Still working on your business plan for the 2007 crop year? Sharpen your pencil one more time if you haven't included the cost of insecticides for your soybean crop. Aphid populations in the upper Midwest are expected to be near record highs, according to university entomologists.



"Most soybean producers remember 2003 as a bad year for soybean aphids, but 2007 could be even worse," says Bob O'Neal, entomologist for Purdue University. "The numbers of aphids captured last fall were more than we have recorded in previous years," he continues. "Soybean producers will need to be very vigilant this year to minimize yield loss to the tiny little insect."



Checkoff-funded research has helped develop a system that can predict the relative magnitude of summer aphid populations by monitoring the number of aphids moving into overwintering sites. Scientists use 20-foot tubes that stick up in the air with fans on the lower end that suck air and insects into the tube. The numbers of aphids drawn into the tube are recorded weekly. The more aphids recorded, the greater the producers' risk.



Although the numbers of insects moving to overwintering sites in 2006 were high, the trend is not unexpected. Generally, aphid populations tend to be cyclical, building to threshold levels every two years. Soybean aphids were very severe in 2003 then dropped off in 2004. They came back again in 2005 and were very severe in states like Michigan and Minnesota. In odd years, aphids abound.



The reason? Natural predators.



"The Asian ladybird beetle is one of our best means of natural control of the soybean aphid," says O'Neal. The soybean aphid is food for the ladybird beetle. As aphid populations increase, so does the population of the ladybird beetle. Eventually the ladybird beetles consume enough aphids that the aphid population declines, reducing the number of overwintering aphids and reducing the soybean producers risk the next cropping season.



Soybean producers can generally expect the aphid population to approach threshold levels in late June or early July. Producers should begin scouting when the soybean plant begins to flower. Monitor soybean fields individually because aphid numbers can vary widely. Treatment options also vary widely so check with your local crop advisor for treatment recommendations.



The first non-GMO, aphid-resistant soybean lines will be released in about four or five years. The University of Illinois discovered the source of resistance that has been incorporated into these lines. Checkoff-funded research continues at several Land Grant universities to find additional sources of resistance. The University of Minnesota reports having found several lines that appear promising.



Readers can monitor aphid progress throughout the year by logging on to various Web sites including www.planthealth.info and www.soybeanaphid.info. These sites will display the most up-to-date information available on aphid numbers in the upper Midwest. The www.planthealth.info site also offers free publications on management of soybean aphids, SCN and other pests.



SOURCE: North Central Soybean Research Program eNewsletter for January 2007.