I’ve had several questions about the use of Dimilin on soybeans.  Dimilin 2L is an insecticide that is typically applied at a rate of 2 oz/acre.  It provides a fairly substantial residual control of a FEW pests.  For our geography, it provides excellent control of green cloverworm, immature stages of grasshoppers and decent control of cabbage loopers (not soybean loopers).  That’s about it, and none of these insects commonly cause economic injury (although they are commonly seen).  Dimilin is more widely used in the Gulf Coast States because they also routinely encounter velvetbean caterpillar, which is also well controlled by Dimilin (but an extremely rare problem in Tennessee).

Dimilin provides no meaningful control of stink bugs and suppression (at best) of soybean loopers, so early sprays will not help with these pests.   Dimilin is promoted, including language on the label, as a yield enhancement product.  I do not have data from my trials to support any kind of physiological yield enhancement.  On a couple of occasions, a competitive treatment made as needed has been a better treatment because stink bugs were the primary pest (link to example).

I don’t like being a naysayer, but it’s my job to offer opinions on pest control.  I have a difficult time justifying making an automatic application of Dimilin when applying a fungicide.  If it happens to be one of those years where green cloverworms are unusually abundant, like 2012, then you’ll feel smart.  However, proper scouting should detect this pest before economic injury occurs, and they are inexpensive to control with mid-rate pyrethroids.  I’m not sure what the rush is to get the insecticide out well before an infestation of green cloverworms that may never occur.  On the upside, if you are needing to treat for cloverworms or cabbage loopers, Dimilin will not be very disruptive on beneficial insect populations.  This could help keep you out of problems with corn earworm or soybean loopers later in the season.

I’m repeating myself, but often the best thing to do is spend more time scouting and less time spraying.  However, I always encourage people to make a fair comparison on their own farms.  Try some test strips or splitting a few fields and see how the yield shakes out.