Effects of plant residue, soil characteristics, cotton cultivars and other crops on fusarium wilt of cotton in Australia

Abstract

The incidence and severity of fusarium wilt of cotton in glasshouse trials increased when levels of plant residue in the soil were increased by the incorporation of whole cotton plants (6-week-old seedlings dried out for a further 6 weeks) into the soil. In non-residue-supplemented potting mix, disease incidence was <50%, but ranged from 74 to >90% in residue-supplemented potting mix. The disease was significantly affected by soil microflora and soil type, but not affected by soil pH in the range 4.0–8.5. Although the same amount of inoculum was added to both autoclaved and untreated soils, the disease was less severe in autoclaved soils than in untreated soils regardless of soil type. Among the 4 clay soils investigated, the disease was less severe in a grey sandy clay and a brown heavy clay than in a dark grey heavy clay. Compared with the soils collected at the end of the 1995–96 growing season, the disease became more severe in the soil of plots planted to the most susceptible cotton cultivar Siokra 1-4, but less severe in the soil of plots planted to the less susceptible cotton cultivar DP90 at the end of the 1996–97 growing season. However, no significant differences were observed in the soil of plots planted to cotton cultivar Siokra L22, sorghum, maize or soybean.