CONTROL OF THE ROOT ROT DISEASES OF WHEAT USING FUNGICIDES ALONE AND IN COMBINATIONS WITH SELENIUM

Five fungicides (tebuconazole, fludioxonil, iprodione, azoxystrobin and flutolanil) were evaluated separately or in mixtures with the antioxidant (selenium) against Fusarium graminearum and Rhizoctonia solani which causing root rot diseases of wheat. Depend upon EC50 values of the tested fungicides, the in vitro studies showed that the descending order of fungicidal activity against F.graminearum growth was as follows;fludioxonil> tebuconazole > iprodione > azoxystrobin > flutolanil, while it was flutolanil >fludioxonil> tebuconazole > iprodione > azoxystrobin against R. solani growth.The two fungi tolerated high concentration of selenium. Interestingly, the fungitoxic activities of the tested fungicides were greatly increased by adding selenium to the fungicide- amended medium. In greenhouse trials, the fungicides were applied at rates of 1.5 and 3.0 g /kg seeds, while selenium was applied at 10 and 20 μg / ml (as seed treatments) alone or in combinations with fungicides for controlling root rot diseases. The results showed that all fungicides treatments significantly reduced diseases incidence and increased emergence and plant stands. Generally the addition of the antioxidant (Se) at 20μg / ml to the higher rate (3.0 g/kg seeds) of each fungicide caused significant reduction of the pre- and post- emergence damping off and subsequently increased plant survivals. However, the addition of Se to the low rate of each fungicide gave satisfactory fungicidal action as well as minimizing the environmental pollution.