European Corn Borer Moths Observed in Western Illinois

May 26, 2000
Jody Foutch, field sales manager with Novartis Seeds, Carlinville, has established a network of cooperators who have begun to monitor flights of European corn borer moths with pheromone traps. Very light first captures of moths have been reported in Christian (5/13), Macoupin (5/14), Morgan (5/11), and Pike (5/19) counties. Jody also reported an initial capture of European corn borer moths in Jefferson County on May 15. During the evening of May 23, 10 moths were caught by a cooperator in Macoupin County. Recall that Ron Hines, senior research specialist, Dixon Springs Agricultural Center, reported the first captures of European corn borer moths on May 9 in extreme southern Illinois (Pope County). Jody's network of cooperators began to monitor for European corn borers on May 1. So far, the flight has been very light; however, given the wide-scale early planting that occurred this spring, corn borer moths have great targets on which to lay their eggs. In addition, if the weather during the next several weeks is relatively storm free, anticipate above average success in mating and egg deposition.

European corn borer moths (one with extended wings, two with wings not extended).

Entomologists have developed a system to predict the occurrence of different life stages and activity of European corn borers throughout a growing season, based upon the initial capture of moths in the spring. By using May 9 as the first flight date in southern Illinois, we can predict when eggs are likely to hatch and, more importantly, when stalk boring will begin. Robert Scott, Illinois State Water Survey, indicates that from May 9 to May 22, 200 heat units accumulated across the southern one-third of Illinois. When 212 heat units (base 50°F) have accumulated from the first spring flight, we should expect that egg hatch has occurred and first-instar larvae are beginning to create pinholes on corn leaves. Second instars and shot-hole leaf feeding can be found when 318 heat units (base 50°F) have accumulated. Third instars and stalk boring can be observed when 435 heat units (base 50°F) have accumulated. Treatment decisions must be made prior to the stalk-boring event because larvae that have tunneled into stalks cannot be killed with rescue treatments.

The bottom line: egg hatch is under way in southern Illinois, and by late May we should expect the same for central Illinois. Stay tuned for more information on how to scout for the first generation of this insect pest. Even though overwintering populations of European corn borers were at near historic lows, conditions this spring have been favorable for excellent first-generation establishment.--Mike Gray

Author: Mike Gray