Population Density and Effect of Some Toxic Compounds on Aphis gosspyii Glover and their Predators, Parasitoids and Major Elements in Okra Plants

Field experiments were conducted during 2014 and 2015 seasons at El-Riad, Kafr El-Sheikh governorate, to study the population density of Aphis gosspyiiGlover, predators and parasitoids on different okra varieties; white velvet, Sakha1 and balady. Also, efficiencies of certain compounds; Imidacloprid, Primicarb, Acetamipirid, Primiphos-methyl and Azadirachtin in reducing the population density of A. gosspyii and their side effects on predators and parasitoids were evaluated. In addition, chlorophyll content and major elements; potassium (K), nitrogen (N) and phosphorous (P) in okra leaves were assessed. The population densities of A. gosspyii and chlorophyll content were higher on balady cultivar than on other cultivars. Significant differences were found among three cultivars on population density of A. gosspyii.  Population densities of predators were lower on Balady than on other cultivars in the two seasons, except syrphids in 2015 season. Syrphids induced high significant reduction in aphid population in 2014 and Aphidoletes aphidimyza (Rondami) in 2015. The population density of A. gosspyii, parasitism (mummification), parasitoid Lysiphlebus fabarum (Marshall) and hyperparasitoid, Pachyneuron aphidis(Bouché) were recorded in May, June and July on white velvet and Sakha 1, while no parasitism was detected on Balady cv. All the tested compounds showed a high effect, in reducing the population A. gossypii. Also, Pirimi adwia and Etox induced a high effect on predators followed by Volley and Egydoor that were of moderate effect, while the other compounds induced the lowest. In addition, Pirimi adwia and Cezar were the highest harmful compound in reducing the parasitoid, L. fabarum population followed by Etox and Egydoor, while Volley and Safe oil was the least effects. Chlorophyll content and elements (K, N and P %) significant differences were found with the treatments. Chlorophyll content increased significantly by Pirimi adwia, Cezar and Volley treatments, while it was the least with Confidate treatment on leaves okra. Also, K% had the highest with safe oil followed by Etox and Pirimi adwia treatments, while it was the least with Cezar and Volley. In addition, N% had the lowest with safe oil and Confidate treatment, while it was the highest with Pirimi adwia treatment. P% had the highest with safe oil.