Insecticide seed treatments in soybeans

What is the importance of a neonicotinoid insecticide seed treatment in soybeans? Basically it is a risk management tool. Utilizing the early soybean production system, growers are planting soybeans much earlier than in the past.

Soybean seedlings have a tremendous amount of vigor compared to cotton seedlings and can tolerate a substantial amount of insect injury during the seedling stage. However, early planted soybeans can encounter less than optimal air and soil temperatures. These conditions stress plants and can reduce vigor, and under the right conditions soybean seedling growth can be similar to that of cotton seedlings. Insect injury under these conditions is an additional stress.

There is a fairly broad complex of insect pests that can attack soybean seedlings. These include bean leaf beetle, grape colaspis, threecornered alfalfa hopper, white grubs, thrips, and others.  Some of these pests can only be managed at planting. Also, uncommon and unexpected insect infestations can occur.

An example of this is illustrated in a trial conducted at the Delta Research and Extension Center during 2012. Beginning at emergence, the trial was severely infested with pea weevil.  Pea weevil is not a common insect pest of soybeans, but is an example of unexpected events that can happen. Infestations reduced yield in the plots without an insecticide seed treatment by 74 percent to 77 percent.

Results from more than 100 university trials in the Mid-South demonstrated a positive response to a neonicotinoids seed treatment in at least 70 percent of the trials. During 2010, assuming a yield response of 2 bu per acre, a crop value of $10.40 per bu, 70 percent of the soybean planted with an insecticide seed treatment, and 1.98 million acres of soybeans planted in Mississippi, it is estimated that the use of insecticide seed treatments in soybeans resulted in a value of $28.8 million to Mississippi soybean growers.

There are several factors growers should consider when deciding on the use of an insecticide seed treatment in their soybean production. These include soil conditions with respect to seed germination, amount of plant residue, burn down herbicide application timing, field history with respect to seedling insect pests, yield potential of the field, and risk management.