Experiments on soil drenching with fungicides against take-all in wheat

In short term pot experiments benomyl, iprodione and KWG 0599 applied as soil drenches in several types of soil significantly suppressed take-all symptoms from inoculum placed just below wheat seeds planted 1×5 cm deep, and in sand but not other soils when seeds were 5 cm deep. Benomyl was, however, effective against inoculum below seed planted 5 cm deep in a loam-sand mixture when the drench contained an alcohol ethoxylate surfactant. Computer simulations of fungicide distributions in the soils correlated well with disease control observations. In long term outdoor pot experiments two drenches with benomyl (without surfactant) controlled disease significantly for at least 3 months against inoculum placed 15 cm deep. The significance of these results for the practical control of take-all by fungicides is discussed.