Pests attack weak bean plants when they’re hungry. A healthy, biodiverse garden protects itself from these insects. When gardens are rich with plants and animals, pest predators, fungi, and bacteria work to bolster your plants’ disease and pest resistance.
Adding compost, avoiding chemical sprays, and using organic gardening methods are three easy ways to increase biodiversity. Adding new perennial and annual species also helps—more plants offer more flowers, inviting insect predators like ladybugs, wasps, and pirate bugs. It also helps to plant many varieties of beans to increase diversity and resilience at the genetic level.
Prevention is the best method for keeping sap-sucking insects out of your garden. They’ll quickly eat your plants and multiply once they find their way onto your beans. These organic removal techniques will banish them so they don’t return, keeping your harvest safe.
We’ll cover how to identify each pest before discovering the best prevention and removal methods. Without further ado, these are seven common bean pests to look for this season.
Bean Leaf Beetle
The beetles eat young plant and pod tissue, removing new growth before they form flowers and beans.
Bean leaf beetles get their names from being voracious leaf eaters. They are most damaging as adults. The beetles eat young plant and pod tissue, removing new growth before they form flowers and beans. They’re most common in the southeastern U.S. in clay soils from spring to summer.
The larvae aren’t as damaging, although they can eat tender roots while they form. These leaf beetles are primary vectors of bean pod mottle and mosaic viruses that kill beans. Keep these beetles away, and you’ll keep these diseases out of your garden.
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 Beetle
These beetles are significant pests that damage agricultural and garden crops.
Mexican bean beetles behave similarly to bean leaf beetles, and prevention and removal techniques for the two are similar. These beetles are more aggressive, creating three to four generations in a single growing season!
Common throughout the U.S. except on the West Coast, Mexican bean beetles are a significant pest that damages agricultural and garden crops. Use prevention techniques annually to keep them at bay, and encourage natural predatory insects to come by bolstering your garden’s biodiversity.
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 Fleahopper
Large populations suck sap from leaves, weakening entire plants and leaving a mottled appearance.
Garden fleahoppers are native insect pests that thrive in the eastern U.S. up through Canada. Although they’re a native species, they cause significant damage to foliage throughout the warm months. They hop away at the first sight of danger, giving them their name “fleahopper.”
Large populations suck sap from bean leaves, weakening entire plants. The weak leaves eventually wither and die, reducing how much photosynthesis your beans can perform. Luckily, garden fleahoppers are native insects, which means they have plenty of common predators that hunt them. Invite them to your garden with wildflowers, shrubs, and flowering trees.
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.
Aphid
A single aphid isn’t a problem, but hundreds of them are.
Aphids attack most ornamental species and our precious crops! They’re small, soft-bodied insects with piercing mouth parts. A single aphid isn’t a problem, but hundreds of them are. They quickly reproduce when happy because young aphids hatch with ready embryos that birth a few days later. They create two generations for the price of one!
Aphids damage your legume crops by eating leaves, stems, and flower buds. You may notice lots of ants around infestations, as they farm these pests to harvest the nectar-like excretions they make.
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 Earworm
You’ll notice small tunneling holes in your bean pods that have black or brown excrement coming out of them.
Corn earworms are nasty little larvae that tunnel into young bean pods. They live in them, damaging beans by eating them and excreting waste into the pods. You’ll notice small tunneling holes in your bean pods that have black or brown excrement coming out of them.
Corn earworms are also called tomato fruitworm because they attack other crops like corn, peppers, and eggplant. You’ll notice the larvae and brown moths fluttering around crops at night from midsummer onwards.
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.
Brown Marmorated Stink Bug
They emerge from late spring through summer, laying eggs and eating leaves, fruits, and flowers.
Some stink bugs are native to North America, while other pests like the brown marmorated stink bug are invasive species from foreign continents. Some overwinter in nooks and crannies in attics, basements, and crawlspaces throughout U.S. homes. They emerge from late spring through summer, laying eggs and eating leaves, fruits, and flowers.
Get down and dirty with your beans to remove these pests. They require some manual picking to remove, but you’ll have help from local birds that feast on these juicy bugs. Marmorated stink bugs move from plant to plant, so you’ll want to reduce their populations before they spread throughout your garden.
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
Control vine weevils with sticky traps or horticultural soap.
A common pest of the southern U.S., cowpea curculio bugs attack beans, peas, strawberries, and other crops. They leave eggs on the insides of bean pods, which then hatch into small grubs. The worm-like grubs eat the maturing peas or beans before exiting into the soil. They pupate and hatch as adult beetles, who repeat the process all over again.
Cowpea curculios threaten maturing harvests from midsummer through fall. Prevent adults from hatching eggs, and you’ll protect your tender pods. Address infestations as you see them since mature beetles can overwinter in rubbish piles, crop refuse, and other protected sites.
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.
Key Takeaways
- Biodiversity, compost, and local animal populations prevent pests from establishing themselves. Use more diverse plant species in your garden, and add compost annually to bolster crop defenses.
- Pests are food for insect predators—beware of synthetic insecticides that may damage other animals further along the food chain.
- Plant pest-resistant varieties in early spring or fall to avoid most pests’ active life cycles.
- If you must use a chemical spray, use an organic one like neem oil or insecticidal soap. They aren’t as harmful as synthetic insecticides.
