7 Common Bean Pests to Look For This Season

Bean leaf beetle adults are smaller than a quarter inch long, with various patterns and colors on their backs. Most have black spots on yellow-reddish to brown-colored wing covers. They have a black triangle below their head that distinguishes them from other patterned beetles. The larvae look like small white worms with brown ends. You won’t see them above ground. They have six short legs on their front end.

This pest thrives under warm temperatures and is relatively dormant during fall and early spring. Grow early maturing bean varieties during these seasons for damage-free leaves and pods. Late plantings are also a deterrent, as any overwintered beetles move on before beans begin growing. Bean leaf beetles overwinter in plant residue, so removing leftover plants in autumn keeps them from returning in spring.

Kick these beetles out of your garden by spraying them with strong streams of water from a hose or handheld sprayer. Repeatedly knock them off your plants until their populations decline. The wasp Pediobius foveolatus is a predatory insect that eats them, working hard so you don’t have to. They’ll attack larvae and pupa, killing the beetles before they can harm your plants.

Mexican bean beetles are bigger than bean leaf beetles, spanning from two to three-eighths of an inch long. They resemble ladybugs but with a dark orange color. Their black spots form three symmetrical rows across their wing covers.

Keep these beetles out of your garden by planting resilient bean varieties like ‘Wade,’ ‘Logan,’ and ‘Black Valentine.’ Early maturing varieties also mature pest-free, as the beans form before the beetles wake up in spring. Grow this crop in the fall with early maturing varieties for an extra, pest-free harvest. At the season’s end, remove bean plant residue from your garden to prevent beetles from overwintering.

Once they establish themselves these beetles are difficult to remove. They lay orange-yellow eggs in clusters on leaf undersides, which you can smush, wash, or prune off. The predatory wasp Pediobius foveolatus attacks beetle larvae, providing an extra layer of defense. If you see lots of larvae and adults on your beans, hose them off with strong streams of water daily.

Garden fleahoppers are tiny black hopping bugs. The male hoppers are slender and thin, while the females are wide with short or long wings. They each have elongated hind legs that give them a boost when they jump. The nymphs, or young adults, resemble adults but are green or yellow. Adult fleahoppers never grow larger than a sixteenth of an inch long.

Many North American parasitic wasps prey on garden fleahoppers. If you see wasps in your garden, don’t damage them! They will not sting, and you can encourage them to stay with plantings, or leave them be. Further discourage fleahoppers by growing strong, healthy plants with thick layers of compost over their roots. These prevention techniques also work for a similar pest, the potato leafhopper.

If you spot garden fleahoppers, it’s best to leave them be unless they’re excessively harming your crops. Spraying insecticides harms parasitic wasps that prey on these pests. If you must spray, use an organic one like neem oil, water, and insecticidal soap. Apply it in the morning or afternoon while pollinators are dormant. A light mist is plenty.

Many aphid species exist with different colors and markings. Most are around an eighth of an inch long with almond-shaped fleshy bodies. Bean aphids are black bodied insects. They’re often squishy. In heavy infestations, you’ll notice winged, small aphids and wingless wide-bodied ones. They tend to congregate on bean leaf stems and leaf undersides. Look for congregations of black insects when scouting for bean aphids.

Prevent aphids by planting lots of diverse plant species. They’ll cover the soil and preserve moisture while their flowers invite pollinators and predatory insects to the site. Consistent water moisture keeps your plants turgid and strong, preventing aphids from puncturing them. Apply thick layers of compost annually and you’ll further bolster bean defenses. Don’t overfertilize. This will increase plant sugars, attracting aphids.

Remove aphids with the strong hose stream trick. Simply spray water on them until they fall off your beans. With daily sprayings, aphid populations quickly decline and disappear. Ladybugs, wasps, and lacewings are their natural predators, so boost your garden’s biodiversity to invite more of them in.

Corn earworms are worm-like larvae with segments, and they range in color depending on their current life cycle stage. Young earworms are light yellow or brown, maturing to a creamy yellow-green shade. Mature larvae are brown or black with a single dark line down their backside. Adult moths are fuzzy and light brown with a wingspan between one to one and a half inches long.

Prevent corn earworm adults from laying eggs by placing row cover or mesh linings over your beans at night. If eggs hatch this year and you notice damaged bean pods, dispose of them away from your garden. Prevent overwintering earworms by cutting bean plants at their base and removing them from your garden beds at the growing season’s end.

Remove corn earworms by cutting off infected pods, leaves, and stems. Remove as many larvae as possible to prevent them from returning next year, then add mesh liners over your beans at night. Bt is another effective control, especially in a large infestation. These three techniques will remove earworms from your garden and prevent them from spreading further.

All stink bugs have shield-shaped bodies with two antennae sticking out of their lance-shaped heads. Some are slender, like the leaffooted stink bugs, while others like the brown marmorated stink bug are wide and oblong. They form clusters, so you may notice more than one on your bean pods and leaves.

Prevent stink bug infestations by promoting biodiversity throughout your yard. The more wildflowers, trees, and shrubs you grow, the more spaces exist for birds, mammals, and insects to live. Birds love eating stink bugs, and they’ll remove adults from your beans as they see them. Avoid spraying synthetic pesticides on them to avoid harming hungry songbirds. A plant protector, like a shade cloth or frost cloth is a good deterrent but blocks bird access to the bugs.

If infestations grow out of control, some simple manual methods remove them quickly. Grab a bucket and fill it with soap and water. Then, scour over your plants in search of adult stink bugs and their green, round eggs. Smush the eggs; they’ll be on leaf undersides, stems, and forming pods. Take adult stink bugs and throw them in the soapy water. With daily pickings, the pests will disappear within one to two weeks.

Cowpea curculio beetles have dome-shaped bodies with dimpled copper spots. Their grubs are tiny, white worms with two jaws on their front end. You’ll find beetles on leaves, stems, and pods, while larvae live mostly inside soft bean and pea seeds. Their eggs are translucent after adults lay them. They mature to a whitish color before hatching.

Banish cowpea curculios with tidy gardening practices, and by inviting wild birds or chickens to the growing site. Birds eat beetles as they appear, preventing them from laying eggs inside your tender bean pods. At season’s end, remove all bean plant residue and throw it in a hot compost pile to destroy any overwintering adults. Rotate legume crops to ensure lower populations next season.

Cowpea curculios like to play dead, dropping below the stalks when you disturb them. Put a bucket or cardboard box below your beans, then shake them so the beetles fall below. Once they’re in the box, throw them in a bucket of soapy water to kill them. Remove any pods with noticeable damage to prevent the larvae from hatching into the soil.