Assessment of Development of Resistance in Cotton Whitefly Gennadius of Guntur Strain

A study was undertaken to assess the degree of resistance acquired by Bemisia tabaci Gennadius of Guntur strain through comparing with the base line data at LC ₅₀ level and with respect to recommended concentration at LC ₉₀ level. It was found that B. tabaci has developed 3.37, 3.12, 1.59 and 1.41 fold resistance to cypermethrin, monocrotophos, acephate and triazophos respectively at LC after 1993. All the six insecticides are less effective against the cotton whitefly of Guntur strain since the LC values of these insecticides are higher than the corresponding recommended concentrations which imply the acquisition of resistance.