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
作者:
R. A. Higgins,
L. P. Pedigo,
D. W. Staniforth,
期刊:
Environmental Entomology
(OUP Available online 1984)
卷期:
Volume 13,
issue 4
页码: 917-925
ISSN:0046-225X
年代: 1984
DOI:10.1093/ee/13.4.917
出版商: Oxford University Press
数据来源: OUP
摘要:
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.
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