Evaluation of Resistance Development in Bemisia tabaci Genn. (Homoptera: Aleyrodidae) in Cotton against Different Insecticides

SIMPLE SUMMARY: In the tropical and sub-tropical regions of Asia, Africa, and America, the Bemisia tabaci (cotton whitefly) has attained a major pest status of cotton. It produces injury to the plant by feeding, excreting honeydews, and by transmitting viruses on many crops. The heavy application of insecticides for controlling the insect pest is one of the main reasons for the outbreaks of whitefly. Due to several reports of control failure of the whitefly, the present study was conducted to evaluate the resistance development in B. tabaci. Therefore, the field population of B. tabaci was collected, and the resistance development was evaluated against the commonly used insecticides. For evaluating the development of resistance, the B. tabaci was selected with the insecticides under the controlled laboratory conditions. The data of mortality was calculated at each generation, and the overall development of resistance up to five generations was evaluated. Results showed that the field collected population was susceptible to the selected insecticides at G1, indicating their effectiveness. However, a continuous selection for only five generations resulted in a significant increase in the resistance development. The present study provided very valuable information on the resistance development in B. tabaci. ABSTRACT: Cotton is a major crop of Pakistan, and Bemisia tabaci (Homoptera: Aleyrodidae) is a major pest of cotton. Due to the unwise and indiscriminate use of insecticides, resistance develops more readily in the whitefly. The present study was conducted to evaluate the resistance development in the whitefly against the different insecticides that are still in use. For this purpose, the whitefly population was selected with five concentrations of each insecticide, for five generations. At G1, compared with the laboratory susceptible population, a very low level of resistance was observed against bifenthrin, cypermethrin, acetamiprid, imidacloprid, thiamethoxam, nitenpyram, chlorfenapyr, and buprofezin with a resistance ratio of 3-fold, 2-fold, 1-fold, 4-fold, 3-fold, 3-fold, 3-fold, and 3-fold, respectively. However, the selection for five generations increased the resistance to a very high level against buprofezin (127-fold), and to a high level against imidacloprid (86-fold) compared with the laboratory susceptible population. While, a moderate level of resistance was observed against cypermethrin (34-fold), thiamethoxam (34-fold), nitenpyram (30-fold), chlorfenapyr (29-fold), and acetamiprid (21-fold). On the other hand, the resistance was low against bifenthrin (18-fold) after selection for five generations. A very low level of resistance against the field population of B. tabaci, at G1, showed that these insecticides are still effective, and thus can be used under the field conditions for the management of B. tabaci. However, the proper rotation of insecticides among different groups can help to reduce the development of resistance against insecticides.