1. ENVIRONMENTALLY SAFE COMPOUNDS IN
CONTROLLING SUGAR BEET POWDERY MILDEW
Dr. Ayman M. H. Esh (Senior Researcher) Department of Sugar Crops Pests and Diseases Research, Sugar Crops Research Institute, Agricultural Research Center - Giza, EGYPT.
Sugar beet Powdery mildew disease (Fig.1) caused Erysiphe betae (Vanha) is a serious disease in Egypt, occur during Mars, April and May during the repining stage. The fungal foliar disease resulting in sugar yield losses of up to 30%
With the recent concern regarding pesticide residues on plants, there is a need for alternative disease-management practices that will reduce risk to the environment.
Dr. Mohamed Sameh Shalaby, Assistant Professor of Plant Pathology, Department of Plant Production, Sufficient Productivity Institute, Zagazig University, Egypt.
Six Calcium Salts, Ca-sulphate, Ca-hydroxide, Calcium-disodium-ethylenediaminetetraacetate; Ca-chloride, Ca-polysulfate and Ca-carbonate.
as well as Salicylic acid and 3-aminobutyric acid were evaluated for protective and curative effects in controlling the disease in greenhouse and there effect on the fungus conidio spores in the laboratory.
Fig. 1: Symptoms of sugar beet powdery mildew (Erysiphe betae) on sugar beet leaves.
A: healthy leaf. B: infected leaf. C. magnification of infected area showing the powdery appearance of the fungus mycelium on the surface of the leaf and the ascocarps as a little dark dots. D. a magnified ascocarp.
Mature leaf area diseased (MLAD) was calculated according to the severity rank and formulas suggested by Paulus et al., (1982) as follows:
Average rating per leaf: R' = [N (R°)] / ΣN
Average of treatment: R'' = Σ R' / number of R'
Mature leaf area diseased (MLAD): = 100{ sine [R'' (18°)]}2
Where:
N = number of infected leaves.
R° = severity rank as shown in fig. 1.
Severity rank (0-5) for powdery mildew on sugar beet leaves according to Paulus et al., (1982).
Main effect of spraying sugar beet plants with three concentrations (4000, 8000 and 1200 ppm) of six calcium salts and three concentrations (50, 100, and 200 ppm) of Salicylic acid and 3-aminobutyric acid twice before infection on the % Mature leaf area diseased (MLAD) under greenhouse conditions.
Mature leaf area diseased (MLAD) % a b d c de
Mature leaf area diseased (MLAD) a b
Main effect of spraying sugar beet plants with three concentrations (4000, 8000 and 1200 ppm) of six calcium salts and three concentrations (50, 100, and 200 ppm) of Salicylic acid and 3-aminobutyric acid after 3 days from inoculation with powdery mildew conidio spores on the % Mature leaf area diseased (MLAD) under greenhouse conditions.
Mature leaf area diseased (MLAD) a b %
Mature leaf area diseased (MLAD) a b c d cd
Effect of spraying sugar beet plants with calcium compounds before inoculation.
A and E show the severely infected control treatment
B,C and D show the effect of calcium chloride application at 4000, 8000 and respectively.
Effect of tested calcium compounds as well as salicylic acid and Aminobutaric acid at 3 different concentrations on Erysiphe betae conidio spores after 24 hours incubation in 100% RH moist chamber at 26°C . a b d c
Different germination stages of Erysiphe betae conidio spores under the stress of Ca salts, 3-aminobutyric acid and salicylic acid after 48 hours incubation in 100% RH moist chambers. A and B showing ingeminated spores, C,D, and E showing different types of germination, the arrows indicating the germination tubes. (Photographs taken by a CCD camera attached to light microscopy)
Ayman Esh, 2008