Four trials of disease management, i.e. varietal resistance, methods of irrigation, antioxidants and fungicides were tested to evaluate their role in managing okra powdery mildew caused by Erysiphe cichoracearum DC.
The four tested okra cvs. were liable to infection by the disease.. However, Japanese cv. )resistant) showed the lowest infection and gave the highest fruit yield followed by Hendi cv. (moderately resistant).Meanwhile, both Balady Red and Balady Green cvs. were highly susceptible and gave the lowest fruit yield.
Methods of irrigation , i.e. drip , flood and spray caused significant variations in the severity of the disease. Spraying method resulted in high reduction in the disease with great increase in fruit yield compared to the other two methods.
All the tested antioxidants, i.e. ascorbic acid, citric acid, manitol and salicylic acidcaused significant reduction in the disease severity with significant increase in the fruit yield compared to the control treatment. In addition, salicylic acid was the most efficient one in this regard followed by citric acid then ascorbic acid. Meanwhile, manitol showed the lowest effect.
All the tested fungicides, i.e. Karathane, Rubigan, Sumi-8, Thiovit Jet, Topas and Vectra caused significant reduction in the percentages of the germinated conidia of E.cichoracearum. In addition, Topas followed by Sumi-8 then Rubigan and Vectra (systemic fungicides) caused the highest inhibitory effect. Meanwhile, Thiovit Jet followed by Karathane (non-systemic fungicides) showed the lowest effect.
Spraying okra plants with the tested fungicides caused significant reduction in the severity of the disease compared to control treatment. The reduction in the disease severity showed, to some what, the same trend of the effect of tested fungicides on conidial germination. This reduction in the disease was reflected on the obtained fruit yield.