Synergism of mineral oil in the insecticide toxicity for Scrobipalpuloides absoluta (Lepidoptera: Gelechiidae)

Abstract

Using the immersion method for tomato leaves in insecticide solution, a series of bioessays was carried out in order to evaluate the possible synergistic effects of mineral oils in the insecticides abamectin, cartap, phentoate and permethrin to 3^rd and 4^th instar larvae of tomato leafminer. Different concentrations of the insecticides in water with and without 0.5% of mineral oil were prepared. Tomato leaves were immerged in insecticide solutions for 5s, dried in air, put in Petri dishes and infected with 40 larvae of Scrobipalpuloides absoluta (Meyrick, 1917), kept at 25^oC and 70% RU. Mortality was evaluated 24 hours later and through the ratios between insecticide CL₅₀ and insecticide + mineral oil CL₅₀, potency enhancement of insecticides were verified for all compounds ranging from 2.40 to 6.46 times. Through the ratio between CLs₉₉ the greater synergistic effects were observed in the mixtures abamectin plus mineral oil (15.96 times) and permethrin plus mineral oil (7.11 times) and lower synergistic effects were observed in the mixtures cartap plus mineral oil (2.14 times) and phentoate plus mineral oil (1.79 times).