Effect of Some Commonly Used Weedicides on the Parthenium Beetle Zygogramma bicolorata Pallister (Coleoptera : Chrysomelidae)

Abstract

The neotropical plant Parthenium hysterophorus L. (Asteraceae) is a serious weed of agricultural fields, pastures and waste lands in most parts of India (Krishnamurthy et al., 1977). The mexican beetle Zygogramma bicolorata Pallister (Coleoptera : Chrysomelidae), releases of which were iniitiated in 1984 (Jayanth, 1987), is proving to be a promising biological control agent in and around Bangalore (Jayanth and Geetha Bali, 1990). A number of weedicides have been recommended for the control of, P.hysterophorus in India (Krishnamurthy et al. , 1977 ; Muniappa et 01., 1980; Challa, 1987). In situations where chemical methods are preferred, it would be ideal to use weedicides that are least harmful to Z.bicolorata . With this in view, the impact of some commonly used weedicides were tested for their safety to the beetle.