Ovicidal and sublethal effects of pesticides used in greenhouse grown tomatoes on tomato leafminer Tuta absoluta (Meyrick) eggs

This study was undertaken to gather data on the effective and conscious use of pesticides applied in the control of an important pest, the tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) and other major greenhouse pests in tomato grown districts of Antalya which is a major tomato producing province in Turkey. The ovicidal and sublethal effects of pesticides, that are registered for control of T. absoluta namely spinosad, metaflumizone, indoxacarb, azadiractin and chlorantraniliprole+abamectin and those provisionally registered for use against other major greenhouse pests namely, acetamiprid, imidacloprid, pyriproxyfen, pyridaben, malathion, abamectin, emamectin benzoate and etoxazole as well, were investigated on T.absoluta eggs. Among the pestcides that were investigated spinosad, indoxacarb, azadirachtin, chlorantraniliprole+abamectin, abamectin, emamectin benzoate and metaflumizone were found to cause 40% and over ovicidal effect on T.absoluta eggs at recommended doses. Egg mortality led by 5 of them namely, spinosad, indoxacarb, chlorantraniliprole+abamectin, abamectin and emamectin benzoate was 100%. Sublethal doses of 7 pesticides that were mentioned above to have ovicidal effects plus the IGR pyriproxyfen were applied on T.absoluta eggs to assess their sublethal effects on the eggs and the larvae hatched, pupae and adults. The investigated biological parameters related to development, survival and reproduction were developmental duration and survival of the eggs, larvae and pupae and developmental time and overall survival; fecundity, preoviposition, oviposition and postoviposition periods, longevity sex ratio and survival of F1 eggs. The following changes were found in individuals that survived the sublethal doses of the pesticides: Duration of development of larvae and pupae, and developmental time of immature stages were shortened; survival of eggs and larvae, and overall survival were reduced; fecundity and survival of F1 eggs were reduced; oviposition period, and longevity of females and males were shortened. It would be necessary to conduct greenhouse experiments with the effective pesticides in order to confirm and to make use of laboratory data. If the results of investigations under greenhouse conditions were proven to be satisfactory in terms of ovicidal effects then chemical control strategy of T. absoluta may be modified to target eggs instead of the current target larvae. The pesticides investigated inflicted ovicidal effects at much lower doses than those recommended. Such a change in the control strategy may lead to a reduction in number of sprays and amount of pestisices used. The usefulness of the effective pesticides may be expected to increase because of their survival and reproduction reducing effects in individuals that survived the pesticide exposures. If such sublethal effects were proven to be dose dependent then by changing doses of pesticides it could be possible again to reduce the number of sprays and the amount of the pesticides used.