Effects of Defoliation on Midsouth Soybean Yield

Every year in Mississippi injury from defoliating insects are responsible for causing major yield loss to soybean producers.  Insects responsible for this damage include bean leaf beetles, soybean loopers, velvetbean caterpillars, green cloverworms, armyworms, grape colaspis, flea beetles, and grasshoppers.  In 2013, defoliating insects alone cost Mississippi producers losses totaling $42,358,460.  Previous research has shown that excessive foliage loss that occurs during the R3-R5 growth stages can have devastating effects on yield.  In order to refine the current treatment recommendations and help apply them to situations commonly encountered by producers, tests were conducted during the 2015 growing season in the hills and delta region of Mississippi.  Soybeans were defoliated at various levels and growth stages throughout the growing season to evaluate the effects of multiple defoliation events. Plant heights and leaf area index was recorded periodically throughout the growing season.  Leaf area index values correlated strongly with soybean yields. In vegetative stage soybeans yield losses were not significant until near plants reached near 100% defoliation.