Comparative Efficacies of Day and Night Applications of Bacillus thuringiensis to Control Cotton Leafworm Spodoptera littoralis Boisd. under Hot Weather Conditions

摘要

In the recent years there have been rapid developments in the use of Bacillus thuringiensis for insect control, notably regarding the timing and equipments that are effective against the target insect pests and improvement of application technology, However in a hot country like Egypt the rapid inactivation of application technology, However in a hot country like Egypt the rapid inactivation of entomopathogens, such as B. thuringiensis, by ultra violet (UV) radiation and heat of sunlight limits their residual activity and effectiveness in the field. Under such conditions the half life of Bt formulation may be reduced to less than 24 hours. It can be especially limiting in such sunny conutries where daytime lasts more than 12 hours daily. Hence the target insects, then, spend much of the daytime hiding in sites that are sheltered and thus, protected from the applied bioinsecticides that are loosing their efficacy rapidly due to exposure to such hot weather conditions. On the other hand under such conditions applications usint high concentrations of the bioinsecticide is necessary to achieve appropriate pest control.