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Section 26.6.7: Western Corn Rootworm

Diabrotica virgifera virgifera

Time of concern: Mid-May - Mid-July, larvae; July-September, adults.
Key characteristics: The adult beetles are yellow and brown with yellow stripes on their wings. Adults feed on leaves, tassels, and silks; larvae feed on roots. The larvae are 1/4 inch long when full grown and white with a brown head and "tail.

Management Option Guideline
Scouting/thresholds

Adults and root damage - In mid- and late-season fields check 100 plants (avoid field edges). If the average infestation is ≥1 beetle per plant, then do not plant corn in that field the subsequent year. Another option is to use the sequential sampling program and treatment guidelines for field corn which is available in Sampling and Management of Corn Rootworm in New York Field Corn.  If rotation away from corn is not possible, treat with an insecticide at planting the next year. 

Silk clipping - Silk clipping by adults can reduce ear fill. In field corn, an insecticide treatment is recommended if ≥10 beetles are recorded per plant before pollination has occurred.

Fresh Market Sweet Corn IPM Scouting Procedures

Natural enemies

Naturally-occurring predators, parasitoids, and pathogens help suppress infestations. Use Natural Enemies of Vegetable Insect Pests for identification of natural enemies.

Resistant varieties Varieties with larger root mass tolerate larval infestations better.
Crop rotation

Rotating away from corn for one year is an effective management option. However, since they will also lay their eggs in cucurbit fields, there is a higher risk if corn is planted after cucurbits..

Site selection/planting Late-season planting will decrease the risk of damage from overwintering populations .
Note(s) Insecticide treatments for caterpillar pests generally control adult corn rootworms.
Insecticide Resistance Management

The Insecticide Resistance Action Committee (IRAC) has classified insecticides into resistance management groups. Most insecticides include an IRAC group number on the front page of the label. Alternating between insecticides with different group numbers will help avoid the development of resistant insect populations.

Postharvest and
Sanitation
These are not currently viable management options.
Pesticides Cornell Integrated Crop and Pest Management Guidelines for Commercial Vegetable Production