Efficacy of bio-insecticides on Tuta absoluta (Meyrick) (Lep.: Gelechiidae) in laboratory and field conditions

Abstract

Tuta absoluta (Meyrick) is a devastating pest of tomato. This pest is becoming resistant to many of the pesticides that used in the tomato fields. In this research, the efficacy of four bio-insecticides namely, thiocyclam, spinosad, Bacillus thuringiensis and azadirachtin (Azadirachta indica) were studied on the tomato leaf miner in the laboratory and field conditions. Laboratory experiments were performed in a randomized complete plot design with three replications against 1^st, 2^nd and 3^rd larvae. Field experiment was carried out on three larval stages based on recommended doses of pesticides in the form of a completely randomized block. The results showed that in laboratory conditions, LC₅₀ values and lower and upper bond with 95% confidence limits of thiocyclam, spinosad, B. t­ and azadirachtin on third instar larvae after 72 h, were 902.01(680.3- 1442.54), 1793.41 (1326.08- 2924.97), 2239.81 (2137.98- 2513.94) and 2572.09 (2423.62- 2736.74), respectively. In field experiments, thiocyclam and spiosad had the highest efficiency on mortality of the larvae with an average loss of 95.35 and 80.59%. B. t and azadirachtin with an average mortality of 67.29 and 66.40% had the lowest effect, respectively. The results showed that the third instar larvae were less sensitive than the first and second instar larvae for all pesticides. The results of two experiments show that spinosad, B. t and azadirachtin had less insecticidal efficacy compared with thiocyclam on tomato leaf miner. Recent study recommended using thiocyclam in integrated management of this pest.