No abstract

Bio-agent compounds of Bacillus thuringiensis, Kurs. (Bactericide); Metarhizium anisopltiae, Metsch. (Fungicide) and biopolymer, chitosan exposed to gamma irradiation doses; 15, 30 and 60 Gy to purpose of potentiate the bio-agent efficiency against the cotton leaf worm, Spodoptera littoralis (Boisd.) treated as 4 th instars larvae by LC50 of tested bio-agent compounds singly or combined with gamma irradiation doses to investigate the histopathological changes in the integument, muscle, fat body and mid gut. Most of treatments especially gamma doses of 60 Gy singly or combined with bio-agent compounds caused thickening of outer cuticle fibrous layer in the integument of S. littoralis larvae. Also, hypodermis layer had swelling and necrosis in gamma treatments and M. anisopltiae or chitosan combined with 30 Gy treatments. Also, most of treatments caused appearance of fissure and breaking down of muscles into small parts. All the bio-agent treatments caused a noticeable destruction on the fat body cells as vacuolization of the fat cells and destruction of the fat body membranous sheath. Many deleterious effects in the mid gut of S. littoralis as destruction of columnar or hyperphesia cells lining mid gut, losses of brush border with increase of goblet cells. Dose of 60 Gy is considered the best dose used in the current study to potentiate the bio-agent effects on S. littoralis larvae compared with other gamma irradiation doses used.

The study was done in the laboratories of Bollworms, Leafworm and piercing & sucking Research Departments of Plant Protection Research Institute during 2010. The tested pests and the biocide, Protecto were exposed to gamma irradiation doses at National Center for Radiation Research and Technology, Egypt. Three tested insects were tested includes: pink bollworm, Pectinophora gossypiella (Saund.) newly hatched and fourth instar larvae, cotton leafworm, Spodoptera littoralis (Boisd.) 4 th instar larvae and the nymph & adult of cowpea aphid, Aphis craccivora (Koch). Insects were exposed to three doses of gamma irradiation, 150, 250 & 350 Gy. Also, the biocide compound, Protecto (Bacillus thuringiensis, Kurs.) was applied on the same pests to assess the insecticidal activity of Protecto in three combinations (Protecto +150 Gy, Protecto +250 Gy and Protecto +350 Gy). Data showed that the tested γ-irradiation doses of 150, 250and 350 Gy increased the newly hatched larval mortality of P. gossypiella to 52, 65 and 85% at zero day, respectively. While, it was reached to 100% kill at third day for 350 Gy and fifth day for 150 and 250 Gy. Larval mortality of P. gossypiella fourth instar was reached to 100% at eight and tenth days after radiation. Also, the larval mortality of S. littoralis fourth instar larvae was reached to 100% at tenth and twelfth days after treatment, respectively.While, A. craccivora adults and nymphs mortality was reached to 100% at zero day just after treatment. Generally, LC 50 , s on subjected insects treated with Protecto and exposed to gamma doses were lower than untreated Protecto.The aim of present work was to evaluate the insecticidal activity of the biocide Protecto in combination with γ-irradiation exposure against three key insect pests in laboratory.

No abstract

Cypermethrin, esfenvalerate, chlorpyrifos and Bacillus thuringiensis, Kurs. were tested against the cotton leaf worm, Spodoptera littoralis (Boisd.) treated as 4 th instar larvae. In addition, LC 50 , s of tested compounds were applied on S. littoralis larvae to investigate the ultra structural changes in the integument, muscle, fat body and mid gut of alive and dead larvae. Meanwhile, the nerve cord sections were investigated for alive larvae only. All investigations were done by light and electronic microscopes.Cypermethrin was the most potent compounds against S. littoralis larvae, followed by esfenvalerate, chlorpyrifos and then B. thuringiensis that had the least toxicity on the cotton leaf worm compared to other tested compounds.Ultra structural investigations showed that cypermethrin caused thickening of outer cuticle fibrous layer in the integument of S. littoralis larvae. Also, hypodermis layer had swelling at the same treatment and necrosis in other treatments. In addition, all the treatments caused appearance of fissure and breaking down of muscles into small parts. While, all tested compounds except B. thuringiensis caused swelling in the integuments of dead larvae compared to control. On the other hand, B. thuringiensis caused drastically necrosis in the integument and hypodermis layers of dead larvae. All the compounds caused a noticeable destruction on the fat body cells as well as vacuolization and destruction the fat body membranous sheath. Many deleterious effects in the mid gut of S. littoralis as destruction of columnar or hyperphesia cells lining mid gut, losses of brush border with increase of goblet cells. Mid gut of died larvae had the highly destruction as affected by cypermethrin treatment. Meanwhile, other treatments caused shrinking in mid gut parts and necrosis in another parts. Neurosecretory cells of S. littoralis larval nerve cord had shrunk and dwarfed in cypermethrin, chlorpyrifos and B. thuringiensis, while; it had swelling in esfenvalerate treatment. Also, nucleus and nerve cells were disappeared partly in the most treatment compared to control.