Soil Insect Pests of Vegetables
Pest Management Fact Sheet #5045
James F. Dill, Pest Management Specialist
Clay A. Kirby, Insect Diagnostician
Charles D. Armstrong, Cranberry Professional & Staff Entomologist
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Description & Biology
The most significant soil insects attacking home garden plants in Maine are:
- Wireworms – these are the immature stage (larva) of the click beetle. Wireworms are cylindrical, about 1½ 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, onions, corn, carrots, peas, beans, and melons.
- White grubs — “White grubs” are a group of beetle larvae (Family Scarabaeidae) that are cream-colored and C-shaped 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.
- 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 the foliage. Many plants are attacked by cutworms, but they are especially damaging to corn, beans, tomatoes and peppers.
- Cabbage maggots (Delia radicum) are the larvae of small flies in a family of root-maggot flies called Anthomyiidae. They feed on fine roots, eventually tunneling into the taproot. They attack cabbage, broccoli, turnips and similar crops. Other maggots which attack vegetable crops include the carrot rust fly and the onion maggot.
- Seedcorn maggots (Delia platura) are the larvae of another species of fly in the Anthomyiidae family. They develop in the soil and feed on seed and seedlings of corn, beans, peas, potatoes, cabbages, melons and other crops. Cool wet springs and soils with a high concentration of organic matter favor the development of this pest. (No pictures available of this pest as yet.)
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 covers 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
1.800.287.0279 (in Maine)
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