LABORATORY STUDIES ON THE RELATION BETWEEN THE EFFECT OF "NEONICOTINOID" INSECTICIDES AND THE HYPOTHESIS "HORMOLIGOSIS" ON THE BIOLOGY OF TWO SPOTTED SPIDER MITES

Abstract

Two methods were used to treat female of two spotted spider mite with neonicotinoid insecticides.First of them are direct spraying on females by using three concentration of each insecticide( recommended concentration,half and quarter of recommended concentration) Imidacloprid had caused an increase the number of eggs laid by the female to means of 8.30, 7.54, 9.37 eggs/day with the respective dosges used. Thiamethoxam treatments showed a means of 7.64, 7.12, 7.75 with respective to the used concentration. However, the means for the control treatment was 3.81, 4.70, 5.45 eggs/ day. Statistical analysis showed significant differences between the treatments. Similarly Imidacloprid treatment had an obvious effect on the longevity 11.3 days followed by Thiamethoxam with longevity 9.70 days, while the longevity in the control was 8.00 days. The differences between the treatments were highly significant. The second method that was used to treat the mite female was by dipping discs of cotton leaf in solutions containing different concentration of the used insecticides. The results showed that Imidacloprid treatments had the highest effect on the fecundity with means of 8.90, 7.05, 9.15 with respective to the different concentrations followed by Thiamethoxam treatments with means of 6.84, 6.57, 7.14 while the control treatment showed a mean of 4.60, 4.58, 5.31. statistical analysis showed significant differences between the treatments. In regard to the effect of dipping method on female longevity, the results showed that Imidacloprid treatment had elongate the female life span to 11.00 days compared to that found with Thiamethoxam treatment 9.33 and 7.66 recorded for Thiamethoxam and control treatment.In conclusion, the increased effects that accured when nicotinoid insecticides were used can be explained by the hypothesis of "Hormoligosis".