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Bollworm: Response to Methyl Parathion and Permethrin in South Texas and Mexico

D. A. Wolfenbarger


 
ABSTRACT

From 1969 to 1980s resistance to methyl parathion of the bollworm, Helicoverpa zea (Boddie), indicated by an LD50 value of >7.5 g/larva, was found in populations from San Salvador, El Salvador and Tapachula, Chiapas and Tampico, Tamaulipas, Mexico. In 1992 a population from southern Tamaulipas was resistant to methyl parathion . This LD50 of >7.5 g /larva was proposed as a resistance threshold for methyl parathion to populations of bollworm. Results were organized to show response of bollworm to 34 populations from methyl parathion in tropical areas of Mexico to subtropical areas of Mexico and south Texas. In 1990-1991, 1993 and 1995 resistance to methyl parathion was not found in populations of the bollworm collected from corn or cotton in south Texas or in northern Tamaulipas, Mexico. No resistance to permethrin was shown by 29 populations of bollworm collected from El Salvador, Mexico or from the United States in 1981-1983 and 1990-1991. None of the LD50 values for permethrin exceeded a proposed resistance threshold of >0.2 g/larva. Many of the same collections were treated with both insecticides.



Reprinted from Proceedings of the 2000 Beltwide Cotton Conferences pp. 1375 - 1380
©National Cotton Council, Memphis TN

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Document last modified Saturday, Jun 17 2000