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Section 26.6.8: European Corn Borer

Ostrinia nubilalis

Time of concern: Mid-May through September
Key characteristics: Eggs are laid in scale-like masses on the undersides of leaves. The larvae are white to gray with a dark brown head capsule and are 3/4 inch long when fully developed. The adult is a yellowish to reddish brown moth, about one inch in length. In whorl stage, corn damage may appear in leaves as a series of small pin holes perpendicular to the leaf midrib. Small larvae are often found feeding on emerging tassels.  Second brood adults are much less likely to oviposit on whorl stage corn and emerge in the tassel than are first brood adults. Ear feeding can make ears unmarketable. Damage to stems is evidenced by the presence of sawdust-like material in leaf axils and broken tassels and stems.

Management Option Guideline
Scouting/thresholds

Processing sweet corn - monitor the flight activities of adult moths with pheromone traps.  Use degree day models which describe insect development. Critical time periods for the management of ECB are defined by the simultaneous occurrence of: 1) the field is in late whorl/tassel/or silk stage and 2) pheromone trap catches of European corn borer are increasing. If both conditions are met, begin field scouting. Sample 40 plants (five plants at each of eight sites). Inspect all parts of each plant sampled. When two or more egg masses in the black-head stage are found in 40 plants, treatment should be applied two days later or when two or more egg masses without the black-head stage are found in 40 plants, treat three days later. 

Fresh-market sweet corn - sample fields once per week, more often if the temperature is above 80°F. Use the sampling protocol in fields of ten acres or less. If fields are larger, divide them into ten acre blocks and sample each separately. See Reference 3.

Fresh Market Sweet Corn IPM Scouting Procedures

Growth Stage Threshold
Early tassel and tassel 15% infestation
Silk stage through harvest 5% infestation in ear zone

See How to Scout Fresh Market Sweet Corn for specific sampling instructions and scouting form.

The most recent trap catches of the Sweet Corn Pheromone Trap Network are posted and updated each Tuesday during the growing season.

Resistant varieties The only highly resistant varieties available are Bt sweet corn varieties.  Single Bt gene varieties have provided excellent control of ECB and good control of corn earworm (CEW) and fall armyworm (FAW) under typical insect pressure.  Under high pressure, supplemental insecticide sprays for CEW and FAW may be warranted for single gene Bt sweet corn varieties.  Dual Bt gene sweet corn has provided excellent control of ECB, CEW and FAW.
Crop rotation

Crop rotation may be useful if corn follows another crop and is well separated from other corn fields or noncultivated areas having alternate weed hosts.

Natural enemies

A variety of natural enemies help suppress ECB infestations including predatory lady beetles, minute pirate bugs and lacewings, and fly and wasp parasitoids. Use Natural Enemies of Vegetable Insect Pests for identification of natural enemies.

Biological Control of European Corn Borer:
Trichogramma ostriniae, an egg parasitoid, has been recorded suppressing infestations by up to 50% in some cases. Releases of 30,000 per acre should be made when the sweet corn is knee high or slightly before. One release packet per acre is recommended. Insecticides can still be applied following releases if infestations exceed thresholds. This species will not suppress corn earworm or fall armyworm.

NOTE: Predators can substantially reduce the number of ECB eggs. To maximize the effects of these biological agents, use insecticides that will conserve natural enemies. Bt varieties have been effective against ECB while conserving natural enemies.

Postharvest Destruction of corn residue and plowing in the fall can destroy a significant number of overwintering larvae.
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.

Note In recent years, it has been observed that pyrethroids are less effective in the field under high temperatures. Laboratory studies have confirmed this with European corn borer and shown that other classes of insecticides are generally less sensitive to high temperatures. Additionally, high temperatures will shorten the “window of control” for European corn borer.
Pesticides Cornell Integrated Crop and Pest Management Guidelines for Commercial Vegetable Production