Growing some summer crops - preceding garlic - in heavily infested potted soil significantly reduced white rot disease (Sclerotium cepivorum) of garlic. Reductions in disease incidence obtained with sugarcane, roquette [ Eruca vesicaria] and sorghum as intercrops were 80.0, 73.3 and 66.7% of the control treatment, respectively. Reductions in disease incidence obtained with maize, squash, pepper, soyabean, cotton, sesame, cowpea and roselle ranged between 53.3 and 40.0%. Cauliflower, lucerne, broad bean, nigella, Egyptian clover, coriander and roquette grown in pots, as winter crops preceding garlic, exhibited 46.7-26.7% reduction in white rot disease. Intercropping cauliflower, coriander and roquette with garlic reduced the disease by 46.0-53.8%. Seedling root exudates of cauliflower, coriander and sorghum significantly reduced mycelial growth of S. cepivorum on PDA plates more than did radish and sugarcane. Cauliflower exhibited the highest reduction in mycelial growth, followed by sorghum and coriander. Ascending rates of cauliflower root exudates resulted in a higher reduction in fungus growth. Counts of fungi were significantly higher in soil of sorghum and roquette compared with sugarcane and coriander, while coriander rhizosphere yielded the highest density of fungi. Actinomycetes were detected in the rhizosphere at a highest count with coriander but were completely absent in the soil. Bacteria, in contrast, existed only in the soil where actinomycetes were completely absent. The highest count of bacteria was detected in sorghum soil. Actinomycetes inhabited soil only while bacteria and fungi existed in soil and rhizosphere of cauliflower, radish and garlic intercropped with the two crops. Cauliflower significantly increased counts of fungi and bacteria in rhizosphere when intercropped with garlic compared with those detected with garlic alone. Some recommendations are made.
