European corn borer, Ostrinia nubilalis (Hübner), is an economic pest on a wide variety of field adn vegetable crops including corn (field, sweet, & popcorn), snap beans, peppers, potatoes, cotton, and several other vegetable crops. Since its introduction into North America from Europe in the early 1900s, European corn borer has spread to all but seven of the western most states and throughout much of Canada. The wide host range and broad dispersal of this pest contribute to the estimated 1 billion dollars lost annually by U. S. corn growers though decreased yield and control costs.
European corn borers survive winter as diapausing larvae within plant debris near the soil surface. In spring, larvae pupate, and emerge as adults. European corn borer adults are found primarily outside of corn fields, in areas of dense vegetation termed "action sites". Action sites most frequently include grass and weed vegetation adjacent to fields and fence rows, as well as alfalfa, soybean or snap bean fields. In addition, weedy areas within fields, such as waterways and wheel tracks, can serve as effective action sites. European corn borer aggregate in action sites because the heavy vegetation provides ideal conditions for resting, mating and water for adult feeding.
European corn borer are active at night, and the formation of dew on warm, calm evenings provides ideal conditions for moth survival and egg production. Female moths will usually not mate until about 2 dayes after emergence. Mated females move into fields to lay eggs with each female usually laying two egg masses of 15 to 30 eggs per night for 7 to 10 nights. Egg masses are typically laid on the underside of the leaves near the midrib. Female moths disperse significant distances to find favorable fields. Corn is the preferred host and female moths select the tallest corn during the first flight, and corn at pollen-shed and early silk during late-season flights. If corn is not present or in the brown silk stage, European corn borer will lay eggs on a variety of succulent alternative hosts (e.g., peppers or snap beans).
In Minnesota, the first generation flight typically occurs around June 1st, followed by a second flight in early August (see graph). The number of generations per year varies with location. In northern Minnesota and Canada European corn borer typically completes only one generation, while 3-4 generations per year routinely occur in southern states.
Sweet corn -
Field corn -
Snap beans -
Peppers -
ECB feeding results in poor ear development, dropped ears, and broken stalks. This damage is caused by ECB:
The boring and feeding behavior of ECB larvae require precise timing of the use of insecticides. Only a narrow window of time is available when larvae are vulnerable to foliar insecticides. To achieve acceptable levels of control, insecticide applications should be made at the onset of egg lay to ensure that the insecticide will be present as larvae move from the egg mass to feeding sites. Proper timing of insecticide applications is difficult because of current monitoring technology. Black-light traps are the most reliable method to monitor adults; however, the traps require a power source, and are not species specific, making identification and sorting of insects difficult. However, in some states,such as Minnesota, light-trap networks have been established to provide timely updates on moth flights. and time consuming.
Traditionally, pheromone trapping systems have not provided consistent results (Mason 1996). Although, recent research in Minnesota has shown that European corn borer pheromone lures can be effective when prepared properly (maintain quality control), it has been difficult to find consistent sources of pheromone lure for ECB in the midwestern U.S. The most reliable method to determining egg lay in the filed is to scout corn fields for egg masses. However, scouting is also very time consuming and expensive because of the effort required. For these reasons, many growers do not apply insecticides or spray on a calendar schedule.
Authors: David Bartels and W. D
Hutchison
Revised: July 15, 2002.
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