European Corn Borer - Vegetables

European corn borer

Photo credit: Galen Dively, UME

Ostrinia nubilalis (European corn borer)

Back to Common Problems - Vegetables

Appearance Eggs: Oval, flattened, white, usually iridescent, overlapping like fish scales, in large clusters on leaf undersides. Darken somewhat with age.
Larvae: Up to 1" long, pale pink or brownish-gray, hairless caterpillars with brown head and side stripe and black dots on each section.
Pupae: Red-brown, narrowing to a point at posterior.
Adult: 1" moth.  Females pale yellow to brown, males darker with even darker markings.
Life Cycle/Habits Overwinter in stalks as mature larvae. In spring, pupate and emerge as moths.  Egg-laying occurs in May-June and again in July-August on leaf undersides.  Larvae feed on leaves and developing corn tassels. As tassels emerge, larvae bore into stalk or husk at ear tip, side, or base. Usually 2-3 generations a year. Overwinter in stalks. Usually 2-3 generations a year. 
Host Plants Corn.  Can be significant pest on pepper fruit. Secondary pest on foliage or fruit of beans, celery, cowpea, potato, rhubarb, spinach, and tomato, among others.
Signs/Symptoms Borers make pinhole entrances, exuding sawdust-like frass. Foliage above bored stems may wilt or break. Borers enter peppers near the stem and feed on seed core. In young corn shoots, feeding occurs in the central whorl of leaves and silk. Older larvae do the most damage, on sweet corn boring into and feeding primarily in the ear and introducing fungi. Ears will have chewed tips and kernels, with tunneling along rows of kernels and into the cob.
Monitoring For young corn plants, inspect leaves for eggs masses.  Later look carefully into the whorl for developing larvae. Pinhole entrance holes will be visible on stalks and fruit or corn husks.
  1. Manage corn borers by destroying stalks, the overwintering site of larvae. Cut off stalks close to soil. Till under, shred, or remove stalks from the area.
  2. B.t., an "organic" microbial insecticide can be sprayed when larvae first appear.
  3. You can split infested stalks below the borer holes, and then destroy this pest by poking it with a piece of wire or a nail.  

Photo Gallery:

Corn borer larvae

Corn borer hole in pepper fruit

They usually enter peppers around the fruit stem and feed on the seed core

European corn borer larvae

One will notice pinholes surrounded
by sawdust-like frass (caterpillar excrement)

European corn borer eggmass.
Photo credit: Galen Dively, UME


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