الفهرس 
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Abstract
Potato crop is considered as one of the most important horticultural export also, edible and industrial food crop. In most recent years the EU has accounted for about 70-90% of Egyptian potato. Potato early blight disease occurs in most production areas to almost every year although it has a significant effect on yield only when frequent wetting of the foliage favours early and rapid symptom development. Estimating total annual crop losses due to any particular disease is difficult to do accurately. Values in the literature for crop losses due to early blight vary enormously from 5 to 78%( Waals et al. 2004; Pasche et al. 2004, 2005and El-Mougy et al. 2009).
Many control treatments were taken to minimize infection and decrease yield losses in potato growing areas. Intensive fungicide treatments decrease losses to less than 5%, also use of crop rotation, certified disease free seeds and resistant varieties are usually necessary in addition to fungicide sprays application to fully protect plants from early blight. Fungicide alternatives like inducers and biological control agents that have fungicidal effect on disease incidence and development ,are safety application and environmental pollution concern. There was a considerable interest in spraying bicarbonate solution which provided good control of several plant diseases (Karabulut et al. 2003; Smilanick et al. 2006). Biological control using either natural products or antagonistic microorganisms proved to be successful for controlling various plant pathogens in many countries (Papavizas and Lumsden 1980). It is still.