Effect of velvetleaf competition and defoliation simulating a green cloverworm (Lepidoptera:Noctuidae) outbreak in Iowa on indeterminate soybean yield, yield components, and economic decision levels

The authors evaluated the separate and combined effects of velvetleaf, Abutilon theophrasti (Medic), competition and simulated green cloverworm (GCW), Plathypena scabra (F.), defoliation on soybean grain yield and components of yield in a 2-year study. Velvetleaf stress was largely limited to soybeans near full-season weeds. As few as 4,386 velvetleaf plants per ha were capable of causing economic losses in soybeans. Under the conditions studied, 25 to 29 simulated GCW larvae equivalents per m of soybean row were required to cause economic loss in full-bloom soybeans. This study indicates that knowledge of velvetleaf prevalence in a field probably is not a prerequisite for using conventional monospecific economic injury levels in manageing the GCW on full-bloom soybeans.