The soybean aphid has been a pleasant disappointment this year. While many of us were anticipating a repeat performance of widespread, economically damaging populations in 2004, the soybean aphid, for whatever reason, has fizzled. The aphid can be found throughout much of Iowa, but nearly all field reports are that populations are way below the economic threshold of 250 aphids per plant. The one reported exception is in Marion County. Steve Crozier, Smith Fertilizer and Grain, reported he was finding more than 50 percent of the plants with more than 250 aphids, and 500 aphids per plant was not uncommon.
I expect the last week of July to be a critical week for the soybean aphid situation. I dislike making predictions because there are so many factors that can influence insect growth and reproduction. However, I think that if populations have not reached the economic threshold by August 1, then there is a high probability that they won’t. We’ll know at the end of August if I was right.
This article originally appeared on page 103 of the IC-492(18) -- August 2, 2004 issue.