Abstract
The results of studying the effect of cold storage period of Chlorpyrifos 48% EC. Alphacypermethrin 5%EC and mixture of Chlorpyrifos and Cypermethrin on their longevily and efficiency in controlling Stephanitis pyri (Fab.) revealed that the insecticides efficiency decreased with increasing cold storage period. Alphacypermethrin efficiency in controlling S. pyri reached 28.92% when stored for tow months at 5 o C in comparison with 45.58% for control ( stored at room temp. ). follwed by the mixture of Chlprpyrifos and Cypermethrin 30.25% when stored for tow months at 5 o C compared with 48,58% for control , and then followed Chlorpyrifos 30.29% when stored for three months at -5 o C in comparison with 45.67% . All tested Insecticides lost their activity after 21 days from treatment at the three cold storage periods .