It comes in spurts, but every so often I get questions about how to eliminate fire ant mounds from soybean fields.  The primary issue is stoppages that occur when the combine header hits a good sized mound.  Operators may also endure a few stings while cleaning out the header. Soybean is more impacted because the plants are cut near the soil surface.  Most complaints in Tennessee are from the counties along the southern border (where fire ants are more common).

Unfortunately, there is no easy fix! Ant mounds are far more likely to cause problems in reduced-tillage fields, but tillage is not an attractive option for most fields in Tennessee. Repeated foliar insecticide applications are less effective than you might think, are costly, and may have negative side effects (including environmental impacts). However, repeated insecticide applications is one reason we see fewer and smaller ant mounds in cotton fields.

Fire ant baits have been used to reduce the number and size of ant mounds in soybean fields. There are many brands and types of fire ant baits, but its hard to find one labeled for use in soybean. One product, Extinguish Professional Fire Ant Bait, is labeled for use in crop areas. Esteem Ant Bait is a product from Valent that can also be used in soybean. A second problem is application.  These baits are applied as dry granules at a rate of 1-2 lbs/acre.  Thus, it requires some planning on how to spread this low amount across large production fields. It may be possible to blend the baits with dry fertilizers mixes, but the impact of this on efficacy is mostly untested.  A final issue is cost.  If memory serves, the lowest effective rates for these treatments will cost about $15/acre.  My experience has been that most producers are not willing to invest that much … they simply opt to live with the problem.  The good news is that fire ant populations may start out pretty low this coming year given the relatively hard winter.