Potatoes, carrots, onions and beets are a few of the vegetable crops damaged by wireworms. Here’s how to control them using proven organic techniques.
Common in home gardens across North America, wireworms (up to 1-1/2 inch long) are tough slender worms with shiny skin and three pairs of legs just behind their head. They are yellow to brownish-red in color and feed entirely underground, attacking germinating seeds, roots, bulbs and tubers. Damaged plants soon wilt and die. If infestations are heavy, thin and patchy crops may appear in the garden and reseeding will most likely be necessary.
Note: Wireworms are the larval stage of click beetles. Approximately 1/2 inch long, these brown to black colored, bullet-shaped beetles are notable for their ability to click and right themselves when placed on their backs.
Wireworm larvae and adults overwinter in the soil. In early spring female beetles emerge from the soil, mate and lay eggs underground. Hatching takes place in 2-4 weeks, and the young larvae begin working their way through the soil in search of food. Larvae feed underground for 2-6 years with most of their damage occurring in early spring when soil temperatures are cool. Pupation occurs in late summer and adult beetles emerge in the spring. One generation per year, the life-cycle requiring 1-6 years to complete.
Thorough cultivation makes conditions unfavorable to the egg laying adults and exposes all stages of the pest to weather and natural enemies. Potatoes make great wireworm traps. Cut a potato in half and run a stick through the middle. Bury the spud about one inch deep so that the stick stands vertically as a handle. Pull the traps out after a day or two and discard wireworms. Apply beneficial nematodes when planting to attack and destroy insect pests in the soil. Pyrethrin drenches are also recommended, but should only be used as a last resort.
Tip: If possible, wait until the soil has warmed before planting tubers. Larvae prefer cool soils and dig deeper into the ground when temperatures rise.