We have heard reports of growers spotting a few soybean aphids in their fields. Finding aphids at this time of year is consistent in the past—we have seen them arrive later and later. We do have a lot of late-planted soybean that are in R4 or R5 stage soybean.
Remember that our economic threshold to treat soybean aphids is a rising population of 250 aphids per plant. But also remember that, at higher growth stages (>R6) the threshold increases dramatically. At this point it is important to note that none of the fields in Ohio have reached treatable levels. Given the aphids’ arrival, the growth stage of soybean and the oncoming onslaught of natural enemies, it may be unlikely that we see any significant impact from soybean aphids this year, but we should monitor our fields. An additional word of caution—many of you have heard that insecticide resistant soybean aphids have been found out West (especially Minnesota and Iowa). While we have not heard of any resistant aphids in Ohio, we certainly do not want to encourage their presence by applying insecticides when we don’t need to.