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Issue No. 12, Article 1/June 13, 2008

Still No Widespread Issues with Insects in Field Crops

Extension field crop entomologists in the north central region participated in a teleconference on June 9, and most state reports had the same theme: not much happening insect-wise. The history-making wet weather is dominating conversations and media discussions focused on agriculture, and under the circumstances, insects rank fairly low on the list of concerns. Following are capsule reports on insects deserving some attention, including some reports of "firsts" for 2008.

Armyworms in wheat. Entomologists in Indiana and Ohio indicate that armyworms in wheat may be the "biggest insect story" in their respective states, but they also indicated that economic problems are not widespread. We recently received a couple of reports of armyworms feeding on flag leaves or otherwise present in wheat. The reports were from Illinois counties in the south (refer to Ron Hines's June 10 comments in "The Hines Report,") and west-southwest (Lisa Coorts, Maxi-Yield Consultant Service, Carlinville). Feeding by armyworms on flag leaves and on the peduncle below the head can result in significant yield losses if infestations of the caterpillars are heavy.

Bean leaf beetles in seedling soybeans. Reports of bean leaf beetles feeding on seedling soybeans are scattered throughout the Midwest, although there have been few reports of significant feeding injury. Remember that the earliest planted fields are most likely to be noticeably infested by the beetles that have emerged from hibernation quarters this spring. Also remember, however, that economic damage usually does not occur unless densities of bean leaf beetles are high. Current commodity prices and stress on the young plants justify some tinkering with economic thresholds, but reason should prevail.

Black cutworms in corn. The most prevalent insect problem this spring has been black cutworms feeding on seedling corn, but we have fallen far short of a widespread outbreak. Nonetheless, recently planted corn or corn in fields that will be replanted will be vulnerable to black cutworms for a while. We have written several articles about black cutworms and their management in previous issues of the Bulletin this year (e.g., issue No. 9, May 23, 2008).

European corn borer adults. Several people throughout the Midwest have reported the first captures of European corn borer adults in traps this spring, so we know the flight of females that will lay eggs to initiate the first generation is underway. Remember that these females will seek taller cornfields for laying eggs, and larvae will not survive well on smaller corn plants.

Japanese beetle. Ron Hines (FS seed agronomist, southern region, Growmark) reported the first Japanese beetles of the season captured in a trap in Franklin County on June 10. In "The Hines Report," Ron indicated that this first capture in 2008 is approximately 10 days later than the first capture in 2007. We will have to observe carefully as Japanese beetles continue to emerge and begin seeking food. Pollinating corn (can we imagine that yet?) and flowering soybeans will be at risk if lots of Japanese beetles survived the winter temperatures and this spring's excessive rains.

Soybean aphids. David Voegtlin, entomologist with the Illinois Natural History Survey, recently completed a tour of buckthorn sites in Illinois, Indiana, Michigan, and Ohio. He was looking for soybean aphid colonies on buckthorn plants. In his words, "We managed to find some colonies at every major Rhamnus cathartica [common buckthorn] location that we visited from N.E. Indiana to S.E. Michigan/Toledo to Moline, IL." The colonies were small and uncommon, for the most part, but alatoid nymphs (nymphs that will mature into winged adults) were found at all locations, indicating that the aphids were preparing to fly to soybean fields. Finding suitable soybean fields in some areas of the Midwest will prove to be a challenge for soybean aphids. There will be more on this topic in a near-future article in the Bulletin.

Entomologists at Michigan State University and the Ontario Ministry of Agriculture, Food and Rural Affairs have already found soybean aphids on very small soybean seedlings, similar to their findings in 2007. It remains to be seen what will develop elsewhere, with initially low numbers of soybean aphids and not many suitable soybean fields at the time of the aphids' migratory flights.

In "The Hines Report" for June 10, Ron also notes captures of adult corn earworms and southwestern corn borers, both of which can cause problems in cornfields, especially in southern Illinois. So there are plenty of insect pests to consider at the moment, but hardly any that are significant, imminent threats to corn or soybean production.--Kevin Steffey

Author:
Kevin Steffey

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