This article expands on the list of garden pests from the first article “Bean Pests” which discusses several garden pests likely to cause damage to bean plants. Damage to plants can be minor or may be devastating to the crop in that damage can be severe enough to kill off the entire crop.
Some of the insects covered below include leafhoppers, root knot nematodes, mites and Mexican bean beetles.
Leaf-miners
Adult leaf-miners are very small yellow and black insects while the larvae are pale green. Larvae tunnel into leaves creating a translucent white trail.
To prevent damage use row covers in early spring. Sticky traps may also be set out in gardens to catch adults before they lay eggs. Search organic garden supply dealers for parasitic nematodes which will attack the larvae once they enter leaves. Damaged leaves should be removed and destroyed.
Mexican Bean Beetle
Adult Mexican bean beetles are yellowish-brown with black spots on their wings, or wing covers. The nymphs of this beetle are orange or yellowish-orange and have tiny spines. Adults lay eggs on the underside of leaves in masses. This beetle can cause a lot of damage in the vegetable garden. It is important to prevent or control it early.
Utilize natural controls such as parasitic wasps (Pediobius foveolatus) released annually. Also, entice *spined soldier bugs (Podisus maculiventris) to the garden. Pyrethrin may also be used.
*See photo below
Mites
Plant mites look like tiny spiders under a microscope. They can be found on the undersides of leaves but will appear as little dark spots among webbing on leaf surface.
Simply shoot them with a stream of water from the garden hose to wash them away. If the problem persists, apply a homemade insecticidal soap to foliage.
Potato Leafhoppers
Adult potato leafhoppers are 1/10” long, green-yellow insects with wings. The young are smaller and do not have wings. When leafhoppers are present, leaves of affected plants will turn yellow and edges will curl. Plants will wilt dropping both blooms and bean pods. This insect also spreads viral diseases from plant to plant.
Use row covers in early spring to protect seedlings. Spraying foliage, especially the undersides of leaves, with an insecticidal soap or pyrethrin is effective if insects are present. Sprays will kill the young leafhoppers but adults will most likely fly away when disturbed.
Root Knot Nematodes
Nematode’s threadlike larvae burrow into plant roots and cause ‘galls’ on roots preventing plants from drawing water and nutrients from the soil. Plants affected will wilt on warm days and perk up again after the sun sets. Plants will also be stunted and turn yellow. Roots with gall will be covered with dark swollen areas.
Pull up and destroy infected plants. Release parasitic nematodes in soil to control infestation.
Tarnished Plant Bugs
Adults are ¼” long, oval-shaped, green to brown. Young bugs are greenish-yellow. Tarnished plant bugs feed on new growth which causes plants to turn yellow and be distorted.
Treat by adding sticky traps to the garden area or spray with pyrethrin in the evening.
Tips
It is preferable to prevent harmful insects in the garden rather than declaring war on them once they have set up house.
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.
For a list of heirloom beans that are making a come-back in gardens today, see the article “Heirloom Beans of Note” and information on bean plant diseases can be found in the article “Bean Diseases.”
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