Brassica amendments and summer irrigation for the control of Macrophomina phaseolina and Fusarium oxysporum f. sp. cumini in hot arid region

Abstract

The combined effect of Brassica amendments (mustard oil–cake or mustard residue at 2.5 tons ha-1) and summer irrigation was tested for survival of Macrophomina phaseolina and Fusarium oxysporum f. sp. cumini and on the severity of dry root rot on clusterbean in the rainy season and on wilt of cumin in the subsequent winter season in the same field. Seed coating with a Bacillus sp., an antagonist bacterium against M. phaseolina, was also integrated with pod residues to improve control of dry root rot. The soil temperature of amended soil after one summer irrigation in June ranged from 38–44°C at 15-cm depth. These temperatures were 0.5–5°C higher than those recorded in unamended soil for the same period and 6–16°C higher when amendments were incorporated in July. A single summer irrigation led to a significant reduction in viable propagules of M. phaseolina, Fusarium oxysporum f. sp. cumini, plant mortality due to dry root rot in clusterbean and incidence of wilt on cumin from Brassica amendments, as compared with the application of amendments in July. A seed coating with Bacillus sp. alone was also effective, but integration with residues did not improve control of dry root rot. In general, amended soil held more soil moisture than unamended soil. These findings have a potential value for irrigated pockets in the hot arid zone of India as well as for many countries with the appropriate climatic conditions.