Purdue News

February 5, 1999 Low European corn borers predicted for 1999 WEST LAFAYETTE, Ind. -- Record low numbers of overwintering European corn borers have been reported in Purdue University's latest survey, indicating a relatively small immediate threat to 1999 crops. This projection of a low corn borer population may play a big part in producers' decisions whether to invest in biotechnology-enhanced seed corn this spring, according to Purdue agricultural economists. Although this year's observations indicated the lowest number of overwintering corn borers since surveys began in 1961, Purdue entomologist John Obermeyer cautioned that these predictions are not foolproof, because environmental factors play the biggest role in determining the economic threat of such a pest. During most growing seasons, two generations of corn borers infest fields; if environmental conditions are favorable, there may be a third generation. "Warm, moist evenings create ideal conditions for the European corn borer moths to be out flying, mating and laying eggs," Obermeyer said. He said extreme weather can severely limit their capacity to infest and damage corn, even though the adult moth does not directly damage the crop. "The damaging stage of the European corn borer is the larval stage, which is a caterpillar," Obermeyer said. "This larva feeds on the leaves of the corn plant and does the most damage by boring into the stalk, which creates a cavity. This can cause the entire corn stalk to fall over, or it can cause part of the plant to fall off, such as the corn ear." Favorable environmental conditions can spell big trouble for corn growers because of the corn borer's ability to multiply and disperse in a relatively short period of time. Given optimal conditions, each adult female moth can produce more than 400 young spread out over many plants and fields. The state survey indicates that economically damaging levels of first-generation European corn borer will be present in 10.3 percent of corn fields, and that number jumps to 25.4 percent for the second generation. Scientists estimate that farmers can lose an average of $6.50 per acre to an infestation of first-generation corn borers and $13 per acre to second-generation borers. At 80 million corn acres nationwide, second-generation corn borers alone threaten to cost U.S. corn farmers more that $1 billion. Predictions of low corn borer levels, at least into the early part of the corn-growing season, give farmers something to think about when it comes to selecting spring seed. Purdue entomologists estimate that because of the low number of overwintering larvae, the number of mating adults should also be relatively low this spring, at least through the first generation. That means early planted corn will likely be subjected to low corn borer numbers. Because the risk of corn borer infestation is low in early planted corn, the extra cost for Bt corn seed probably won't be recovered in this early generation, even in areas of traditionally high corn borer infestation, according to Marshall Martin, a Purdue agricultural economist. Bt corn has been genetically engineered to produce the bacteria Bacillus thuringiensis, which kills corn borers. Martin said economic estimates indicate that early planted Bt corn is expected to return about $5.40 per acre under projected conditions -- well below the current $8 technology fee, which is the premium that growers pay to buy the enhanced seed. However, investing in Bt corn may pay off for producers with late-planted fields or late-maturing corn. Martin said that although it is difficult to predict second- or third-generation populations and damage of corn borers, current estimates are that late-planted fields of Bt corn will experience economic returns between $8.30 and $8.90 per acre on average. For more information on the potential problems of European corn borers in 1999, call Purdue University Cooperative Extension Service at 1-888-EXT-INFO. Sources: John Obermeyer, (765) 494-2152; e-mail, obe@purdue.edu Marshall Martin, (765) 494-4268; e-mail, martin@agecon.purdue.edu Writer: Jane Houin, (765) 423-2890; e-mail, news_students@aes.purdue.edu Purdue News Service: (765) 494-2096; e-mail, purduenews@purdue.edu To the Purdue News and Photos Page