Soybean Fungicide/Insecticide Trial

Both strip trial and plot trial results from southern states have shown increases in soybean yields with the application of a fungicide/insecticide treatment even in the absence of significant disease or insect pressure in the fields. Possible explanations of the yield increases include the control of late season soybean diseases such as pod and stem blight that might be reducing yield more than previously realized, a delayed maturity or greening effect, etc. The most common fungicide/insecticide combination used in the early trials was Quadris (6.6 fl. oz per acre) + Warrior (2.56 fl oz per acre). Since Headline received registration for use on soybean, it has also been used in these types of trials. Trials from central and northern states have not shown as large or consistent yield increases as trials from southern states.

Soybean fungicide/insecticide trials were established at three Missouri locations during the 2004 season, repeated during the 2005 season and continued this season to evaluate the effect of the fungicides Quadris and Headline alone and in combination with the insecticide Warrior on yield of two soybean varieties. Fungicide and/or insecticide applications were made with a tractor mounted plot sprayer when plants were in the R3 stage of growth. Plots were evaluated periodically throughout the growing season for disease and insect problems and yields were taken.

2004 Results:
Although there were trends within the yield data, the only variety/location that had statistically significant differences in yield was Morsoy 3712 at the Bradford Research Center. There the Headline alone had the highest yield, followed by Headline + Warrior and the untreated check had the lowest yield.

2005 Results:
Although there were trends within the yield data, none of the variety/locations had statistically significant differences in yield. Insect pressure was low at all locations. Septoria brown spot was fairly widespread at all three locations but few of the other foliage diseases developed. The Hundley-Whaley site had adequate and timely precipitation over the season. Both Greenley and Bradford sites suffered from drought stress.