Category : Insects
Aphids (Cowpea aphid, Pea aphid, etc.)
Cowpea aphid (Aphis craccivora) infestation
Black Bean Aphid Aphis fabae
Winged aphids, the vectors of Bean Common Mosaic Virus (BCMV), on a bean leaflet.
Aphids on lower surface of leaves
Ladybird beetle feeding on bean black aphids
Aphid infestation on bean plant
Close-up of Black Bean Aphids (Aphis fabae) colony
The aphids are tended by ants
Small soft bodied insects on underside of leaves and/or stems of plant; usually green or yellow in color, but may be pink, brown, red or black depending on species and host plant; if aphid infestation is heavy it may cause leaves to yellow and/or distorted, necrotic spots on leaves and/or stunted shoots; aphids secrete a sticky, sugary substance called honeydew which encourages the growth of sooty mold on the plants.
If aphid population is limited to just a few leaves or shoots then the infestation can be pruned out to provide control; check transplants for aphids before planting; use tolerant varieties if available; reflective mulches such as silver colored plastic can deter aphids from feeding on plants; sturdy plants can be sprayed with a strong jet of water to knock aphids from leaves; insecticides are generally only required to treat aphids if the infestation is very high - plants generally tolerate low and medium level infestation; insecticidal soaps or oils such as neem or canola oil are usually the best method of control; always check the labels of the products for specific usage guidelines prior to use.
Armyworms (Beet armyworm, Western striped armyworm)
Adult of beet armyworm
Beet armyworm adult
Damage due to early stage beet army worm larvae
Beet armyworm (Spodoptera exigua) egg mass covered with hairs.
Beet armyworm egg mass hatching
Beet armyworm eggs
Larvae of beet armyworm
Beet army worm late instar larvae
Beet armyworm (Spodoptera exigua) on leaf
Singular, or closely grouped circular to irregularly shaped holes in foliage; heavy feeding by young larvae leads to skeletonized leaves; shallow, dry wounds on fruit; egg clusters of 50-150 eggs may be present on the leaves; egg clusters are covered in a whitish scale which gives the cluster a cottony or fuzzy appearance; young larvae are pale green to yellow in color while older larvae are generally darker green with a dark and light line running along the side of their body and a pink or yellow underside.
Organic methods of controlling armyworms include biological control by natural enemies which parasitize the larvae and the application of Bacillus thuringiensis; there are chemicals available for commercial control but many that are available for the home garden do not provide adequate control of the larvae.
Adult and larvae
Larvae feeding on leaf
Corn earworm (Helicoverpa zea) adults
Corn earworm on bean
Larvae damage leaves, buds, flowers, pods and beans; young caterpillars are cream-white in color with a black head and black hairs; older larvae may be yellow-green to almost black in color with fine white lines along their body and black spots at the base of hairs; eggs are laid singly on both upper and lower leaf surfaces and are initially creamy white but develop a brown-red ring after 24 hours and darken prior to hatching.
Monitor plants for eggs and young larvae and also natural enemies that could be damaged by chemicals; Bacillus thuringiensis or Entrust SC may be applied to control insects on organically grown plants; appropriate chemical treatment may be required for control in commercial plantations.
French beans attacked by Helicoverpa armigera. Note the larvae within the bean.
Cutworm damage to bean seedling
Cutworm larva severing plant stem
Bean leaf skeletonizer (Autoplusia egena) larva
Cutworm feeding on plant stem
Eggs of western bean cutworm (Striacosta albicosta)
Cutworms will curl up into a characteristic C shape when disturbed
Stems of young transplants or seedlings may be severed at soil line; if infection occurs later, irregular holes are eaten into the surface of fruits; larvae causing the damage are usually active at night and hide during the day in the soil at the base of the plants or in plant debris of toppled plant; larvae are 2.5–5.0 cm (1–2 in) in length; larvae may exhibit a variety of patterns and coloration but will usually curl up into a C-shape when disturbed.
Remove all plant residue from soil after harvest or at least two weeks before planting, this is especially important if the previous crop was another host such as alfalfa, beans or a leguminous cover crop; plastic or foil collars fitted around plant stems to cover the bottom 3 inches above the soil line and extending a couple of inches into the soil can prevent larvae severing plants; hand-pick larvae after dark; spread diatomaceous earth around the base of the plants (this creates a sharp barrier that will cut the insects if they try and crawl over it); apply appropriate insecticides to infested areas of garden or field if not growing organically.
Larvae of leafminer
leafminer fly (Liriomyza sp.) adult
An infested common bean leaf showing tracts of the leaf miner Liriomyza sp.
Tunnels caused by leafminer
Leafminer damage on bean plant leaf
leafminer fly (Liriomyza sp.) pupa
vegetable leafminer (Liriomyza sativae) adult
vegetable leafminer (Liriomyza sativae) on bean leaves
Thin, white, winding trails on leaves; heavy mining can result in white blotches on leaves and leaves dropping from the plant prematurely; early infestation can cause fruit yield to be reduced; adult leafminer is a small black and yellow fly which lays its eggs in the leaf; larvae hatch and feed on leaf interior.
Check transplants for signs of leafminer damage prior to planting; remove plants from soil immediately after harvest; only use insecticides when leafminer damage has been identified as unnecessary spraying will also reduce populations of their natural enemies.
Loopers (Cabbage looper, Alfalfa looper)
soybean looper (Thysanoplusia orichalcea) on dry beans
Looper on bean leaf
Large or small holes in leaves; damage often extensive; caterpillars are pale green with a white lines running down either side of their body; caterpillars are easily distinguished by the way they arch their body when moving; eggs are laid singly, usually on the lower leaf surface close to the leaf margin, and are white or pale green in color.
Looper populations are usually held in check by natural enemies; if they do become problematic larvae can be hand-picked from the plants; an organically acceptable control method is the application of Bacillus thuringiensis which effectively kills younger larvae; chemical sprays may damage populations of natural enemies and should and should be selected carefully.
Mexican bean beetle
Adult beetle and damage to bean foliage
Eggs laid on underside of bean leaf
Adult Mexican bean beetle
Bean plant infested with Mexican bean beetle larvae
Mexican bean beetle larva
Mexican bean beetle damage to bean foliage
Irregular patches of feeding damage on underside of leaves which causes the top surface of the leaf to dry out, giving the leaves a lacy appearance; insect will also damage flowers and small pods; pods may be damaged so badly that they drop from the plant; adult insect is an orange-brown beetle with black spots; larvae are fat-bodied grubs which taper at the end and are in rows of conspicuous spines
Some bean varieties may be less attractive hosts for the beetle, e.g. snapbeans are preferred hosts over lima beans; early varieties may escape damage form beetles beetle populations can be reduced by remove overwintering sites such as brush and leaves on the ground; handpick larvae and adults; brush eggs from leaves and destroy; apply insecticidal soap to leaf undersides if infestation is heavy
Stinkbugs (Consperse stinkbug, etc.)
brown stink bug (Euschistus servus) eggs
Stinkbug feeding on bean pod
Predaceous anchor stink bug (Stiretrus anchorago) attacking green stinkbug nymph.
Florida Preatory Stink Bug, Euthyrhynchus floridanus (beneficial insect)
Southern stinkbug feeding on bean leaf
Globular stinkbug on leaf
Stinkbugs infestation on bean leaves
Dark colored pinpricks on fruit surrounded by a lighter area that turns yellow or remains light green; stink bugs often carry pathogens in their mouthparts which can cause secondary infections and decay of fruit; adult insect is shield-shaped and brown or green in color; may have pink, red or yellow markings; eggs are drum shaped and laid in clusters on the leaves; larvae resemble the adults but are smaller.
Remove weeds around crop which may act as overwintering sites for stink bugs and practice good weed management throughout the year; organically accepted control methods include the use of insecticidal soaps, kaolin clay and preservation of natural enemies; chemical treatments are not recommended for tomatoes that are to be processed for paste or canning unless secondary infections with other pathogens are a concern.