Studies on the Spatial Distribution Pattern of Soybean Aphid and Sampling Techniques

摘要

The results of our studies on the spatial distribution patterns of aphid populations and of the aphid infested plants in the field showed a spatial distribution pattern of aphids aggregated at certain density levels. Characteristics of aphid behavior, such as mutual attraction between individual aphids, were the cause for aggregation of soybean aphids. The basic elements of distribution are individual aphid colonies. The aphid infested soybean plants were either uniformly or randomly distributed when infestation rates were low, and uniform distribution prevailed as the infested rates increased to higher levels. Sampling methods such as parallel, chessboard and “Z” pattern sampling, were all applicable in the investigation of aphid population density. In addition, by referring to the linear regression equation between average crowdedness and mean proposed by Iwao and applying the ? and ? values from the equation to the formulae of theoretical sampling numbers and sequential sampling, we may obtain the theoretical sampling numbers and results of sequential sampling for the investigation of both aphid density and the aphid infestationrate of soybean plants.