Mint XXXI-8

Wireworms

Sue Blodgett & Bill Grey

Wireworm larva.

Identification (life cycle and seasonal history)

Adult beetles are slender, tan to nearly black, and range from 1/2 to 3/4 inch long. Larvae are hard, segmented, measure 1/2 to 1 inch long, and vary from yellow to brown. Wireworms overwinter as larvae or as recently developed adults that do not emerge from the soil until the following spring. Adults disperse by flying within fields or to new fields. Eggs are laid in the soil, hatching with 3-4 weeks.  The larvae move through the soil in search of food.  Larval stages can last for up to 7 years in Montana, depending upon species.

Plant Response and Damage

Larvae, feeding on mint roots, rhizomes and stems are primarily a problem during establishment of a mint stand with serious infestations especially following potatoes, onions, sugarbeets, or grass pastures.

Management Approaches

Wireworm populations can be estimated by taking square foot soil samples to a depth of about 2 to 3 inches around mint plants from several different locations in the field. Usually, wireworm larvae, if present, also will be collected at the same time samples are taken for cutworms, strawberry root weevil, mint root borer, and symphylans. Soil should be screened in the field or placed in Berlese funnels to extract these pests.

No treatment threshold has been developed for wireworms on mint.

Cultural Control

Using mint roots that are certified pest-free to establish new fields is of utmost importance. Some wireworm species may take up to 7 years to complete their life cycle.  Fields with a previous history of wireworms may be fallowed and cultivated to kill weed hosts for 1 year prior to planting mint, but wireworm larvae may continue to be a problem because of the long life cycle of some species.

 Chemical Control

If mint is to be planted in fields with a previous history of wireworm injury, growers should consider fumigating the soil prior to planting mint. Pre-plant fumigation with Telone II, C-17 or C-35 is costly and therefore usually used to control multiple pests.

Categories: Mint, Insects, Wireworms

Date: 06/06/2006