| Popis: |
AbstractHelicoverpa armigera is a major threat for all cotton production areas in Ethiopia. Pests control with insecticides from a single chemistry group is common practice in most cotton farms, which may help to the development of insecticide resistance. The studies aimed to determine the susceptibility of the field population of H. armigera to pyrethroid insecticides. The experiment was carried out at Werer Agricultural Research Center under the laboratory condition using larva immersion and square dip methods. The selected insecticides were tested in seven dilutions levels. In each dilution 30 larvae of 3rd instars, H. armigera were treated in three replications along with pure water. A low level of resistance was detected for all tested locations to alphacypermethrin and a high resistance ratio to lambda-cyhalothrin and deltamethrin for Gewane and Werer populations. Aplhacypermethrin was the most toxic insecticide and its LC50 was low compared to other tested synthetic pyrethroids. Whereas, deltamethrin was the least toxic insecticide with high LC50. The LC50 value of the Goffa-Sawla population was significantly different among the populations for Werer, Upper-Awash, and Gewane in both bioassay methods. The study concluded that Helicoverpa armigera might have resistant to deltamethrin in Werer and Gewane populations. Further studies on the monitoring of resistance are recommended. |
