Al-Sarar, A. S. F.R. Hall and Roger. A. Downer (2006). The impact of spray application methodology on the development of resistance to Cypermethrin and spinosad by Fall Armyworm Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae). Pest management science 62(11) 141-149
Abstract: The development of resistance to an insecticide under various type of application methods has yet to be reported in the literature. Colonies Five fall armyworm reared in the chamber for 10 generations before starting topical application bioassay. From each FAW colony, 200-500 3rd -4th –instar larvae were fed for 72 hours on corn plant sprayed with cypermethrin or spinosad at minimum application rate (20 g ha-1) using the small droplet size nozzle XR8001vs (VMD 163µm) the large droplet nozzle XR8008vs (VMD = 519.1µm). surviving larvae were transferred to untreated corn leaves to complete their life cycle. Next generation 3rd instar larvae of each colony were topically dosed with technical cypermethrin or spinosad at 1µl/larvae and mortality recorded 24 hours post treatment. The results indicated that cypermethrin demonstrated an insecticidal activity greater than spinosad and the cypermethrin LD50 lines moved to the right faster than spinosad indicating an increased tolerance of cypermethrin. Generally, larvae from all generations (F1-F7) under the XR8008vs treatments were less susceptible to cypermethrin and developed resistance faster and to higher levels than larvae from the XR8001vs treatments. The confidence limits (95%) of LD50 for all spinosad treatments indicated there was no significant difference from the LD50 value of the susceptible reference strain. The results are a first indicating that application technology/ insecticide reaction may affect the rapidity of resistance development in certain pest/ plant scenarios but field studies are needed to confirm this conclusion.
Al-Rajhi D. H. A. S. EL Bakary, and A. S. Al-Sarar (1999). Toxicological and some biological effects of chronic exposure to sublethal doses of three insecticides on mail albino mice. 2nd Int. Conf. of pest control, Mansoura, Egypt, p35-44.
Abstract: In vivo toxicological and some biochemical effects of chronic exposure to the sublethal doses (0.05 and 0.1 of LD50) of diazinon, pirimiphos-methyl and cypermethrin on male albino mice were studied. A significant increase counts in white blood cells (WBCs) was noticed in mice treated with these insecticides. WBCs were increased sharply while red blood cells (RBCs) decreased when the animals were treated with formulated insecticides rather than technical forms. All the three insecticides reduced the hemoglobin concentration and the haematocrit value in general. Cypermethrin caused a significant increase in the mean cell volume (MCV), wheras, both of diazinon and primiphos-methyl caused high significant increase in MCV. Diazinon had little effect on brain acetylcholinesterase (AChE) activity, while plasma ChE was more sensitive to diazinon than RBCs acetylcholinesterase especially the formulated form. Formulated and technical pirimiphos-methyl had apparent inhibitory effect on brain AChE activity with the two doses tested. They also, produced a severe inhibition in plasma and RBCs AChE activities. Formulated technical cypermethrin produced a little inhibitory effect on brain AChE and a moderate inhibitory effect on plasma and RBCs AChE. All the tested insecticides caused a reduction in body weight gain, especially at the beginning of treatment. Diazinon was the most effective one in this aspect. Cypermethrin caused an increase in the body weight gain comparing with the control group. There was a general decrease in the organ weight index (W) of brain. Liver and spleen. However, a slight increase in the liver weight of the cypermethrin treated animals was noticed.