Insecticide seed treatments
Thiamethoxam (Syngenta), clothianidin (Bayer and Valent) and imidacloprid (Monsanto) are three insecticides that are widely used as soybean seed treatments, usually in combination with one or more of the above fungicides. They are labeled for numerous insects, including soil pests such as seedcorn maggot, white grub, and wireworm, and early season foliar insects such as soybean aphid and bean leaf beetle.
However, our experience is that the only soil pest of significance on soybean in Ohio is seedcorn maggot, and then only when a green, living cover or manure is incorporated into the soil prior to planting. This is the only scenario we have see seedcorn maggot issues. None of the other soil pests appear to occur in Ohio on the crop. Although these seed treatments will offer control of the foliar insects that are listed, they are seldom if ever needed.
Although bean leaf beetles will occur on early-planted soybeans, they are almost never reach economic levels, and even then, can always be controlled with a foliar insecticide spray following scouting. If growers are planting soybean for seed or food grade purposes and have had problems with bean pod mottle virus, they might consider a seed treatment to potentially offer suppression of the virus, albeit it will not be controlled.
With soybean aphids, growers should realize two things. First, Ohio aphid populations are on a two-year cycle, and few aphids are observed in even numbered years, which should be the case in 2014. Second, most aphids show up in our fields in later June, not in May. Thus, there are usually no aphids to “control” even in the odd numbered years early in the season. At most, a grower might delay aphid population growth in mid-summer by a week when using a seed treatment. But if conditions are right for aphids to achieve economic levels, a foliar treatment will still be necessary; you will still be paying for and making two insecticide treatments.
Thus, growers should consider whether or not insecticide seed treatments are really necessary prior to spending the additional money for an insecticide treatment that perhaps is not necessary nor that effective.