EFFECT OF SPRAYING SOME ORGANIC ACIDS ON CERCOSPORA LEAF SPOT DISEASE, YIELD AND QUALITY OF SUGAR BEET

Abstract

Sugar beet (Beta vulgaris var. saccharifera, L.) is one of the main economical sugar crops in Egypt. It is infected with Cercospora leaf spot disease, which is caused by Cercospora baticola Sacc. Fungs, which negatively affect the vegetative growth, yield and quality of sugar beet. The results obtained indicated that Cercospora leaf spot disease severity% and relative efficacy% were significantly reduced by spraying beets with 20 g/ L humic acid followed by 2 g/ L boric acid and 50 Mm/ L citric acid compared with the other treatments, in both seasons. Spraying of 1.5 g/ L boric acid treatment led to significant increase in most of traits where, it achieved thickest and heaviest tops and roots/plant and higher values of (chlorophyll a, b and carotenoids), sucrose, purity percentages, root and sugar yields/fed in both seasons, as compared to other humic acid levels. Application of 15 g humic/ L significantly affected endogenous phytohormones (gibberellins, auxins, cytokinin and abscisic) and gave the highest values of root diameter, fresh and foliage weights/plant, sucrose and purity percentages as well, sodium and potassium contents, root and sugar yields/fed in both seasons, photosynthetic pigments in leaves in 1st season only compared to the rest of the used levels of humic acid. Foliar application of 50 citric acid/fed increased root diameter, (foliage and fresh weights/plant), sucrose and purity percentages as well, root and sugar yields/fed in both seasons in comparison to that those plants sprayed with (30 and 40 mM/L) and the check treatment. Based on, the previously mentioned combination can be recommended to increase root yield and quality of sugar beet as well as to reduce Cercospora leaf spot disease severity.