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This study was carried out to evaluate the effect of ammonium sulfate, calcium chloride, potassium dibasic phosphate and sodium carbonate on inhibiting mycelial growth of Alternaria alternate (Fr.) Keissler, Helminthosporium sp., Stemphylium botryosum Wallroth, and Curvularia lunata (Wakker) Boedijn isolated from lettuce (Lactuca sativa Folium.) leaves. The sodium carbonate and ammonium sulfate strongly inhibited mycelial growth and spore germination. Potassium dibasic phosphate and calcium chloride inhibited mycelial growth to a less extent. Sodium carbonate (25mM) decreased mycelial growth of A. alternate by 58.9%, Helminthosporium sp. by 58.8%, S. botryosum by 78.5% and C. lunata by 40.0%. The folpet fungicide used variably decreased growth of fungi in a range varied between 43.5% and 87.5% at 5ppm concentration. The effective concentration (EC50) figures indicated that sodium carbonate and ammonium sulfate caused more inhibition to A. alternata, Helminthosporium sp., S. botryosum and C. lunata. Lower concentration of potassium dibasic phosphate and calcium chloride showed lower effect. In general, the most effective chemicals used to control lettuce foliar diseases were sodium carbonate, ammonium sulfate, calcium chloride and potassium dibasic phosphate that decreased leaf spot severity. Sodium carbonate had a higher inhibiting activity against foliar diseases of lettuces. Expression of defense related enzymes involved in lettuce induced tolerance against infection was emphasized. The greater hydrolysis of plant cell walls by A. alternata, C. lunata, Helmithosporium sp. and S. botryosum was attributed to greater of polyglacturonase (PG) secretion.

Cabbage is one of the most widely cultivated vegetables in Egypt; Fusarium wilt causes significant crop loss in quantity and quality of most vegetable crops. The most frequency and isolated fungus from cabbage roots growing at Faquose District, Sharkia Governorate, Egypt was Fusarium oxysporum, followed by Verticillium albo-atrum. As for pathogenic activities of Verticillium albo-atrum and Fusarium oxysporum isolates on cabbage plants (cv. Balady), Fusarium oxysporum isolate No.5 gave the highest wilt disease severity. Host range of the tested Fusarium oxysporum isolate 5 revealed that cabbage (cv. Balady) was the only infected host. Field experiments were conducted to study the effect of Topsin M70%, Microbin, Rhizobactrin, and Weed-Max (blue-green algae extracts in powder phase) and Oligo-X algae (blue-green algae extracts in liquid phase) on vegetative growth (head diameter and stem height), total yield and wilt disease severity on cabbage (cv. Balady), during the two winter growing seasons of 2015 and 2016 in Sharkia Governorate at Faquose District. Results showed that both head diameter and total yield were increased by Topsin M70% and Microbin application followed by Weed-Max as well as Oligo-X, but the lowest one was Rhizobactrin compared with control. Also, wilt disease severity was decreased without significant effect on stem length. Regarding the effects of applied treatments on biochemical changes in cabbage plants (cv. Balady) under field conditions, all tested treatments reduced the activities of polygalacturonase (PG) and cellulase (CX) enzymes as well as, increased total phenols and total chlorophyll compared with control. In this respect, Topsin M70% and Microbin followed byWeed-Max as well as Oligo-X were the most effective treatments in reducing the activities of PG, CX and increased total phenol contents compared with Rhizobactrin treatment and control.

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Downy mildew of cucumber is caused by the fungus-like pathogen Pseudoperonospora cubensis (Berk and Curtis), which causes loss in the yield in Egypt especially under protected cultivation where low temperature and high humidity are prevalent. The efficiency of two Bio-control agents i.e. T34 (Trichoderma asperellum, 10 9 spore/cm 3 ) and Bio-Cure-B (Pseudomonas fluorescens, 10 8 spore/cm 3 ) as well as three resistance inducing chemicals (RICs), i.e. potassium dihydrogenphosphate (K 2 HPO 4 ), salicylic acid (C 7 H 6 O 3 ), and potassium nitrate (KNO 3 ) were evaluated for controlling cucumber downy mildew under greenhouse and plastic house conditions. Greenhouse experiment data revealed that, spraying cucumber plants with either biocontrol agent or tested RICs two times i.e. 5 days before and/or nine days after artificially inoculated by the P. cubensis significantly reduced percentage of disease severity, meanwhile plant length and foliage fresh weight were increased in comparison with control treatments. The treatments increased the activity of peroxidase, β-1,3glucanase, beside increase in total carbohydrates and total phenolic contents. Under plastic house, all tested biocides and/or RICs either alone or double combinations caused significant reduction in disease severity associated with significant increment in some growth parameter of cucumber plants (plant length and fruit yield) when compared with control treatments in both seasons. However, application of tested RICs mixture with tested biocides was more effective in this regard than the only application of them individually. In this respect, tested biocides were also more efficient than resistance inducing chemicals (RICs).