Beet Webworm
HOSTS
- Beets
- Hemp
- Amaranthus
- Legumes
- Spinach
- Cotton
- Corn
- Eggplant
- Variety of weeds
DESCRIPTION
Larvae are primarily green with light stripes and white spots that contain black centers. Adults are brownish-tan moths that have white markings on their wings.
BIOLOGY
Egg | Larva | Pupa | Adult- 2 generations per year.
- Overwinter as larvae in soil and pupate in late spring.
- Adults emerge in June and females lay egg clusters on the undersides of leaves.
- Larvae disperse and feed on leaves.
- Larvae drop to the ground to pupate in the soil.
DAMAGE SYMPTOMS
Larvae first feed on leaf surfaces, skeletonizing an area the size of its body. As larvae grow, they roll leaflets or pull leaves together with their silk and feed within a leaf tube. Feeding damage can also include irregular holes, visible webbing, and shredded leaves.
GENERAL MANAGEMENT
- Maintain natural enemies.
- Remove weeds and other plant debris surrounding crop.
- Hand-pick and destroy larvae.
- Approved insecticides are available. One option is Bacillus thuringiensis (Bt), which must be consumed, so it should only be used when caterpillars are less than one-half inch in size.
Time for Concern: Mid-summer to late fall.
When and Where to Scout: Adults fly at night and are rarely seen. Look for small egg masses on the undersides of leaves starting in June. Larvae can be found beginning in June to early July.
Threat Level: Low. Foliage damage is minor and should not reduce yields.
Occurrence in Utah: Commonly found in field production feeding on random leaflets. Suspected damage to flower buds,
but not confirmed.