested later in the season. Use of dimethoate for leafminer control will reduce mite populations. The products Agri-Mek, Capture, Danitol, and Kelthane are excellent miticides. Continuous use of carbofuran (Furadan) and carbaryl (Sevin) or pyrethroids without miticidal activity for other pests may cause mite outbreaks. See the Chemical Insect Control section for more information.
Biological Control: Natural predators and diseases of mites are present in fields, but rarely at levels high enough for adequate control during outbreaks.
Cultural Control: If possible, avoid mowing field margins and grassy areas until after midsummer since this forces mites into the crop.
Whiteflies, Bemisia argentifolii
Whiteflies usually occur in groups on the underside of leaves. They derive their name from the mealy white wax covering the adult's wings and body. Adults are tiny insects with yellowish bodies and whitish wings. The nymphal stages are wingless. Whiteflies suck phloem sap. Large populations can cause leaves to turn yellow, appear dry, or fall off plants. Like aphids, whiteflies excrete honeydew, so leaves may be sticky or covered with black sooty mold. Feeding can cause plant distortion, discoloration, or silvering of leaves. Generally, plant losses do not occur unless there is a significant population of whitefly nymphs.
Monitoring: Sticky traps can be used to monitor populations.
Chemical Control: See the Chemical Insect Control section for more information.
Biological Control: Many predators, parasitoids, and fungal pathogens attack whiteflies, and can usually keep populations below damaging levels. Use of broad-spectrum insecticides often eliminates natural enemy populations, however.
Cultural Control: Proper cultural controls are vitally important in managing whiteflies. Since they move from crop to crop, prompt tillage of land and destruction of crop residues can help reduce whitefly densities. Proper weed management is also recommended since many weed species can harbor whitefly populations.
Chemical Insect Control
The list below contains all of the products available to producers for insect control in cantaloupe along with the recommended application rates. Always consult the label before making an application. PHI = Pre-Harvest Interval. REI = Re-Entry Interval.
Control recommendations found below were modified from information presented in the 2004 Commercial Vegetable Production Recommendations-Virginia.9
DISEASES
Disease in cantaloupe can slow down development and injury the leaves and fruit, greatly reducing the yield and making the crop less profitable. Each of the diseases listed below occurs within Virginia and depends primarily on weather conditions but also on a number of other factors. These include site location, seed quality, and effective management procedures. Good sanitation and management practices are key to a successful disease control program. Bacterial wilt, gummy stem blight, and powdery mildew are the most frequently occurring diseases in Virginia.
Alternaria Leaf Blight, Alternaria cucumerina
Alternaria leaf blight causes damage by defoliating the vines and reducing fruit yield, size, and quality. This disease usually attacks the oldest leaves or crown leaves, producing round, water-soaked lesions or transparent spots near the center of the hill. Warm, humid weather causes the lesions to blacken and to grow rapidly, eventually spreading to the younger leaves on the tip of the vine. On the fruit, circular sunken spots develop that later become covered with a dark olive-green to black mold.
Monitoring: Monitoring your crop on a regular basis for disease will help you apply pesticides when needed.
Chemical Control: Begin spraying when vines begin to run. Alternate chlorothalonil with Pristine, Cabrio plus chlorothalonil, or Quadris (Amistar) plus chlorothalonil every seven days. This is especially important to delay the development of resistant strains of the pathogen to strobilurin fungicides. See the Chemical Disease Control section for more information.
Biological Control: No commercially effective controls are available.
Cultural Control: Using resistant varieties whenever possible and following a proper management routine will help reduce the risk of infection. Make sure you rotate cucurbits with other vegetables for three or four years. After harvest, plow under or burn any crop debris left in the field.
Bacterial Wilt, Erwinia tracheiphila
Initially, the foliage becomes dull green, and individual leaves droop in early stages of infection. Eventually, leaves and entire branches lose turgor, wilt, and die. Bacterial wilt is carried by the striped and spotted cucumber beetles. The bacteria live in the digestive tract of the beetle and invade the plant through the wounds caused by the beetles. The bacteria multiply within the xylem tissue of the plant until water movement is obstructed. Entire plants may collapse and die within a few days.
Monitoring: Weekly scouting for cucumber beetles should begin following transplant of plants or as soon as the plants emerge. When an average of two beetles per plant is found, a treatment plan should be started. A good diagnostic field test is to cut the plant near the crown and squeeze sap from the newly cut stem. Heavily infected plants will ooze a milky sap from the cut stem. Regardless of whether you see the milky sap, touch a clean knife to the cut surface and draw the surfaces apart. If you see threads stringing from the stem and knife blade, then the plant has bacterial wilt.
Chemical Control: Bacterial wilt control is directly related to control of cucumber beetles. Soil-applied insecticides and repeated applications of foliar contact insecticides are necessary for adequate disease control. See the Chemical Insect Control section for more information.
Biological Control: No commercially effective controls are available.
Cultural Control: Control is aimed at prevention of the infection by the beetles. Since cucumber beetles overwinter as adults, early control measures are necessary. Young plants can be protected by row covers, cones, or other types of mechanical barriers. Infected plants should be pulled up and destroyed. There are no varieties available to growers with resistance to bacterial wilt.
Damping-Off, Fusarium oxysporumi and Pythium spp.
These soilborne diseases cause young seedlings to wilt and die, or to not emerge at all. Generally, these diseases occur during wet soil conditions. Pythiummore commonly causes damping-off in cucurbits, but Fusarium occasionally does.
Monitoring: Monitoring your crop just after transplant will enable replanting for the current crop and reveal fields that need treatment in future crops.
Chemical Control: To protect against damping-off pathogens, seeds are usually treated with broad-spectrum contact fungicides. Ridomil Gold 4E or Ultra Flourish 2E can be used for Pythium disease control. See the Chemical Disease Control section for more information.
Biological Control: No commercially effective controls are available.
Cultural Control: Use of resistant cultivars can help to prevent damping-off caused by Fusarium. Practices that promote water drainage such as planting on raised beds can help to reduce Pythium damping-off.
Downy Mildew, Pseudoperonospora cubensis
Downy mildew is most prevalent during extended periods of cool, moist weather conditions. Symptoms appear as irregular yellowish to brown spots on the upper leaf surface, eventually becoming more distinct on both sides of the leaves. On wet mornings, the underside of the leaves may exhibit a brown to gray fungal growth. These spots grow rapidly and turn black, eventually causing the leaf to wilt and die. This can lead to major foliage loss in the crop and sunscald to fruit.
Monitoring: Scout fields for disease incidence beginning in mid-July, even though generally this disease does not occur until mid-August. Downy mildew comes to Virginia from the South. Check the website www.ces.ncsu.edu/depts/pp/cucurbit/ to see if the disease has been detected in your region.
Chemical Control: Begin sprays when vines run or if disease occurrence is predicted for the region. Use chlorothalonil or mancozeb every seven days. Other effective fungicides, such as mefenoxam + chlorothalonil, copper or mancozeb, Acrobat + mancozeb, or Pristine or Tanos + chlorothalonil, should be applied every other spray. See the Chemical Disease Control section for more information.
Biological Control: No commercially effective controls are available.
Cultural Control: Crop rotation has little effect on prevention of downy mildew. It is important to promote healthy, vigorous growth and a good nutritional program in the crop, as plants under nutritional stress are more susceptible to the disease. Also, avoid overhead irrigation.
Fusarium Wilt, Fusarium oxysporum f. sp. melonis
This fungus attacks cantaloupe plants at any growth stage. If infection is already present, seedlings will start to wilt and will die soon after emergence. Leaves close to the crown of the plant usually wilt first. Yellowing of the crown leaves may also occur. The most characteristic symptom is that the large roots and internal tissues near the ground are stained a brown or brick red color. High temperatures can make the infestation more severe, along with nematodes, which can enter as a secondary pathogen.
Monitoring: Monitoring your crop on a regular basis will help you to identify fields where this disease may be a problem. Crop rotation and resistant cultivars would be necessary in these fields in future crops.
Chemical Control: See the Chemical Disease Control section for more information.
Biological Control: No commercially effective controls are available.
Cultural Control: Using a long rotation with noncucurbit crops for at least five years will help to slowly reduce Fusarium populations in soil. Whenever possible use resistant varieties; however, if pathogen populations are high, even resistant cultivars can wilt and die.
Gummy Stem Blight, Didymella bryoniae
This disease primarily occurs in late summer and can attack all parts of the plant except the roots. It also can occur at any growth stage, from seedlings to mature plants. The first symptoms appear as reddish brown lesions on the main stems and dark circular lesions on the leaf margins. During constant rain or high humidity, these lesions can spread very quickly and cause curling, shriveling, and even leaf death.
Monitoring: Monitoring your crop on a regular basis for disease will help you apply pesticides when needed.
Chemical Control: Begin sprays when vines begin to run. Alternate chlorothalonil with Amistar, Pristine, or Cabrio + Bravo or mancozeb every seven days. Tank-mix Amistar, Pristine, or Cabrio with Bravo or mancozeb to delay onset of resistance. Do not apply Amistar, Pristine, or Cabrio more than four times per season. See the Chemical Disease Control section for more information.
Biological Control: No commercially effective controls are available.
Cultural Control: As there are no resistant varieties available, crop rotation with noncucurbits for three to four years is very important. To reduce survival of the fungus, plow any crop refuse deeply into the ground right after harvest is complete.
Manganese Toxicity
Excess soil acidity allows elemental manganese that is normally bound to soil particles to be released and taken up in the plant in very high concentrations. Losses to manganese toxicity can be severe. Symptoms of manganese toxicity usually appear shortly before harvest. Crown leaves of plants with heavy fruit loads assume an unhealthy, pale green cast. Close inspection of the leaves reveals tiny lesions surrounded by yellow halos. This characteristic is best observed by viewing the leaf in bright sunlight. The lesions mature, coalesce, and often turn brown. The combination of symptoms can often be confused with several infectious diseases.
Monitoring: Soil testing for pH before planting and tissue sampling during the season can help detect this nutrient imbalance.
Chemical Control: See the Chemical Disease Control section for more information.
Biological Control: No commercially effective controls are available.
Cultural Control: Maintain soil acidity levels between pH 6.0 and 6.5.
Powdery Mildew, Sphaerotheca fuliginea
Initial inoculum may come from old cucurbit debris left in the field, or it may be blown in on air currents from infested areas south of Virginia. The plants reveal the characteristic white mold when infected. The mold occurs on both sides of the leaves and often results in an upward cupping effect of leaves with a severe mildew infection. The resulting decrease in photosynthesis may cause significant reductions in the quality and yield of fruit. In contrast to downy mildew, which is more severe during wet weather, powdery mildew is actually inhibited by free moisture on leaf surfaces. Dense plant growth, low light intensity, and high fertility favor disease.
Monitoring: Check the upper and undersides of leaves by turning over at least 100 leaves in a field. If one infection site per 45 leaves is found, fungicides need to be applied.
Chemical Control: Alternate chlorothalonil plus Nova or Procure with chlorothalonil plus Pristine, Amistar, Cabrio, or Flint every seven days. See the Chemical Disease Control section for more information.
Biological Control: No commercially effective controls are available.
Cultural Control: Use tolerant varieties, which include Athena and Eclipse. Crop rotation and tillage options will have only a minor effect on powdery mildew control. However, removing plant debris at the end of the season may reduce overwintering of the fungus.
Scab, Cladosponum cucumerinum
This fungal disease can attack all parts of the plant. The unsightly scab lesions that develop on fruit are most damaging, usually making it unmarketable. The first signs of disease are usually pale green, water-soaked areas on the leaves and runners. These spots gradually turn gray to white and become angular in shape. The only disease that scab may be confused with is angular leaf spot. Many of the symptoms are the same. However, angular leaf spot is more likely to infect only the foliage, whereas scab infection occurs on both foliage and fruit.
Monitoring: Check for leaf lesions and lesions on runners during periods of cool, wet weather.
Chemical Control: See the Chemical Disease Control section for more information.
Biological Control: No commercially effective controls are available.
Cultural Control: Choose sites that have well-drained soils and are conducive to good air drainage to allow for rapid drying of foliage. Crop rotation with noncucurbits for two or more years is also very important.
Viruses (CMV, WMV-2, PRSV-W, and ZYMV)
Viruses can be spread in the field by insect feeding, cuttings, and infected seeds. In the cucumber mosaic virus (CMV), the leaves show a distinctive yellow and green mosaic pattern on the youngest leaves near the growing tip. Over time, the leaves become malformed and curled, stunting of the vines occurs, and little fruit is produced. The watermelon mosaic virus - II (WMV-2) causes the leaves to become distorted and blistered and displays the same yellow and green mosaic pattern on the newest leaves. If plants are infected young, they can become stunted. The fruit can become misshapen, dwarfed, mottled, or spotted. Papaya ringspot virus (PRSV-W), formerly known as watermelon mosaic virus - I (WMV-1), causes severe plant stunting. A green mosaic pattern is visible on the leaves and is usually accompanied by malformations, leaf distortions, and narrowing leaf blades. The fruit can be malformed and present a break in color pattern. Zucchini yellow mosaic virus (ZYMV) also causes plant stunting and exhibits a yellow mosaic pattern, leaf malformations, and dead patches on the leaves. In the fruit, deep cracks can occur, allowing secondary bacteria to invade the flesh of the fruit.
Monitoring: Monitoring your crop on a regular basis for disease will help you apply pesticides when needed.
Chemical Control: Soaps and oils can be used to control virus-transmitting aphids, but once the virus is established in the crop, there are no effective chemical controls available. Reduce insect vectors with insecticides. Remember, however, that insecticides are not always effective in reducing virus spread because the virus may have been transmitted before the insecticide kills the insect.
Biological Control: No commercially effective controls are available.
Cultural Control: Always use virus-resistant cultivars whenever possible, and keep weeds mowed around fields that may harbor viruses over the winter. Plant crops early to escape peak aphid season, and plant as far away from existing cucurbit plantings as possible to prevent aphid transmission of viruses from existing fields to new fields.
Chemical Disease Control
The list below contains all of the products available to producers for disease control in cantaloupe along with the recommended application rates of these chemicals. Always consult the label before making an application. PHI = Pre-Harvest Interval. REI = Re-Entry Interval.
Control recommendations were taken from 2004 Commercial Vegetable Production Recommendations-Virginia.10
NEMATODES
The root-knot nematode (Meloidogyne spp.) is the most important species of nematode affecting cantaloupes in Virginia.11 As the nematodes feed and multiply within melon roots, they retard uptake of water and growth of vines. Nematode problems can be magnified by hot, dry summers. The diagnostic feature of root-knot nematode infection is the presence of galls on roots of affected plants. Severely affected plants may have galls as large as 1 inch in diameter.
Symptoms and damage can mimic other diseases and pests, making identification nearly impossible to determine on site. Soil and root samples should be collected and analyzed by an expert for determination.
Monitoring: Both diagnostic and predictive nematode assay programs in Virginia provide data to producers on the numbers and kinds of nematodes in soil along with recommendations for control. Soil samples for diagnostic assays are processed without charge to determine the cause of production problems during the growing season. Predictive nematode assays are done on samples collected after harvest.
Chemical Control: When using soil fumigation, it is important that the fields be sufficiently prepared for planting. All crop debris and clods should be removed, and soil moisture should be adequate. Otherwise, soil fumigation will not be effective due to lack of penetration of all soil particles by the gaseous fumigant. It is also necessary to allow an aeration period between fumigant applications and planting. Otherwise, crop injury will occur. For recommendations, see the Chemical Nematode Control section below.
Biological Control: No commercially effective controls are available.
Cultural Control: Sanitation and good cultural practices are the best preventive measures against nematodes. Examples include obtaining nematode-free roots and washing soil from machinery and tools before using them at different locations. Crop rotation with nonhost crops, specifically grain crops, to lower nematode population size is highly recommended in the event of nematode activity.
Chemical Nematode Control12
Several chemicals are currently available for nematode control, although this may change in the next few years. Currently, the multipurpose soil fumigants chloropicrin, chloropicrin plus dichloropropene (Telone C-17, Telone C-35), metam-potassium (K-PAM HL), metam-sodium (Vapam HL), and methyl bromide (Terr-O-Gas 67, MC-33) are recommended for use in Virginia. In addition, dichloropropene (Telone II) is a soil fumigant used only for nematodes. The nonfumigant nematicide, oxamyl (Vydate L), is also recommended for use in cantaloupes. Typically, chemical controls are used only when cultural practices cannot provide adequate control. However, these chemicals are still important tools when other methods of control have failed.
Control recommendations were taken from 2004 Commercial Vegetable Production Recommendations-Virginia.13
WEEDS
The herbicides currently labeled for weed control in cantaloupe in Virginia work on annual grasses, certain perennial grasses, and certain broadleaf weeds. However, producers in Virginia are faced with a multitude of late-season broadleaf weeds, including common lambsquarters, common cocklebur, jimsonweed, mustards, and pigweed species. Successful weed management is vital to the production of quality cantaloupes. Weeds compete with the crop for light, space, nutrients and, particularly, water. Weed growth promotes disease problems and can harbor harmful insects and diseases. If not controlled, weeds can greatly reduce root quality and may interfere with the harvest.
Monitoring: Proper weed identification is an important part of effective weed control. Weeds observed in previous crops within a given field should be noted to aid in future herbicide decisions. It is also important to monitor the effectiveness of preplant incorporated and preemergent herbicides once the crop emerges.
Chemical Control: To provide additional pest control, a Special Local Need 24(c) label has been approved in Virginia for the postemergence and postharvest use of paraquat (Gramoxone Max 3SC). Recommended rates can be found in the Chemical Weed Control section below.
Biological Control:No commercially effective controls are available.
Cultural Control: Cultivation is a very important component of weed control. Weeds will outcompete a crop for nutrients, water, and sunlight, reducing yield and making the crop less profitable. Incorporating cultivation with herbicides is the best way to combat weeds and to produce a high yield. Crop rotation is also important to prevent domination of any one weed species year after year. Also, avoiding fields with a history of severe weed infestations may be appropriate.
Chemical Weed Control
The list below contains all of the fully labeled products available to producers for weed control in cantaloupe. Always consult the label before making an application. PHI = Pre-Harvest Interval. REI = Re-Entry Interval.
Use the following herbicides for weed control under plastic mulch or crop injury and/or poor weed control may result.
Black plastic mulch effectively controls most annual weeds by preventing light from reaching the germinated seedlings. Herbicides are used under plastic mulch to control weeds around the planting hole, and under the mulch when clear plastic is used. Trickle irrigation tubes left on the soil surface may cause weed problems by leaching herbicide away at emitters. The problem is most serious when clear plastic mulch is used. Bury the trickle tube several inches deep in the bed to reduce this problem. Delay punching the planting holes until seeding or transplanting.
Use the following herbicides to treat soil strips between rows of plastic mulch or crop injury and/or poor weed control may result.
Note: All herbicide rate recommendations are made for spraying a broadcast acre.
Preemergence:
Postemergence:
Use the following herbicides when seeding into soil without plastic mulch or crop injury and/or poor weed control may result.
Note: All herbicide rate recommendations are made for spraying a broadcast acre.
Preplant Incorporated:
Preplant Incorporated or Preemergence:
Preemergence:
Postemergence:
Postharvest:
Table 1: Effectiveness of herbicides recommended for weed control in cantaloupes.14
Developed and Written by:
Therese N. Schooley
Project Manager
Virginia
Polytechnic Institute and State University
Department of
Entomology
Virginia Tech Pesticide Programs (0409)
34 Agnew Hall
Blacksburg, VA 24061
Ph: 540-231-2086
Fax: 540-231-3057
E-mail: tschooley@vt.edu
Contributing Authors:
Diseases:
Christine M.
Waldenmaier
Research Specialist, Plant Pathology
Virginia
Polytechnic Institute and State University
Eastern Shore Agricultural
Research and Extension Center (0512)
33446 Research Drive
Painter, VA
23420-2827
Ph: 757-414-0724
Fax: 757-414-0730
E-mail: cwalden@vt.edu
Insects:
Thomas P.
Kuhar
Assistant Professor, Entomology
Virginia Polytechnic
Institute and State University
Eastern Shore Agricultural Research and
Extension Center (0512)
33446 Research Drive
Painter, VA 23420-2827
Ph:
757-414-0724
Fax: 757-414-0730
E-mail: tkuhar@vt.edu
Pesticides:
Michael J.
Weaver
Professor and Extension Pesticide Coordinator
Virginia
Polytechnic Institute and State University
Department of
Entomology
Virginia Tech Pesticide Programs (0409)
34 Agnew
Hall
Blacksburg, VA 24061
Ph: 540-231-6543
Fax: 540-231-3057
E-mail:
mweaver@vt.edu
Weeds:
Henry P.
Wilson
Professor, Weed Science
Virginia Polytechnic Institute and
State University
Eastern Shore Agricultural Research and Extension Center
(0512)
33446 Research Drive
Painter, VA 23420-2827
Ph:
757-414-0724
Fax: 757-414-0730
E-mail: hwilson@vt.edu
Cultural Practices:
Rikki
Sterrett
Associate Professor, Horticulture
Virginia Polytechnic
Institute and State University
Eastern Shore Agricultural Research and
Extension Center (0512)
33446 Research Drive
Painter, VA 23420-2827
Ph:
757-414-0724
Fax: 757-414-0730
E-mail: vators@vt.edu
Edited by:
Susan E.
Nessler
Project Coordinator
Virginia Polytechnic Institute and
State University
Department of Entomology
Virginia Tech Pesticide Programs
(0409)
34 Agnew Hall
Blacksburg, VA 24061
Ph: 540-231-8956
Fax:
540-231-3057
E-mail: snessler@vt.edu
On-Line Resources
C&P Press Online Crop Protection Reference
http://www.greenbook.net/
Crop Data Management Systems - Pesticide Labels
http://www.cdms.net/pfa/LUpdateMsg.asp
Insects and Related Pests of Vegetables
http://ipm.ncsu.edu/AG295/html
Pests of Vegetables and Fruit Trees
http://everest.ento.vt.edu/~idlab/vegpests/vegfact.html
Virginia Agricultural Statistics Service
http://www.nass.usda.gov/va/
Virginia Tech Pesticide Programs
http://www.vtpp.ext.vt.edu/
Virginia Tech Weed Identification Guide
http://www.ppws.vt.edu/weedindex.htm
1 Virginia Agricultural Statistics Bulletin and Resource Directory, 2001. Virginia Agricultural Statistics Service, Richmond, Virginia. Bulletin 77 (pp. 6, 54).
2 University of Georgia, Department of Horticulture. Vegetable Crops: http://www.uga.edu/vegetable/melon.html
3 Virginia Tech Cooperative Extension Publication 426-406, June 2000. Cucumbers, Melons and Squash: http://www.ext.vt.edu/pubs/envirohort/426-406/426-406.html.
4 Bratsch, A. D., Kuhar, T. P., Phillips, S. B., Sterrett, S. B., Waldenmaier, C., and Wilson, H. P., 2004. Commercial Vegetable Production Recommendations (No. 456-420), Virginia Cooperative Extension.
5 Swaider, J. M., Ware, G. W., and McCollum, J. P., 1980. Producing Vegetable Crops (4th ed.). Interstate Publishers, Inc. Danville, IL.
6 Bratsch, A. D., Kuhar, T. P., Phillips, S. B., Sterrett, S. B., Waldenmaier, C., and Wilson, H. P., 2004. Commercial Vegetable Production Recommendations (No. 456-420), Virginia Cooperative Extension.
7 Capinera, J. L., 2001. Handbook of Vegetable Pests. Academic Press, San Diego, CA.
8 "Cucumber Beetles." http://ipm.ncsu.edu/AG295/html/cucumber_beetles.htm.
9 Bratsch, A. D., Kuhar, T. P., Phillips, S. B., Sterrett, S. B., Waldenmaier, C., and Wilson, H. P., 2004. Commercial Vegetable Production Recommendations (No. 456-420), Virginia Cooperative Extension.
10 Bratsch, A. D., Kuhar, T. P., Phillips, S. B., Sterrett, S. B., Waldenmaier, C., and Wilson, H. P., 2004. Commercial Vegetable Production Recommendations (No. 456-420), Virginia Cooperative Extension.
11 Eisenback, J. D., Professor. Virginia Tech Department of Plant Pathology, Physiology, and Weed Science. Communications via email, September 6, 2003.
12 Bratsch, A. D., Kuhar, T. P., Phillips, S. B., Sterrett, S. B., Waldenmaier, C., and Wilson, H. P., 2004. Commercial Vegetable Production Recommendations (No. 456-420), Virginia Cooperative Extension.
13 Bratsch, A. D., Kuhar, T. P., Phillips, S. B., Sterrett, S. B., Waldenmaier, C., and Wilson, H. P., 2004. Commercial Vegetable Production Recommendations (No. 456-420), Virginia Cooperative Extension.
14 Bratsch, A. D., Kuhar, T. P., Phillips, S. B., Sterrett, S. B., Waldenmaier, C., and Wilson, H. P., 2004. Commercial Vegetable Production Recommendations (No. 456-420), Virginia Cooperative Extension.
