Integrating sub-lethal heating with Brassica amendments and summer irrigation for control of Macrophomina phaseolina

Effects of varying intensities of sub-lethal heating were ascertained in improving the efficiency of Brassica amendments and summer irrigation on survival of Macrophomina phaseolina, a dry root rot pathogen. Sub-lethal heating (45 - 55 degreesC) of M. phaseolina infested dry soil reduced the viable propagules by only 12.8% in a period of 90 days. One summer irrigation without sub-lethal heating caused 33.9% reduction in M. phaseolina propagules, which improved to 43.3% when it was combined with 60 days of sub-lethal heating. Addition of the Brassica amendments to irrigated soil resulted in significant reduction (60.4 - 71.6%) in counts of M. phaseolina but this reduction improved (89.4 - 96.1%) when sub-lethal heating was combined with amendments. Mustard oil-cake (0.18% w/w) was found to be the most effective with reduction but a 94% inoculum reduction by mustard pod straw (0.36% w/w) was also achieved at 0 - 30 cm soil depth under similar conditions. Moderate heat level could not exert detectable weakening effect on M. phaseolina propagules. These results suggest a practical cultural control of soil-borne pathogens by combining sub-lethal heating, Brassica amendments with one summer irrigation.