Environmental concerns about chemical insecticides serve as a strong impetus for the development of biological control agents or biopesticides. Biopesticides can be safer, more biodegradable, and less expensive to develop. Among biopesticides, insect parasitic nematodes in the families Steinernematidae and Heterorhabditidae possess tremendous potential as alternative to chemicals. They have a unique association with symbiotic bacteria, Xenorhabdus and Photorhabdus (Enterobacteriaceae), respectively (Akhurst, 1995, Boemare et al; 1993, Hussein and Abd el Aty, 2012) which is essential for the usefulness of these nematodes in the control of insects (Nouh and Hussein, 2014; Hussein et al, 2015).
However, the field efficacy of these nematodes is limited because of their vulnerability to environmental conditions such as low humidity and solar radiation (Gaugler et al., 1992). Also, many biotic and abiotic soil components affect nematode activity, infectivity, host finding ability and the rate of reproduction. Copper, an essentially required element by all organisms, could be toxic at its elevated concentrations in soils and may result in a range of effects including reduced biological activity and the subsequent loss of fertility (Dumestre et al. 1999). Pesticide application is of particular interest among different sources of copper pollution such as mining, industrial discharge and fertilizers (Nor, 1987). Besides its use as fungicides and algicides, it is also used in animal nutrition and fertilizers. Again, copper is used to kill the slugs and snails in irrigation and municipal water treatment systems (Kamrin, 1997). Hence, significant uncertainty remains in the prediction of impacts of pesticide application on the agricultural ecosystem (Liess, 2004).
Contrarily, Schiff bases and their complexes have been studied extensively as they possess many interesting features including biological and pharmacological activities (Sinha et al 2008, Panneerselvam et al 2005 and Karthikeyan et al 2006), e.g., their complexing ability towards some toxic metals (Sawodny and Riederer, 1977). Also, the complexes of the Schiff base have a variety of applications in biological, clinical and pharmacological areas (Hitoshi et al, 1997).
The aim of the present study is, therefore, to evaluate the biological effect of Cu ion, two Schiff base ligands and two complexes of copper on H. bacteriophora and S. carpocapsae juveniles. This will include the determination of influence of these agents on the infectivity and the rate of reproduction of the nematodes.