Efficacy of entomopathogenic nematodes against the larvae and adultsof the tomato leafminer Tuta absoluta in soil treatments andtheir compatibility with the insecticides used against this insect

Abstract: The efficacy of soil treatments of three species of entomopathogenic nematodes (EPN)(Steinernema carpocapsae, S. feltiae and Heterorhabditis bacteriophora) against Tuta absolutalarvae and adults was examined under laboratory conditions. The effect of some insecticides usedagainst T. absoluta in the survival, infectivity and reproduction of these native species of EPNswas also evaluated.Soil application of EPNs gave a high control of larvae when falling into the soil forpupation: 52.3%, 100%, and 96.7% efficacy was recorded for S. feltiae, S. carpocapsae andH. bacteriophora, respectively. The mortality of the adults emerging from soil was 0.5% forS. feltiae and 79.1% for S. carpocapsae. The insecticides tested have a negligible or moderateeffect on EPN survival, infectivity and reproduction. For all insecticide treatments and exposuretimes, H. bacteriophora was more sensitive than S. feltiae and S. carpocapsae. Nematodes thatsurvived were able to infect G. mellonella larvae with no significant difference from the control.The larvae affected by the insecticides served as suitable hosts for the infection and reproductionof the nematodes. These results suggest that the larvae of T. absoluta falling from leavesfollowing insecticide application could be a suitable host for nematodes, thereby increasing theirconcentration and persistence in the soil. This study demonstrates the suitability of soilapplication of EPN for controlling T. absoluta.