IMPACT OF CHEMICAL AND BIOINSECTICIDES AND THEIR COMBINATIONS ON ENTOMOPHAGOUS INSECTS IN COTTON FIELDS AND DAMAGE BY THE COTTON LEAFWORM AND BOLLWORMS

F.F. SHALABY, E.F. ELKHAYAT*, A.A. HAFEZ AND E.A. KARES*
Plant Protection Dept., Fac. Agric. Moshtohor, Zagazig University , Moshtohor , Egypt
* Plant Protection Res. Institute, A R C, Giza , Egypt

ABSTRACT

Thirteen predaceous and six parasitoid adult species were counted and the damage caused by the cotton Leafworm and bollworms was estimated throughout 1992 cotton season in untreated cotton plots and those received three applications of the recommended chemical insecticides, Delfin (a bacterial insecticide of Bacillus thuringiensis var. Kurstaki) and their combinations. Chemical insecticides showed drastic effect on predator and parasitoid adult numbers (overall average of 37.5 and 65.6% reduction, respectively), Baythroid had the severest effect, followed by Cutabron and Empire. Adults of Scymnus sp. suffered the severest effect due to chemical insecticide applications.
Although the bioinsecticides Delfin had the least effect on entomophagous insect numbers, the heaviest damage due to S. littoralis and boliworms infestation was recorded. On the other hand, the three applications of the chemical and bio-insecticide combinations had less harmful effect on relative populations of beneficial insects than using the chemical insecticides alone, and gave satisfactory reduction in the damage caused by the mentioned pests. Consequently, the chemical and bio- insecticide combinations were recommended to control target pests to restore the entomophagous insects and obtain better insect pest control.

Key Words: Bioinsecticides, Entomophagous insects, cotton leafworm, bollworms.