Soil Insect Pests of Vegetables

Pest Management Fact Sheet #5045

James F. Dill, Pest Management Specialist
Clay A. Kirby, Insect Diagnostician

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Description & Biology

The following are the most significant soil insects attacking home garden plants.

Wireworms are the immature stage (larva) of the click beetle. Wireworms are cylindrical, about 1-1/2 inches long, brownish to yellow and are rather hard-bodied. These insects eat seeds, cut into small shoots and often bore into stems, roots, and tubers. They attack many vegetables including potatoes, onion, corn, carrots, peas, beans, and melons.

White grubs are cream colored, C-shaped larvae with brown heads. They include the immature stage of European chafer, Japanese beetle, and beetles from the genus Phyllophaga (May beetles/June bugs). They stay in the soil and feed on the roots of corn, beans, peas and other vegetables. They are most likely to damage plants in or near ground that was recently sod covered.

Cutworm Feeding on Potato Stem
Cutworm Feeding on Potato Stem

Cutworms are the larval, or immature, stage of certain moths. They can often destroy a stand of plants in a garden. Cutworms are night feeders and are seldom seen during the day. These insects cut off small plants at or near the ground level and feed on the tender stem. Some types climb up the stem and feed on foliage.  Many plants are attacked by cutworms, but they are especially damaging to corn, beans, tomatoes and peppers.

Seed corn maggots are the larvae of small flies. They develop in the soil and feed on seed and seedlings of corn, beans, peas, potatoes, cabbage, melons and other crops.  Cool wet springs and soil with a high concentration of organic matter favor the development of this pest. (No pictures available at this time).

Cabbage Maggots and Pupae
Cabbage Maggots and Pupae

Cabbage maggots are also the larvae of small flies. They feed on fine roots, eventually tunneling into the taproot. They attack cabbage, broccoli, turnips and similar crops. Other maggots which attack vegetable crops are the carrot rust fly and the onion maggot.

Management

Beneficial nematodes can be used for controlling the soil dwelling larval stages of the above pests. Cardboard plant collars, Spinosad, Bt (Bacillus thuringiensis), and carbaryl (Sevin) sprays and baits can be used to control cutworms. Row cover can be used to prevent maggot problems.


When Using Pesticides

ALWAYS FOLLOW LABEL DIRECTIONS!

Pest Management Unit
Cooperative Extension Diagnostic and Research Laboratory
17 Godfrey Drive, Orono, ME 04473-1295
1.800.287.0279 (in Maine)


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