University of Maryland Extension

European Corn Borer - Vegetables

European corn borer
Photo credit: Galen Dively, UME

Ostrinia nubilalis (European corn borer)

Back to Common Problems - Vegetables

AppearanceEggs: 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/HabitsOverwinter 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 PlantsCorn.  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/SymptomsBorers 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.
MonitoringFor 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.
Prevention/Control
  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:

larvae bored into fruit
Corn borer larvae

hole in top of green pepper
Corn borer hole in pepper fruit

corn borer entered pepper in stem end
Borers often enter peppers around
the fruit stem and feed on the seed core 

larvae
European corn borer larvae

pinholes and frass made by borer
Damage to stem made by borer activity

egg mass
European corn borer eggmass

Photo credit: Galen Dively, UME

 

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