The Effect of Some Plant Extracts on Mortality, Fecundity and longevity of the Tomato Leaf miner Tuta absoluta

Abstract

This study was conducted at the laboratory of the entomology, Department of Plant Protection, College of Agricultural Studies, Sudan University of Science and Technology (SUST) Shambat to evaluate the effect of hexane and ethanol organic extracts of jatropha Jatrophacurcasseeds,leaves, neem Azadirachta indicaA. Juss, seeds, argel Solenostemma argel Del stems and malathion 57% EC on mortality, fecundity and longevity of the tomato leaf miner Tuta absoluta. Four concentrations of each extract were prepared and tested against two-day old adults. The results showed that all tested concentrations gave significantly higher mortality percentages than the control. The LC50 of the ethanolic extract of jatropha leaves after 24, 48 and 72 hrs of exposure were 15.649, 6.684 and 4.435 respectively whereas those of the hexane extract of jatropha leaves were 6.266, 1.881 and 1.583 respectively. The results clearly showed that the LC50 obtained by jatropha leaves hexane extracts after 24, 48 and 72hrs of exposure were consistently lower than their counterparts of jatropha leaves ethanolic extract. This may indicate that the active ingredient in jatropha leaves is easily extracted in hexane rather than in ethanol. The LC50 of the ethanolic extract of jatropha seeds after 24, 48 and 72 hrs of exposure were 6.406, 2.278 and 2.493 respectively whereas those of hexane extracts of jatropha seeds were 6.219, 5.629 and 3.139 respectively. On the other hand the hexane and ethanol extracts of neem seeds generated the same LC50 values after 24, 48 and 72 hrs of exposure and the LC50 values obtained were 7.143, 3.592 and 3.333 respectively. The mortality results generated by the 15% hexane and ethanol extract of both jatropha leaves and seeds as well as neem seeds were not significantly different from the standard, malathion, after 48 and 72 hrs of exposure which is an indicative of the potency of these extracts. The LC 50 values of the ethanol extract of argel stem after 24, 48 and 72 hrs of exposure were 17.716, 8.336 and 6.860 respectively whereas those of hexane extract were 26.191, 26.191 and 13.571 respectively. The fecundity study results showed that all tested concentrations of hexane and ethanol extracts of jatropha seeds, leaves, neem seeds and argel stems generated a significantly lower fecundity of the treated insects than that of the control. All tested concentrations greatly reduced the fecundity of the treated insects, but there was no significant difference in fecundity obtained by insects treated with different concentrations. The longevity studies showed that all insects treated with the different concentrations of organic extracts gave significantly lower longevity percentage than the control throughout the experimental period.