Development Of Herbicide Tolerant Strain Of Zygogramma Bicolorata For Effective Management Of Parthenium Hysterophorus L

Abstract

newline The present study entitled Development of herbicide tolerant strain of Zygogramma bicolorata for effective management of Parthenium hysterophorus L. revealed that application of 2, 4-D and glyphosate herbicides have caused negative impacts on larval development, longevity, reproduction as well on other biological parameters of Z. bicolorata. Significant effect was found in total larval developmental period when exposed to 2, 4-D (23.21 days) and glyphosate (19.70 days) treatments when compared to control (17.44 days). Both pre-pupation and pupation period enhanced significantly with application of 2, 4-D over control. Considerable negative effect was also observed in pre-oviposition, oviposition, fecundity, egg viability and post-oviposition which is more pronounced in 2, 4-D than glyphosate. Development of tolerance in beetle to glyphosate revealed that LC50 value increased from 1.694 to 11.717 with increased resistant ratio from 0.00 to 6.916. For 2, 4-D, LC50 value increased from 0.919 to 6.232 with increased resistant rate to 6.781 fold. Genetic analysis of tolerant strain for both herbicides and their crosses revealed that the LC50 values were significantly higher (plt0.05) than susceptible strains. The LC50 value of F1 progeny from tolerant cross viz., Tolerant Female X Susceptible Male and that of reciprocal cross were found intermediate with LC50 value of tolerant and susceptible parent strains in both tested herbicides. The degree of dominance in glyphosate and 2, 4-D crossed Tolerant Female X Susceptible Male appeared to be completely dominant but incomplete dominance in Tolerant Male X Susceptible Female in F1 generation. The net house trial of glyphosate and 2, 4-D herbicide tolerant and susceptible strains revealed that maximum mortality of larvae was observed in susceptible than tolerant after 0, 1, 2, 3, 4 and 5 days of treatment respectively. The percent defoliation was significantly higher in tolerant than susceptible grubs. Larval development period in tolerant and susceptible