Abstract

Powdery mildew disease is one of the most deleterious diseases affect wheat reflecting in serious grain yield losses. Control of such disease is important in view of the wheat is the main crop for population consumption in Egypt. Therefore, this study was conducted during 2019-20 at Kafr-El-Dawar region, El-Behira governorate, Egypt to evaluate the suppressing effect of some organic acids applied as foliar spray against disease severity of wheat powdery mildew caused by Blumeria graminis f. sp. tritici under field conditions. Field experiments performed with cultivation of three wheat cultivars at two different fields on two successive sowing dates. During the growing season, wheat plants were sprayed with salicylic, oxalic, benzoic, humic and malic organic acids and the fungicide Topsin M70 twice with one-month interval started at one month after seedlings emergence. No disease symptoms were observed for all cultivars which sown early. The wheat cultivar Giza 171 showed the lowest disease severity (6.2 -7.8%) followed by Misr 1 (7.5 -11.5%) and Gemmiza 12 (20.0 -30.8%) at all applied treatments. High suppressing effect on the severity of powdery mildew was recorded at wheat plants sprayed with salicylic acid (7.8, 7.5 and 21.7%) followed by humic (6.2, 8.3 and 24.2%) and malic acids (6.7, 8.3 and 20.0%) compared with oxalic acid (7.0, 11.5 and 30.8%) and finally the fungicide Topsin M70 (16.3, 23.3 and 27.0%), respectively. An opposite trend for the increase in produced grains yield in parallel with reduction in disease severity was observed. The present results demonstrated that early sown date, suitable resistant varieties in addition to utilize plant resistance inducers are important factors for escaping from disease infection and subsequently its development.