The effect of microbial and chemical pesticides on different instars larvae of Colorado potato beetle in laboratory conditions

In this study, the susceptibility of different larval instars of Colorado potato beetle, Leptinotarsa decemlineata to Biobit containing Bacillus thuringiensis var. tenebrionis Ber., as microbial and imidacloprid as novel chemicals and phosalone as conventional insecticides was investigated in laboratory conditions. Colorado potato beetles were propagated on potato leaves planted in pots and their 1st, 2nd, 3rd, and 4th larval instars’ susceptibility was determined by bioassay test. LC50 values of Biobit for L1, L2, L3 and L4 were defined as 252, 613, 1731 and 3006 ppm after 144 hours, respectively. Also, LC50 values for imidacloprid and phosalone after 72 hours were 17.58, 41.35, 56.76 and 81.27 ppm and 447, 698, 1020 and 1297 ppm, respectively. Older insect larvae were more resistant to microbial and chemical treatments. Also, Colorado potato beetle was more susceptible to imidacloprid then phosalone and Biobit.