Bean Pests

Not every garden will be infested with disease-causing insects however; anyone that has gardened for any length of time will no doubt have problems caused by aphids, leaf miners and other bugs which can rob healthy plants of nutrients.

Below is a list of damage-causing insects which can be found in the garden.

Bean Aphids

Aphids are sucking insects responsible for major damage in the vegetable garden. Plants affected by aphids have yellow, withered leaves. Aphids also spread the viral diseases bean mosaic and curly top virus from plant to plant in the garden. The adults are small and black with soft bodies.

If keeping a close watch on the garden, aphids can be spotted before damage occurs. Spray off plants with a stream of water using the garden hose. This will knock the bugs off foliage. For major infestations of aphids use the organic compound pyrethrin (made from Chrysanthemum flowers) to kill bugs.

Bean Leaf Beetles

Adults are about ¼” long, dark yellow or some may be reddish with black dots on their backs and a black band around the outer edges of wings. Larvae are slender white with brown ends and can be up to ½” long. Adults feed on the bottom sides of leaves while larvae feed on roots.

Utilize natural controls such as parasitic wasps (Pediobius foveolatus) released annually and enticing spined soldier bugs (Podisus maculiventris) to the garden. Pyrethrin may also be used.

Bean Weevils

This snout beetle bug presents a problem for stored beans. Adults are brown or gray and small. Larvae are very small and light in color. They tunnel into dry beans with their snout leaving stored beans full of holes.

To prevent damage, place beans in a controlled temperature area of 0° F for up to five days before storing. This will kill the larvae that may be on beans. Heat may also be used to kill larvae by placing beans in oven for up to thirty minutes at 125°.

Cucumber Beetles

These beetles are greenish-yellow with black stripes (Acalymma vittatum) or black spots (Diabrotica undecimpunctata howardi). Adults feed on newly sprouted seedlings and lay eggs in soil near plant roots in early spring. When larvae hatch they feed on plant roots, tunneling holes through them. A second generation of adults feed on blossoms and foliage which may cause low yields of beans. Cucumber beetles are known to transfer bacterial wilt from plant to plant. [1]

Prevent early spring damage by using row covers when seedlings begin to emerge. If an infestation of beetles is apparent, use pyrethrin to kill insects.

Flea Beetles

Flea beetles are small with a shiny black body. They chew tiny holes in leaves leaving behind crisscrossed trails.

Treatment is the same as for cucumber beetles above.

Green Stink Bugs

Possibly one of the most recognizable insects in the garden, the stink bug is a flat green bug shaped like a shield. Young insects have reddish-brown markings. Bean pod damage appears as raised wart-like spots.

Easily controlled by hand-picking and destroying bugs. For severe infestations use pyrethrin spray or dust.

Tips

Preventing infestations rather than treating them after the fact is always preferable.

To accomplish this:

• Plant seeds in healthy soil
• Use row covers in spring.
• Practice good crop rotation habits.
• Do not neglect garden, take regular walks through to check for any new insect activity.

More plant pests can be found in this article, “More Bean Pests.” For a list of heirloom beans that are making a come-back in gardens today, see the article ‚”Heirloom Beans of Note” and for information on bean plant diseases see the article ‚”Bean Diseases.“

Sources:

[1] Virginia Cooperative Extension “Cucumber Beetles” Eric Day, Manager, Insect Identification Laboratory Publication 444-222, August 1996