Just what you need- another problem to worry about during the already problem-laden 2009 season, right? Ignoring it could eventually cause yield loss and lower income, especially in northern Indiana. That's possible if conditions favor soybean aphid development, particularly later in the season.
Discovery of the first soybean aphids of '09 last week inside the state borders is a reminder that soybean aphids are a pest you can't afford to forget about. Earlier this decade this pest caused losses of 10 bushels per acre or more across parts of northern Indiana, particularly northeast Indiana, and in more than one season.
Christian Krupke and John Obermeyer, Purdue University entomologists, note that the first sighting came from a familiar hot spot for aphids, especially early in the season. They were positively identified by a credible source near the St. Joseph and Marshall County line, feeding on young soybeans. The report indicated up to 40 aphids per plant while the beans were in the early vegetative stage.
Treatable populations are typically more like 250 aphids per plant. However, the entomologists suggest that if aphids are present, the wise thing to do is to monitor and scout those fields.
"Indiana is a 'second-tier' aphid state," Krupke says. "In some areas we typically don't get the large early infestations that states such as Michigan and Minnesota do, probably because we have less of the over-wintering host plant, which is buckthorn."
Since northern Indiana is closes to these 'hot bed' states, they're likely to see aphids first,. That's why the citing in north-central Indiana one county down from the state line is not surprising to the entomologists.
August is typically the heaviest month for aphids in Indiana, Krupke notes. Purdue will begin tracking aphid numbers in their sentinel plots which also serve as outpost alert centers should Asian rust enter the state. You can find frequent updates once tracking and scouting begins in these plots at: www.srbusa.net.
It's still too early to tell what aphid numbers might be like in Indiana, especially northern Indiana, by the time August rolls around. The sentinel plot tracking information should help provide a guide as the season develops. Monitor that data and other numbers closely, and keep an eye on your own fields, both now and as the season moves into the critical August phase for soybeans.