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Bean & Southern Pea Insect Pests

Severe cowpea aphid (Aphis craccivora) infestation. Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org

Severe cowpea aphid (Aphis craccivora) infestation.
Clemson University – USDA Cooperative Extension Slide Series, www.insectimages.org

Major Seedling Feeders

Aphids: Aphids (Aphis species and Macrosiphum euphorbiae) are soft-bodied “plant lice,” about 1/16 to 1/8 inch in length and are usually green, although some species are yellow, pink, brown, or black. They are most prevalent during cool, dry weather on small plants. Heavy populations of aphids can stunt plants by withdrawing large volumes of plant juices and delaying maturity

Treatments for aphid control should begin at any time colonies are found. In the home garden, spray foliage with soapy water, then rinse with clear water. Alternatively, use an insecticidal soap spray. Planting in aluminum foil that has been laid on the planting bed, as well as filling yellow pans with water to trap the aphids are also effective control measures. Once the weather warms up, natural enemies usually control aphids.

Thrips: Thrips (Frankliniella species) are small, slender, agile insects, rarely as long as 1/8 inch. They are commonly found in flowers of peas and beans but will also feed on leaves. Their presence in flowers at early bloom may result in poor fruit set due to pollination interference by thrips feeding.

Western flower thrips (Frankliniella occidentalis) damage to bean leaf. Whitney Cranshaw, Colorado State University, www.insectimages.org

Western flower thrips (Frankliniella occidentalis) damage to bean leaf.
Whitney Cranshaw, Colorado State University, www.insectimages.org

Western flower thrips adult (Frankliniella occidentalis). Frank Peairs, Colorado State University, www.insectimages.org

Western flower thrips adult (Frankliniella occidentalis).
Frank Peairs, Colorado State University, www.insectimages.org

Field observations indicate that three thrips per flower may interfere with pollination and cause defectively shaped pods. After pods are 1- to 2-inches long, the damage is primarily cosmetic since small blisters are generally the only result of their feeding.

In the home garden, planting in aluminum foil that has been laid on the bed tends to repel thrips. Insecticidal soaps may give adequate control.

Lesser corn stalk borer larvae (Elasmopalpus lignosellus) and damage to stem. Riley, University of Georgia, www.insectimages.org

Lesser corn stalk borer larvae (Elasmopalpus lignosellus) and damage to stem.
Riley, University of Georgia, www.insectimages.org

Lesser Cornstalk Borer: The lesser cornstalk borer (Elasmopalpus lignosellus) is the larval (immature) stage of a small (½-inch long) brownish-yellow moth. Moths leave field corn when it begins to dry and enter late-planted fields of peas and beans. The moths lay eggs around the base of emerging plants. These eggs quickly hatch into larvae, which are small, slender caterpillars with green, blue, or brown bands around each body segment. The larvae bore into the stalks of young plants near the soil line and tunnel up and down the stalks. A silken tube is usually attached to the entrance hole where the larvae bore into the stem, and the larva may sometimes be found in this tube. Plants damaged by lessers become stunted, wither, and later die. Late plantings (those made after July 1) on sandy soil during hot, dry conditions often result in 30 to 50 percent stand loss.

Major Foliage/Stem Feeders

Several kinds of beetles and caterpillars may be found feeding on the foliage of peas and beans. The combined feeding of all or heavy populations of one species may require insecticide treatments. Peas and beans are fast-growing plants with heavy canopy due to an overabundance of leaves. Research has shown that 30 percent leaf loss prior to the bloom stage will not result in reduced yield or quality. In addition, these plants can tolerate up to 15 percent leaf loss during bloom and pod-fill stages without significant drops in yield or quality.

The following pests are considered major foliage feeders, and their combined feeding may require treatments to prevent yield and quality loss.

Eggs, larvae, and adult Mexican bean beetles (Epilachna varivestis). Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org

Eggs, larvae, and adult Mexican bean beetles (Epilachna varivestis).
Clemson University – USDA Cooperative Extension Slide Series, www.insectimages.org

Mexican Bean Beetle: The Mexican bean beetle (Epilachna varivestis) is ¼- to 1/3- inch long, very convex, and yellow to coppery-brown. Each wing cover has eight small, black spots that form three rows across the body. Some of the beetles appear at the emergence of the earliest plantings, whereas others may wait until nearly two months later to leave their overwintering quarters.

After feeding on beans a week or two, the adult female deposits yellow eggs in groups of 20 to 50 on the undersides of leaves. The eggs hatch in one to two weeks, depending on temperature, and the larvae (immature forms) feed for two to four weeks. Both larvae and adults feed on the undersides of leaves, leaving the upper surface more or less intact. The larvae consume areas of leaf tissue, leaving veins between the chewed areas, which gives the leaf a skeletonized, lacy appearance. When abundant, larvae and adults will also feed on stems and pods. When full-grown, larvae are 1/3-inch long, yellow, and armed with black-tipped spines. Larvae change to pupae (the nonfeeding stage where the larvae change to adults) on plants — usually on the undersides of undamaged leaves. The pupal stage is cemented to leaves, and the adult emerges in about 10 days. From egg to adult requires about one month, and there are usually three generations per year. During some years, there may be a partial fourth generation.

Since most damage occurs during July and August, quick-maturing varieties of green beans planted very early or during late summer may escape damage. The snap bean varieties: ‘Wade’ and ‘Black Valentine’ are resistant or tolerant to Mexican bean beetles. In the home garden, handpick and destroy beetles and egg masses. Destroy crop refuse after harvest by working it into the soil or adding it to a compost pile.

Bean leaf beetle (Cerotoma trifurcata). Natasha Wright, Florida Department of Agriculture and Consumer Services, www.insectimages.org

Bean leaf beetle (Cerotoma trifurcata).
Natasha Wright, Florida Department of Agriculture and Consumer Services, www.insectimages.org

Bean Leaf Beetle: The bean leaf beetle (Cerotoma trifurcata) is rarely a serious problem on beans or peas grown in South Carolina. The adults are about 1/5- to ¼- inch long. They vary considerably in color and markings but are typically red to yellow, with three or four black spots in a row along the inner edge of each wing cover. Damage caused by bean leaf beetles is twofold: (1) girdling of stems near the soil line and (2) large irregular holes chewed in leaves. Damage to beans and peas early in the season may result in stand reduction.

Stippling of bean leaves caused by two spotted spider mite (Tetranychus urticae). Whitney Cranshaw, Colorado State University, www.insectimages.org

Stippling of bean leaves caused by two spotted spider mite (Tetranychus urticae).
Whitney Cranshaw, Colorado State University, www.insectimages.org

Spider Mites: Two-spotted spider mites (Tetranychus urticae) are minute, eight-legged pests that are more closely related to spiders than to insects. Adults and immature stages appear as tiny specks on the undersides of leaves where they pierce the leaf surface and suck sap. Lightly infested leaves develop tiny whitish speckled spots, while heavily infested leaves turn pale yellow or bronze-colored and dry up. The undersurfaces of leaves usually are covered with silken webs over which the mites crawl. Spider mites develop rapidly during hot, dry weather, and one generation can be completed in as few as eight days.

Insecticidal soaps generally offer adequate control when applied before the numbers are too high. Additionally, many mites can be removed with a strong spray of water. Natural enemies such as lady bugs are important natural controls.

Lima bean vine borer larva (Monoptilota pergratialis) and damage. Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org

Lima bean vine borer larva (Monoptilota pergratialis) and damage.
Clemson University – USDA Cooperative Extension Slide Series, www.insectimages.org

Lima Bean Vine Borer: The lima bean vine borer (Monoptilota pergratialis) is an occasional pest of the large-stemmed bean varieties. The mature larva (caterpillar) is 7/8-inch long, bluish-green with a tint of pink on its back, and has a yellowish-brown plate behind its dark head capsule. It burrows into stems, typically just above or below nodes (that part of the stem from which a leaf grows), and hollows out cavities. Infested stems form galls (a tumor-like swelling), which eventually turn brown and develop a woody texture. Infested plants are weakened and have lower yields.

Cabbage looper larva (Trichoplusia ni). Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org

Cabbage looper larva (Trichoplusia ni).
Clemson University – USDA Cooperative Extension Slide Series, www.insectimages.org

Cabbage Looper: The cabbage looper (Trichoplusia ni) is another defoliator of peas and, to a lesser extent, beans. This larva (caterpillar) is green with a thin white line along each side of the body and two others near the middle of the back. Damage caused by loopers is ragged foliage. They rarely reach treatment status on peas and beans in the absence of other foliage feeders. The heaviest populations usually occur on late-planted crops.

Major Pod Feeders

Cowpea Curculio: The cowpea curculio (Chalcodermus aeneus) is the most destructive insect pest of southern peas grown in South Carolina. Cowpea curculios are rarely a problem on snap beans. Small, brown, wart-like or blister-like spots are found on pods damaged by curculios. These are caused when the adult punctures the pod to feed or lay eggs. Damaged peas have small, dark, indented spots and often contain grubs.

Cowpea curculio adult (Chalcodermus aeneus). Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org

Cowpea curculio adult (Chalcodermus aeneus).
Clemson University – USDA Cooperative Extension Slide Series, www.insectimages.org

The cowpea curculio overwinters (survives the winter) as an adult in crop refuse or grass in the field or on the border of the field. Tufts of broom sedge, particularly at edges of woods, are favorite hiding places for overwintering adults. The adult is an oval, hump-backed, bronze-tinged, black “snout” beetle that has small dents on the wing covers and on the upper side of the body. It is about ¼-inch long. Adults begin to leave their winter quarters in March or early April. This emergence continues until June or July or about the time that the first peas are available for egg laying. These overwintering adults are long-lived and may survive through August.

Eggs are laid as soon as peas are formed in the pods. The weevil (also called the “snout” beetle) punctures the pod and chews a small hole in the surface of the pea. A single egg is laid in each hole. A legless, pale yellow, brown-headed grub hatches from this egg.

The grub feeds on one or more peas before it reaches its full size of slightly more than ¼ inch long. It then chews an exit hole through the pod and drops to the ground. It enters the soil to a depth of about 1 inch and transforms into a pupa (a nonfeeding stage where the larva changes into an adult).

Approximately seven or eight days elapse from the time that the eggs are laid until the grubs emerge from the pod. The larvae pupate (transform to pupae) about six days after they leave the pod. About 21 to 50 days are required to complete the life cycle. There are two generations each year. Because eggs are laid over an extended period of time, generations overlap, and all stages can be present on southern peas at the same time.

Late southern peas isolated from early peas are usually not as severely damaged as early peas. Wild host plants produce pods that attract many curculios, and these can be a source of infestation.

The only feasible approach to the control of curculios is a preventive spray program. The current spray schedule recommended begins with a spray at first bloom and repeat treatments made on a five- to seven- day schedule.

Corn earworm larva (Helicoverpa zea) on soybean. Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org

Corn earworm larva (Helicoverpa zea) on soybean.
Clemson University – USDA Cooperative Extension Slide Series, www.insectimages.org

Corn Earworm: The corn earworm (Helicoverpa zea) is primarily a problem on late-planted peas and beans, but early plantings may also be attacked. These worms vary greatly in color from a light green or pink to brown or nearly black and are lighter on the underparts. They are marked with alternating light and dark stripes running lengthwise on the body. The head is yellow and unspotted, and the legs are dark or nearly black. The corn earworm chews holes in both foliage and pods but prefers the latter. Levels requiring insecticide treatment are 5 percent damaged pods or one larva per 3 feet of row.

Tarnished plant bug (Lygus lineolaris). Scott Bauer, USDA Agricultural Research Service, www.insectimages.org

Tarnished plant bug (Lygus lineolaris).
Scott Bauer, USDA Agricultural Research Service, www.insectimages.org

Tarnished Plant Bug: The tarnished plant bug (Lygus lineolaris) is a pest of snap and lima beans but rarely reaches pest status on southern peas. The bean growth period during which plant bugs are most important is full-bloom. The bugs withdraw plant sap and inject toxic saliva into the plant. The toxins may halt the development of blooms and young pods and cause dark spots to develop on older pods that are attacked.

The adult bugs are about ¼-inch long by less than half as broad, flattened, and oval in outline. They are a general brown color mottled with small, irregular patches of white, yellow, reddish-brown, or black. Nymphs (immature forms) are similar in shape to adults, with four black spots on the back. By late summer, adults and nymphs are numerous, but because of their color and shy hiding habits are not easily noticed. Late-planted beans are highly susceptible to attack and should be checked closely during the bloom stage. Treatments for bugs should be made when there is an average of one bug per 6 feet of row.

Southern green stink bug adult (Nezara viridula). Merle Shepard, Gerald R. Carner, and P.A.C Ooi, Insects and their Natural Enemies Associated with Vegetables and Soybean in Southeast Asia, www.insectimages.org

Southern green stink bug adult (Nezara viridula).
Merle Shepard, Gerald R. Carner, and P.A.C Ooi, Insects and their Natural Enemies Associated with Vegetables and Soybean in Southeast Asia, www.insectimages.org

Stink Bugs: The southern green stink bug (Nezara viridula) is a serious pest of lima beans and snap beans during late summer and fall. These bugs are shield-shaped, bright green, bad-smelling, flattened, and about 5/8-inch long. The young (nymphs) are similar in shape and have black markings. Stink bugs damage beans in both the nymph and adult stages by sucking juices and injecting toxins. Although they may feed on leaves, pods are preferred. External signs of stink bug feeding on pods of snap bean show up as clear or water-soaked areas. On lima beans, the external damage on pods is not as clear. Inside the pod, developing beans become brown after bugs inject toxins and introduce yeast infections.

On snap beans, insecticide treatment is necessary during the bloom stage when there is an average of one bug per 10 feet of row. Lima beans are more sensitive to damage, and insecticide treatment is needed in the bloom stage when there is an average of one bug per 15 feet of row.

Control of Bean & Southern Pea Insects

Consult the discussion under each pest listed on this fact sheet for the “economic threshold” or the level of pest populations or plant injury necessary to warrant control measures.

The first choice for control of insect pests on vegetables always should be the lesser toxic pesticides. These will be less harmful to beneficial insects and have a much shorter pre-harvest interval or waiting period between spraying the crop and harvesting the vegetables. More than one application of an insecticide is typically required to control a pest. Always follow all label directions and observe waiting periods until harvest (pre-harvest interval).

Table 1. Natural, Less Toxic Pesticides and Contact Pesticides to Control Bean Pests.

Pests Natural, Less Toxic Pesticides Contact Pesticides
Aphids Insecticidal soap
Neem oil extract
Pyrethrin
Bifenthrin
Cyhalothrin
Cypermethrin
Malathion
Bean Leaf Beetle Pyrethrin
Neem oil extract
Insecticidal soap
Spinosad
Bifenthrin
Cyhalothrin
Cypermethrin
Thrips Insecticidal soap
Spinosad
Bifenthrin
Cyhalothrin
Cypermethrin
Corn Earworm

Bean Looper

Bacillus thuringiensis (B.t.)
Pyrethrin
Neem oil extract
Spinosad
Bifenthrin
Cyhalothrin
Cypermethrin
Cowpea Curculio Pyrethrin
Neem oil extract
Bifenthrin
Cyhalothrin
Cypermethrin
Lesser Cornstalk Borer Bifenthrin
Cyhalothrin
Cypermethrin
Lima Bean Borer Bifenthrin
Cypermethrin
Mexican Bean Beetle Pyrethrin
Neem oil extract
Bifenthrin
Cyhalothrin
Cypermethrin
Malathion
Spider Mites Insecticidal soap Malathion
Bifenthrin
Stink bug

Tarnished Plant Bug

Stink Bug Traps* Bifenthrin
Cyhalothrin
Malathion
Japanese Beetles Pyrethrin
Neem oil extract
Bifenthrin
Cyhalothrin
Cypermethrin
Cucumber Beetle Pyrethrin
Neem oil extract
Soil drench with parasitic nematodes to control larvae
Bifenthrin
Cyhalothrin
Cypermethrin
Grasshopper Bifenthrin
Cyhalothrin
Cypermethrin
Malathion
Lygus Bugs Bifenthrin
Cyhalothrin
Cypermethrin
Malathion
Whiteflies Insecticidal soap Bifenthrin
Cyhalothrin
Cypermethrin
Cutworms Protective collars
Molasses & grain bait with B.t.
Bifenthrin
Cyhalothrin
Cypermethrin
*Reduced damage by stink bugs may be obtained by the use of stink bug traps placed near but not in the garden. Examples are Rescue Brand Reusable Stink Bug Traps, for sale at planetnatural.com, and Ambush Brand Stink Bug traps, for sale at gardensalive.com.

Table 2. Insecticides for Bean & Southern Pea Pest Control.

Pesticide Active Ingredient Pre-Harvest Intervals (Days) Examples of Brand Names & Products
Natural, Less Toxic Insecticides
Bacillus thuringiensis (B.t.) 0 Bonide Thuricide B.t. Concentrate
Garden Safe Bt Worm & Caterpillar Killer Concentrate
Monterey B.t. Concentrate; & RTU
Natural Guard Caterpillar Killer Spray with Bt Conc.
Safer Brand Caterpillar Killer Concentrate
Southern Ag Thuricide B.t. Caterpillar Control Concentrate
Tiger Brand Worm Killer Concentrate
Insecticidal Soap 0 Bonide Insecticidal Soap Multi-Purpose Insect Control RTU
Espoma Organic Insect Soap RTU
Garden Safe Insecticidal Soap Insect Killer RTU
Miracle Gro Nature’s Care Insecticidal Soap RTU
Natria Insecticidal Soap RTU
Natural Guard Insecticidal Soap Concentrate
Safer Brand Insect Killing Soap Concentrate; & RTU
Safer Brand Fruit & Vegetable Insect Killer RTU
Whitney Farms Insecticidal Soap RTU
Neem Oil Extract 0 Bonide Neem Oil Fungicide, Miticide & Insecticide
Concentrate; & RTU
Bonide Rose Rx 3-in-1 Concentrate; & RTU
Concern Garden Defense Multi-Purpose Spray Concentrate
Espoma Neem Oil 3-in-1 RTU
Ferti-lome Rose, Flower & Vegetable Spray Concentrate
Garden Safe Fungicide 3 Concentrate; & RTU
Garden Safe Neem Oil Extract Concentrate
Monterey 70% Neem Oil Fungicide, Insecticide & Miticide
Concentrate; & RTS
Natria Neem Oil Concentrate; & RTU
Safer Brand Neem Oil RTU OMRI
Southern Ag Triple Action Neem Oil Concentrate
Pyrethrin 0 Monterey Bug Buster-O
Monterey Pyganic Gardening
Southern Ag Natural Pyrethrin Concentrate
Spinosad 3

(28 days for dried beans & dried peas)

Bonide Captain Jack’s Dead Bug Brew Concentrate; & RTU
Ferti-lome Borer, Bagworm & Leafminer Spray Concentrate
Monterey Garden Insect Spray Concentrate
Natural Guard Spinosad Landscape & Garden Insecticide RTS
Southern Ag Conserve Naturalyte Insect Control Concentrate
Contact Insecticides
Bifenthrin 3 Ferti-lome Broad Spectrum Insecticide Concentrate
Monterey Mite & Insect Control Concentrate
Cyhalothrin (lambda) 7 Spectracide Triazicide Insect Killer for Lawns & Landscapes
Concentrate; & RTS
Martin’s Cyonara Lawn & Garden Insect Control Concentrate;
& RTS
Cypermethrin 1 (21 days for dried beans & dried peas) Gardentech Sevin Insect Killer Concentrate; & RTS
Gordon’s Bug-No-More Lawn & Garden Insect Control
Concentrate
Malathion 1 Bonide Malathion Concentrate
Gordon’s Malathion 50% Spray Concentrate
Hi-Yield 55% Malathion Insect Spray Concentrate
Martin’s Malathion 57% Concentrate
Spectracide Malathion 50% Insect Spray Concentrate
Southern Ag Malathion 50% EC
Ortho Max Malathion Insect Spray Concentrate
RTS = Ready to Spray (hose-end applicator)
RTU = Ready to Use (pre-mixed spray bottle)
PHI = Pre-harvest interval or number of days to wait after spraying before harvest.

Pesticides are updated annually. Last updates were done on 5/21 by Joey Williamson.

Originally published 02/99

If this document didn’t answer your questions, please contact HGIC at hgic@clemson.edu or 1-888-656-9988.

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