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.

Reference Report for IND85019615

Title:	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.
Authors:	Higgins, R.A., Pedigo, L.P., Staniforth, D.W.
Source:	Environ. Entomol. 1984, 13 (4):917-925
Abstract:	We 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. Competition durations of velvetleaf were manipulated manually (roguing) and chemically (postemergence herbicide). A temperature-dependent developmental model was used to determine realistically the rate and intensity of simulated GCW defoliation (imposed by hole-punching). 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. Increasing the intensity of defoliation resulted in a proportional linear reduction in grain yield. 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. At the plot level, little definable evidence of velvetleaf and GCW interaction was detected. On a stratum basis, consistency in velvetleaf-induced yield reductions was observed in the upper two-thirds of the canopy, whereas 2-year consistency in simulated GCW-induced losses was restricted to the lower two-thirds of the canopy. Nonadditive treatment interactions were consistently evident only in the central canopy stratum of soybeans near weeds. This study indicates that knowledge of velvetleaf prevalence in a field probably is not a prerequisite for using conventional monospecific economic injury levels in managing the GCW on fullbloom soybeans. assuming that a runaway velvetleaf infestation is not present

Funded by the USDA-ARS. Developed by the USDA-ARS SoyBase and Legume Clade Database group at the Iowa State University, Ames, IA

U.S. Public Domain