Damage and economic threshold of the third generation of cotton bollworm in the Yangtze River basin cotton region of Jiangsu Province

Abstract

Abstract: The impact of the third generation of cotton bollworm Helicoverpa armigera on shedding of buds, bolls, on bolling was studied by inoculating its larvae to cotton plants. The results showed that the shed rate of buds, bolls damaged by the larvae had the greatest impact on bolling,, its direct path coefficient was up to -0.8917.The larval population density, the number of buds, bolls damaged by the larvae impacted bolling mainly through the damaged shed rate during inoculating stage,, their indirect path coefficients were -0.8894, -0.891 respectively. Both of the direct, indirect path coefficients of natural shed rate during inoculating stage to bolling were small, which showed that the cotton had little capacity of compensation while the third generation cotton bollworm occurring. The investigations of damage number by larvae showed that the damage equivalent of the 1st～6th instar larval were 0.02, 0.14, 0.31,0.47, 0.84, 1.54 old bolls respectively.Based on direct, indirect benefits from controlling,the economic threshold of the third generation of the bollworm was worked out to be 26 accumulated eggs per 100 plants.

CLC Number:

S431

YANG Yantao, WANG Donghua, ZHU Minghua . Damage and economic threshold of the third generation of cotton bollworm in the Yangtze River basin cotton region of Jiangsu Province[J]. Chinese Journal of Applied Ecology, 2001, (1): 86-90.

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