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Abstract
SUMMARY
Cotton is the major economic crop in Egypt. During the growing season, the plants are attacked by several pest insects during its different development stages of growth. Lepidopteran pests (Pectinophora gossypiella, Earias insulana and Spodoptera littoralis) are considered to be important and key insects causing a lot of damage and loss of cotton yield. The extentive use of the conventional insecticides creating a lot of problems such as the insects resistance to insecticides and environment pollution. So, it is necessary to use particular insecticides such as Insect Growth Inhibitor and bio-insecticides to aggrandize role of the naturally enemies (predators and parasitise) and for obtaining less environmental pollution and the hazards to human.
The field experiments of the present study were carried out at El-Bassiuony Farm at Abo-Homos, El-Bihaeira Governorate, Egypt, during the subsequent cotton seasons of 2003 and 2004. The objectives of this contributional study were initiated to evaluate the combined role of the natural enemies by using the parasitoid Trichogramma evanescens in reducing cotton infestation by some lepidopterous pests through the application of insect growth inhibitors and bio-insecticides compared with achemical insecticide as standard and determining the effect on the yield characteristics.
The obtained results can be summarized as follows:
1. Field Application of certain IGIs, B.t based formulations and a chemical insecticide (Chlorpyrifos) against Spodoptera littaralis.
1.1. The growing season of 2003:
The detected number of S. littaralis larvae before the application of tested compounds was ranging between 678-708 larvae/ 25 cotton plants. Overall 14days post-treatment, the number of larvae in those plants treated with Clorpayrifos was sharply decreased to 4 larvae / 25 plants. It was noticed that the IGI compound Chlorfluazuron was as effective as the chemical insecticide Chlorpyrifos giving 6 larvae / 25plants after 14 days post-treatment. In this respect it could be said that Chlorpyrifos can be replaced by Chlorfluazuron and to be used since the chemical insecticides might contaminate the environment. Lufenuron (an IGI) was proved to as effective as Dipel-2x® (Bt) against S. littaralis larvae giving a number of 24 larvae/25 plants after 14 days post-treatment, while Dipel-2x® gave 26 larvae / 25 plants. The least effective compound was Agerin® (Bt) which gave 146 larvae / 25 plants compared with the other tested compounds and control (untreated check) (530 larvae/25 plants).
2.1. The growing season of 2004: