Wireworms

Onion root maggot adult
Appearance
- The larvae are cream colored, legless and 1/3 inch long. They cause the plant damage.
- Adults are flies which lay eggs on plants.
Life Cycle/Habits
- Corn seed maggot, onion root maggot, and wireworms cause similar problems.
- Adult flies emerge in spring and mated females lay eggs at the base of plants. Larvae hatch and tunnel into stems and enlarging bulbs.
- Larvae hatch and tunnel into stems and enlarging bulbs.
- Larvae pupate in the soil near infested plants.
- There are 2-3 generations per year.
Host Plants
- This is a common pest of allium family members.
- Shallots are most vulnerable followed by onions and garlic.
Signs/Symptoms
- Infested plants wilt or turn yellow and die.
- A single larva can damage several plants.
Prevention/Control
- Where this insect has been a problem, use floating row cover to prevent adult flies from depositing eggs.
- Pull and destroy affected plants.
- Keep weeds down to eliminate habitat for adult flies.
- Remove all plant debris and till the garden in the fall to expose and destroy over-wintering pupae.
- Rotate alliums with unrelated crops to reduce insect problems.
- Avoid adding fresh manure to the garden.
Wireworms

Potato wireworm
Appearance
- They are slender, shiny, tough-skinned worms with pale yellow to reddish-brown bodies.
- Wireworms can grow to over 1 inch in length.
- The adults are click beetles.

Click beetle
Photo: Joseph Berger, Bugwood.org
Life Cycle/Habits
- The larvae spend 1-6 years in the soil.
Host Plants
- Potatoes and beet roots. They also infest sweet potato, turnip, and onion.
Signs/Symptoms
- They make many small holes in tubers and beet roots.
- Fresh holes have ragged edges and contain chewed root tissue.
- Wireworms can damage potato seed pieces, opening them to fungal and bacterial infections that result in weak plants.
- They bore into developing tubers, leaving round holes about 1/8 inch in diameter and making the tuber look like it has been punctured with a nail.
- The tunnels may be shallow or deep and go straight into the tuber.
- Injury is more noticeable late in the season, during dry seasons and where turfgrass was recently converted to a vegetable garden.

Potato with a hole made by a wireworm

Potato damage caused by wireworms
Prevention/Control
- Rotate susceptible crops.
- Till garden soil prior to planting in spring to kill and disrupt larvae.
- Plan to dig and eat new potatoes rather than growing storage potatoes.
- To reduce wireworm populations, spear pieces of potato or carrot on a stick and bury them 2 to 4 inches deep in the garden. Dig up the pieces after a week and destroy them, along with the wireworms that are feeding inside. Set the potato traps at 3 to 10 foot intervals.
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