Downy mildew caused by Pseudoperonospora cubensis (Berk. and Curt) Rostow is a major disease of cucumber (Cucumis sativus L.) in Egypt. The current study was carried out in Fayoum, Ismailia and Kafr Elsheikh Governorates in summer and fall during of 2018 and 2019 seasons. The effect of some whither parameters on downy mildew was studied. Temperature, relative humidity, disease severity and their relationships were determined. Five fungicides Previcur N 72.2 SL, Veulet 80 WP, Previcur Energy 840 SL, Infinito 68.75 SC and Profiler 71.1 WG, were used for the disease control. Final disease severity (FDS), area under disease progressive curve (AUDPC) and fungicides efficacy were measured and analyzed. Scanning electron microscope was used for histopathological studies. Fresh, dry weight and the average number of fruits/plant and fruit yield/feddan (ton) were recorded. Kafr Elsheikh recorded the lowest average temperature, being 23.8°C during the two growing seasons followed by Ismailia and Fayoum, being 25.2°C and 26.9°C, respectively. Kafr Elsheikh, also recorded the highest average of relative humidity, being 53.3% during the two growing seasons followed by Fayoum and Ismailia, being 52.9% and 51.9%, respectively. The same trend was observed for disease severity that recorded the highest average in Kafr Elsheikh, Ismailia and Fayoum 36.2, 31.45 and 30.9%, respectively during the two growing seasons. On the other hand, the lowest average temperature and the highest average of relative humidity were recorded in

http://eajbsf.journals.ekb.eg/ Comparison between the Effectiveness of Certain Insecticides and Entomopathogenic Nematodes Against Tortoise Beetle, Cassida vittata (Vill.

The development of resistance and biochemical mechanism of the cotton leafworm, Spodoptera littoralis (Boisd.), to five insecticides (chlorpyrifos, profenofos, cypermethrin, spinosad and flufenoxuron) were studied in the laboratory. The parent strain of S. littoralis was collected from El-Fayom Governorate at the cotton season 2005 and reared under laboratory conditions for seven generations, then subdivided into five sub-strains, three of them were selected by chlorpyrifos, profenofos and cypermethrin for fourteen generations and two were selected by spinosad and flufenoxuron for twelfth generations at LC30 level. Selection pressure in all experiments was carried out on 4 th instar larvae by the leaf dipping technique. At the end of selection, the results indicated that the resistance ratios (RR) were 16.30-, 40.23-, 1070.42-, 145.14-and 8.24-fold for chlorpyrifos, profenofos, cypermethrin, spinosad and flufenoxuron, respectively, compared with the parent strain. At the end of selection pressure, detoxifying enzyme assays revealed that the α-esterase activity levels for such insecticides were 4.64, 4.67, 3.10, 3.40 and 1.24 times, respectively, higher than in the parent strain whereas those of β-esterase activity were 4.16, 4.07, 3.11 and 3.64 times for chlorpyrifos, profenofos, cypermethrin and spinosad, respectively, higher than in the parent strain, on the contrast the β-esterase activity for flufenoxuron was 0.96 time lower than in the parent strain. In addition, the levels of glutathione S-transferase (GST) activity at the end of selection with these insecticides were 6.62, 6.43, 2.11, 4.69 and 1.32 times, respectively, higher than in the parent strain. The results showed a correlation between the activity of both non-specific esterases (α-and β-esterases) and GST and resistance level to the tested insecticides. The results, also, indicated that the broad spectrum of insecticide observed in the field populations was due to multiple resistance mechanisms, including their increased detoxification. Finally, the rapid assessment of esterases and GST activities may be useful for monitoring resistance to these insecticides in S. littoralis. Therefore, differential levels of such enzymes could likely be used to detect the development of resistance during the early stages of insecticide resistance in the field.

The side effects of azoxystrobin (Amistar, 25% SC) and tebuconazole (Toledo 43% SC) fungicides on some biological aspects of Egyptian cotton leaf worm (ECLW) (Spodoptera littoralis, Boisd.) were investigated in comparison with the untreated control under laboratory conditions. The fourth instar larvae were fed for 24 hrs on castor bean leaves (Ricinus communis L.) treated with different concentrations of the tested compounds. Food consumption was measured regularly throughout the feeding tests until pupation. The results clearly indicated that the two fungicides reduced the weight consumed leaves larva-1 and decreased the feeding ratio. The azoxystrobin fungicide was more effective than tebuconazole especially at higher concentrations. Both compounds reduced larval weight and increased larval mortality and larval durations (days). Furthermore, reduced pupation % and adult emergence, and increased pupal durations. These compounds reduced reproductive parameters of adults (fecundity and fertility) and increased sterility %. The longevity of males and females was reduced. The present study revealed that, in all cases, the toxic effects of azoxystrobin and tebuconazole on some biological aspects of the Egyptian cotton leaf worm were proportionally increase with the increase of the concentrations. The results clearly indicated that the azoxystrobin fungicide was more effective than tebuconazole on Egyptian cotton leaf worm (ECLW).