Compatability of three virulant Egyptian entomopathogenic nematod strains and two organophosphus insecticids in controlling Zeuzera pyrina L. in olive orcherds

Abstract

This investigation aimed to explore the efficacy of three Egyptian isolates and/or strains of entomopathogenic nematodes and/or two recommended insecticides, to control Zeuzera pyrina L. under laboratory and field conditions. Results revealed that in all tested EPNs, LC50s were lower in larval stages than pupae. All nematode strains were not significantly affected by any of the tested concentrations of diazinox or basudin, i.e., IJs survival was held over 75% and 66% when checked by 1500 and 4500ppm, respectively. Insecticides exposure period affected to some extent the nematode survival regardless of their concentration. Z. pyrina highest mortality (100%) was obtained from the mixture of basudin (half recommended rate) and LC90 of EGB20 strain. Data extracted from field results recommends that, all tested nematode strains at 1000 IJs/ml proved to be more effective against Z. pyrina in olive tree than diazinox and basudin. The EGB20 strain showed superior effect over EGB13 and EBN16, especially with injection methods and addition of evaporation retardant agent. The joint action of mixing nematode strains together with insecticides as a co-toxicity factor did not achieve its goal or fulfilled our expectations. Yet, combinations of EGB13 and EGB20 strains, proved to be slightly higher in their effectiveness than using insecticides or entomopathogenic nematodes separately and multiple co-applications of insecticides and nematodes were associated with a longer protection period of olive trees. The current study might be an important step towards establishing an efficient control strategy capable of minimizing Z. pyrina population below economic thresholds in olive farms.