Fruiting vegetables
Fruiting vegetables: Aphids including the green peach aphid, Myzus persicae (Sulzer), Hemiptera: Aphididae
Biology: Aphids are small soft-bodied insects that feed on plants by inserting their stylet into the plant and removing large amounts of plant sap (Photos 51 and 52). Reproduction is both sexual and asexual and numerous generations occur each year. As a result population increases can be dramatic. But just as dramatic, populations often crash due to the action of natural enemies including fungal pathogens, parasitic and predatory insects. Insecticide application often decreases the effects of the beneficial organisms and large increases in aphid populations may result.
Management: Aphids are often naturally controlled by beneficial insects (predators and parasites) and fungi diseases. Use of foliar insecticide sprays disrupts the action of the beneficials and should only be used against very high and increasing levels of aphids. Many insecticides are effective against aphids on fruiting vegetables. Imidacloprid use is generally very effective and preserves natural enemies. Other insecticides may reduce aphid numbers but if used in early season may cause other insects to later reach pest status.
Back to Top
Fruiting vegetables: Blister beetles, Epicauta spp. Coleoptera: Meloidae
|
Photo 53 |
|
Photo 54 |
|
Photo 55 |
Biology: Adult beetles vary greatly in color from dark gray or black to yellow with black stripes (Photos 53 and 54) with black spots and up to 20 mm long. Adults emerge from pupa within the soil, mate and deposit up to a few hundred eggs in the soil. Damage on pepper, eggplant and okra is generally limited to foliage and when beetle populations are low to moderate, this foliar feeding has little impact on yield. Newly transplanted pepper and eggplant seedlings are more likely to sustain economic damage than older larger plants. Young eggplants may be killed by blister beetle attack.
Management: Adult blister beetles feed on foliage of pepper, eggplant, okra and many other host plants. Often damage is minimal and control is not justified. Thus, low numbers of blister beetles may be tolerated with a minimal effect on yield. In some cases, adults congregate in large numbers and rapidly consume large amounts of foliage (Photo 55). This may justify the application of insecticides including organo-phosphates, carbamates and pyrethroids. Because of the clumped distribution of blister beetles, insecticide application can often be limited to small areas of the field.
Back to Top
Fruiting vegetables: Colorado potato beetle, Leptinotarsa decemlineata (Say), Coleoptera: Chrysomelidae
|
Photo 56 |
|
Photo 57 |
|
Photo 58 |
Biology: Adult Colorado potato beetles are about 13 mm long and light yellow and black in color. Each forewing has 4 longitudinal black lines (Photo 56). In the spring adults emerge from the soil, mate and deposit up to a few hundred eggs on foliage of recently transplanted vegetables. Eggplant, along with potato, are preferred hosts although tomato, pepper and solaneous weeds, especially horsenettle, are also attacked. Several eggs are generally deposited on the foliage of a single plant (Photo 57). Larvae hatch in approximately one week and feed on foliage. Consumption of large amounts of foliage quickly occurs and eggplant transplants can be killed. Larvae are wingless and reddish-brown in color (Photo 58). After feeding for about 3 weeks, larvae move to the soil, pupate and begin the cycle again. In Arkansas two generations occur each year.
Management: The most susceptible stage of eggplant and pepper to the Colorado potato beetle is just after transplanting when plants are small and not vigorously growing. Transplanting when temperatures are warm and use of irrigation and fertilization will promote rapid plant growth and resulting damage from beetles will be minimized. If beetle numbers increase beyond acceptable levels, use of insecticides may be warranted. Traditional insecticides include organo-phosphates, carbamates and pyrethroids. Systemic insecticides such as imidacloprid, that are applied for other insects will likely provide effective control of Colorado potato beetles. Beneficial insects are also important in regulation of Colorado potato beetles. Minimizing the availability of host plants by plowing under eggplants after harvest and removal of solaneous weeds will aid in management. Recent increases in occurrence of Colorado potato beetle in Arkansas may be related to the use of reduced tillage practices in soybean. Producers are now permitting weeds to grow longer in the spring and early summer in soybean fields. Solenacious weeds are common and may provide an expanded host plant period for the Colorado potato beetle population to increase.
Back to Top
Fruiting vegetables: Cutworm, Agrotis spp., Lepidoptera: Noctuidae
Biology: Adult cutworms are dark grey moths with wingspans approaching 5 cm. After mating, females lay eggs on the host plant and larvae emerge in three to six days (Photo 59). As larvae develop the stem of seedling plants is often cut just above the soil line. Cutworms attack most vegetable plants.
Management: Adult cutworms are attracted to fields with plants or weeds where they deposit their eggs. Thus maintaining the field free of plants for at least two weeks prior to planting will reduce the cutworm problem. Crops should be rotated, especially with beans. Although labor intensive, wrapping the transplants with a paper collar from the root to about 5 centimeters above the ground will reduce cutworm feeding. Soil insecticides may be used with some success and will likely remain a critical element of cutworm management. In fields with persistent cutworm problems, incorporating insecticides into the soil should prove effective. Use of alternative and safer insecticides should be explored. Application of insecticides to foliage may be attempted in fields with problem cutworm populations but may not provide acceptable results.
Back to Top
Fruiting vegetables: Eggplant flea beetle, Epitrix fuscula (Crotch), Coleoptera: Chrysomelidae
|
Photo 60 |
|
Photo 61 |
|
Photo 62 |
Biology: Adult eggplant flea beetles are minute and only about 2-mm long and glossy black in color (Photos 60 and 61). The femur of each back leg is enlarged to provide the muscle needed for jumping “flea like”. In the spring adults emerge from overwintering sites, mate and deposit eggs in soil. Larvae feed on underground plant parts, pupate in the soil and emerge about one month from egg deposition. The adult is the damaging stage on foliage of transplants. Eggplant along with potato, are preferred hosts although solaneous weeds, esp. horsenettle, are also attacked. Adults cut shallow pits in the foliage resulting in a shot-hole appearance (Photo 62). Consumption of large amounts of foliage quickly occurs and eggplant transplants can be stunted and killed. Adults feed for several weeks during which eggs are being laid. In Arkansas several generations occur each year and damage can occur from early spring through late fall.
Management: The most susceptible stage of eggplant to flea beetles is just after transplanting when plants are small and not vigorously growing. Transplanting when temperatures are warm and use of irrigation and fertilization will promote rapid plant growth and resulting damage from beetles will be minimized. If beetle numbers increase beyond acceptable levels, use of insecticides may be warranted in both home gardens and commercially produced eggplant. Traditional insecticides include organo-phosphates, carbamates and pyrethroids. Systemic insecticides such as imidacloprid, that is applied for other insects, will likely provide effective control of flea beetles. In large eggplant fields most of the damage occurs within a few rows of the field edge. Insecticide application to only these edge rows may provide acceptable results. Once eggplant has several leaves, the effects of eggplant flea beetles on yield is greatly diminished and insecticide applications directed toward flea beetles can be terminated. Minimizing the availability of host plants by plowing under eggplants after harvest and removal of solaneous weeds will aid in management.
Back to Top
Fruiting vegetables: Noctuid caterpillars including Tomato fruitworm, Helicoverpa zea (Boddie) (Photo 63 and 64), Tobacco budworm, Heliothis virescens (Fabricius), Fall armyworm, Spodoptera frugiperda (J.E. Smith)(Photo 65), and Yellow striped armyworm, Spodoptera ornithogalli (Guenee) (Photo 66). Lepidoptera: Noctuidae
|
Photo 63 |
|
Photo 64 |
|
Photo 65 |
|
Photo 66 |
|
Photo 67 |
Biology: Several caterpillars of the family Noctuidae attack solaneous crops including eggplant, pepper and okra. Behavior of each is similar. During mild winters in Arkansas the insects overwinter as pupae that are located within the upper 10 cm of soil. Adults emerge in early spring and are large bodied moths and are covered in scales that often dislodge and give the appearance of being dusty (Photo 67). In severe winters pupae mortality may be substantial in northern Arkansas and the initial source of spring moths is from migration from more southern areas. Shortly after emergence, moths mate and begin to lay eggs on foliage and stems. Eggs of tomato fruitworm and tobacco budworm are laid individually while armyworm eggs may be laid in masses of up to 30. Eggs hatch within two to six days depending on temperature and emerging larvae feed on foliage, blooms or fruit. The color and stripe pattern of larvae vary greatly and at maturity larvae may approach 5 cm in length. Foliar damage is generally limited and usually does not reduce yield. However, when fruit is present, damage may be excessive and control is often required. Multiple generations of caterpillars occur each season and generations overlap. Caterpillars feed on numerous host plants both wild and cultivated.
Management: Numerous beneficial organisms help to suppress the Noctuid populations including insect diseases, predatory and parasitic insects such as Trichogramma wasps. Efforts at conserving these beneficials is of utmost importance. To accomplish this, immediately after transplanting, plants should be scouted for caterpillars. After transplanting, the use of “hard insecticides” should be delayed for as long as possible. Low numbers of caterpillars may be tolerated with a minimal effect on yield. In small gardens removal and destruction of infested fruit will prevent the caterpillars from moving to adjacent fruit. By stepping on infested fruit, larvae can be killed. Larger caterpillars on foliage can be removed by hand. If numbers of caterpillars increase beyond acceptable levels, use of insecticides is warranted. Bacillus thuringiensis (BT) likely offers the best alternative to the “hard insecticide”. Also, several newer BT’s (Biobit) likely offer improved performance. Again, the objective of early season use of “soft” insecticides is to promote the development and prolong the effectiveness of beneficial organisms. Other “soft” insecticides include spinosad and indoxicarb. Also, after exposure to “soft insecticides”, caterpillars will generally stop feeding but death may not occur for several days. Thus determining the effectiveness of the “soft insecticide” should be delayed for at least one week. If high levels of caterpillar populations persist despite use of “soft insecticides”, use of traditional insecticides including organo-phosphates, carbamates or pyrethroids may be required. Sanitation, including destruction of crops immediately following the last harvest, may have some effectiveness in reducing damage in subsequent plantings. Use of corn as a trap crop may also reduce the presence of fall armyworm and tomato fruitworm in pepper, eggplant and okra.
Back to Top
Fruiting vegetables: Japanese beetle, Popillia japonica Newman, Coleoptera: Scarabaeidae
Biology: The Japanese beetle was first detected in Arkansas near Lowell in the northwest corner of the state during 2000. Adult beetles were initially reported on snap bean, oak trees and rose of Sharon shrubs. Since first detection during 2000, distribution of adults has increased to include most of the northwest quarter of the state with isolated reports from much of the remainder of Arkansas. The insect is likely to move to the entire state within a short number of years. Japanese beetle adults are about 13 mm in length and golden green in color (Photo 68). Characteristic white markings are evident on the sides of the abdomen. In Arkansas, adult beetles emerge from pupa in the upper layer of soil in mid-June and feed gregariously on many host plants. Locally produced vegetables sustaining the most damage include okra (Photo 69), sweet corn and snap bean. Most other vegetables, many fruit and many wild hosts are also attacked. Adults have become common in northwest Arkansas from mid-June until August. During this period adults mate and females lay eggs in shallow burrows in the soil supporting grasses. Larvae hatch in about 2 weeks and feed on grass roots causing significant damage in high value grasses including golf greens and yards. Larvae density is often high with more than 10 per square foot. Because of the abundance of pastures in northwest Arkansas, the Japanese beetle population has greatly increased in just 8 years. Larvae overwinter in the ground, pupate in spring and emerge the following summer. Only one generation occurs annually in Arkansas.
Management: Although some effort at controlling the larvae stage with insecticides and a disease of the Japanese beetle, i.e., milky spore, has been tried, this has little impact on the adults that damage vegetables. There is simply too much pasture available that is not treated and emerging adults can easily fly long distances into vegetable fields. Thus, successful management efforts can only be directed toward adult beetles. First, foliar damage from Japanese beetles often appears substantial but many vegetables such as okra and snap bean can sustain large amounts of damage with little effect on yield. Promoting rapid plant growth with proper fertilization and irrigation will aid the plant to withstand the damage. Pheromone traps are available and very effective in trapping adult Japanese beetles. Regardless of the trap’s effectiveness, many more beetles are capable of avoiding capture and attack susceptible plants. If beetle numbers increase beyond acceptable levels, use of insecticides may be warranted. Traditional insecticides are usually effective against adults but migration of new adults may require repeated insecticide applications.
Back to Top
Fruiting vegetables: Eggplant lace bug, Gargaphia solani Heidemann. Hemiptera: Tingidae
Biology: Lace bugs are true bugs having the front half of the fore wing hardened while the rear portion is membranous. Adults are tan in color and only about 4mm in length (Photo 70). Immature bugs or nymphs resemble the adults but are wingless (Photo 71). Both adults and immatures are flattened. After mating, the female lace bug lays an egg mass containing up to about 50 eggs on the leaf bottom of eggplant. After hatching, immatures, along with the mother, remain in a group on the leaf surface and begin to feed. A beak-like stylet is inserted into the plant tissue, digestive fluids are injected and plant sap is withdrawn.
Management: Low numbers of lace bugs may be tolerated with a minimal effect on yield. If lace bug numbers increase beyond acceptable levels, use of a insecticides may warranted. Sanitation, including destruction of crops immediately following the last harvest, may have some effectiveness in reducing damage in subsequent plantings.
Back to Top
Fruiting vegetables (pepper): Pepper weevil, Anthonomus eugenii Cano. Coleoptera: Curculionidae
|
Photo 72 |
|
Photo 73 |
|
Photo 74 |
|
Photo 75 |
Biology: The pepper weevil has not been a significant pest on pepper in Arkansas in recent years. The reason for this is likely its inability to overwinter in most of the state. Thus, populations must develop from weevils migrating into the state on pepper transplants or fruit obtained from more southern states. Adult pepper weevils are very small (3 mm long) weevils with scattered white markings over a dark gray colored body (Photo 72). Adults feed on buds and fruit of pepper and females deposit a single egg into a feeding crevice. After 3 to 7 days, larvae hatch and burrow into the fruit. Feeding is within the fruit and renders the fruit unmarketable. Mature larvae are cream colored and are about 5 mm long (Photo 73). Pupation occurs within the fruit (Photo 74), adults emerge through an exit hole in the fruit (Photo 75) and after about one week to begin the cycle again. Solaneous weeds also serve as hosts for pepper weevil in Arkansas. Pepper weevil occurs throughout the state but to date impact has been minimal.
Management: If pepper seedlings are purchased from areas where the weevil can overwinter, care should be taken that the transplants are free of pepper weevil. This slows migration into Arkansas and results in slower population increases. Peppers should be searched for damage from the larvae. Shaking plants vigoursly may cause infested fruit to drop from the plant. These can be inspected for larvae. Adult weevils are small but by careful observation or other sampling methods such as sweeping, adults can be detected. Low numbers of pepper weevil may be tolerated with a minimal effect on yield. If pepper numbers increase beyond acceptable levels, use of insecticides may be warranted.
Back to Top
Fruiting vegetables: Spider mite, Tetranychus urticae Koch. Acari: Tetranychidae
Biology: Not true insects, mites are minute (<.5mm in length) and feed by extracting sap from leaves. The result of this feeding is a whitish or bronze appearance on the leaves. When large numbers of mites are present, silk webbing can be seen on leaves and stems (Photos 76 and 77). Adult females deposit up to about 100 eggs on foliage. Larvae emerge in as few as 3 days and begin to feed. Within about 1 week adults may appear and the cycle is repeated. Multiple generations occur each year. Hot dry weather promotes mite increase.
Management: Shortly after transplanting, plants should be scouted for mites. Low numbers of mites may be tolerated with a minimal effect on yield. If mite numbers increase beyond acceptable levels, use of an acaricide such as Kelthane is warranted. Mites feed predominately on the bottoms of foliage. Thus, acaricides must be applied in such a manner in which the mite comes into contact with the acaricide, i.e., apply the acaricide to the leaf bottom. Use of a surfactant and a large volume of water should assist the spread of the material to the bottom surface. Sanitation, including destruction of crops immediately following the last harvest, may have some effectiveness in reducing damage in subsequent plantings. In areas with a history of high mite numbers, removal of adjacent weeds several weeks prior to transplanting may reduce later infestations.
Back to Top
Fruiting vegetables: Stink bugs. Hemiptera: Pentatomidae and leaffooted bugs. Hemiptera: Coreidae
|
Photo 78 |
|
Photo 79 |
|
Photo 80 |
|
Photo 81 |
Biology: Stink bugs are true bugs having the front half of the fore wing hardened while the rear portion is membranous. Adult size and color vary greatly by species. Pentotamids (Photos 78, 79 and 80) are shield shaped about 15mm long while Coreids (Photo 81) are more oblong and are up to 25mm long. Some have flattened expansions on the hind legs and are termed leaf-footed bugs. Immature stink bugs or nymphs resemble the adults but are wingless. Stinkbugs feed on most plant structures but damage is most evident on fruit. A beak-like stylet is inserted into the plant tissue, digestive fluids are injected and plant sap is withdrawn. On fruit, this leaves a very small scab on the surface. Fruit damaged during early stages of formation may be distorted. Multiple stink bug generations occur each year.
Management: Low numbers of stink bugs may be tolerated with a minimal effect on yield. If stink bug numbers increase beyond acceptable levels, use of insecticides may be warranted. Sanitation, including destruction of crops immediately following the last harvest, may have some effectiveness in reducing damage in subsequent plantings. Numerous beneficial organisms affect stink bug populations including some beneficial stink bugs and insecticide use may reduce their effectiveness.
Back to Top
Fruiting vegetables (eggplant): Green tortoise beetle, Metriona bicolor (Fabricius), Coleoptera: Chrysomelidae
Biology: Adult beetles are up to 7mm in length, oval shaped and metallic yellow-green (Photo 82). Tortoise beetles overwinter on plant debris, mate and deposit up to a few hundred eggs on eggplant foliage. Larvae hatch in about one week and feed on eggplant foliage. This damage is characteristic oval. Damage is usually minimal but occasionally plant growth of recently transplanted eggplant seedlings can be retarded by excessive feeding. Tortoise beetle larvae are also oval in shape but possess numerous spines over much of the body. Larvae also expel dry excrement that is cemented to their posterior (Photo 83). As growth continues, this excrement curls upward and forms a umbrella-like structure over the larvae. Tortoise beetle larvae complete development in approximately 3 weeks, pupate and the next generation of adults emerges in about one week. Newly transplanted eggplant seedlings are more likely to sustain economic damage than older larger plants. Multiple generations occur each year.
Management: The most susceptible stage of eggplant tortoise beetles is just after transplanting when plants are small and not vigorously growing. Transplanting when temperatures are warm and use of irrigation and fertilization will promote rapid plant growth and resulting damage from larvae will be minimized. Low to moderate numbers of adult tortoise beetles may be tolerated with a minimal effect on yield. If beetle numbers increase beyond acceptable levels, use of insecticides may be warranted. Many traditional insecticides provide effective control of tortoise beetles.
Back to Top
Fruiting vegetables: Whitefly, Bemisis spp., Hemiptera: Aleyrodidae
Biology: Whiteflies generally do not overwinter in Arkansas due to cold weather. Recent problems on vegetables in Arkansas may be related to a concurrence of several mild winters along with hot dry summers. Additional sources of whiteflies in spring months may be from greenhouse production of vegetables and seedlings during winter. Plants grown for an extended period in greenhouses frequently develop significant whitefly populations. Adult whiteflies are minute (about 1 mm in length) and white in color (Photo 84). Eggs are inserted into leaf tissue and nymphs also known as “crawlers” emerge and feed by extracting sap from plants (Photo 85). Not only does this feeding damage the plant but whiteflies are also responsible for virus disease transmission. Shortly after hatching, nymphs attach themselves to the underside of the leaf surface while they feed one to four weeks. Developmental time is greatly dependent on temperature. Whiteflies can be found on most vegetable crops and also occur on numerous alternative hosts including weeds. In Arkansas, velvet leaf is a preferred alternate host.
Management: In Arkansas vegetable fields, most fruiting vegetables are planted in late spring when growing conditions are favorable for rapid plant growth. Whiteflies may be found but in Arkansas, fruiting vegetables generally outgrow the whitefly population. Harvest usually occurs prior to a high whitefly population increase. Location of fields away from greenhouses that hold vegetables through the winter may reduce whitefly migration into the field. Many weeds, especially velvet leaf and some Solaneous weeds, harbor large whitefly populations. Removal of these alternate host plants several weeks prior to the production season will reduce the likelihood of high whitefly populations at planting. Immediately after plants emerge, vegetables should be scouted for whiteflies. If detected early in the season use of insecticides may be warranted. Proper selection of insecticides such as imidacloprid should be effective against whiteflies and its use during early parts of the season may preserve natural enemies and reduce the occurrence of secondary pests. Sanitation, including destruction of crops immediately following the last harvest, will likely reduce damage in subsequent plantings.
Greenhouse management: Significant whitefly problems are now reported annually in greenhouses in Arkansas. These problems have some common characteristics. Plants are grown for extended periods and subsequent plantings often occur in greenhouses already producing plants. This provides an extended period of host plant availability with optimal developmental temperature for whiteflies. Natural enemy movement into the greenhouse is also reduced. To reduce the impact of whiteflies in greenhouses, this period of host plant availability should be reduced. Sanitation, including removal and destruction of plants immediately following harvest, will likely reduce whitefly population increase. If possible, all susceptible plants including weeds on the greenhouse floor should be removed for at least 2 weeks. Immediately after plants emerge, they should be scouted for whiteflies. If detected, use of insecticides is warranted. Proper selection of insecticides such as imidacloprid should be effective against low populations of whiteflies. Once populations build to noticeable numbers, imidacloprid is not likely to control the continuous emerging of adults from immature stages. Additional insecticides effective in greenhouse whitefly management include resmethrin and kinoprene. Beneficial insects are available for purchase and may provide some impact in greenhouse production.
Back to Top
|
