12 IREC Farmers' Newsletter No. 198 — Spring 2017 BLACK ROOT ROT THREATENS PROFITABLE COTTON PRODUCTION Integrated disease management is the key to prevent the profitability of cotton being reduced by the seedling disease, black root rot. PHOTO: Virginia Tapscott l  Black root rot delays successful establishment of cotton crops, and makes seedlings more susceptible to other soil-borne diseases. l  Summer flooding of fields for 30 days when daytime temperatures are above 30°C is a recognised treatment of the disease in the USA. This could be an option for some growers, especially those with rice suitable soils and layouts. l  The best way to manage the disease is an integrated approach to black root rot management, which includes rotations of crops that do not host the disease, fallows, biofumigant crops and avoiding waterlogging during crop establishment. Black root rot fungus together with other seedling diseases can result in plant stand losses of 30% or more in new cotton crops. Kieran O’Keeffe Regional Extension Officer CottonInfo Southern NSW Andrew Watson Plant Pathologist NSW Department of Primary Industries, Yanco Agricultural Institute BLACK root rot, caused by the soil fungus Thielaviopsis basicola, was first observed in Australian cotton in 1989. It has a wide host range causing disease in over 137 species of plants. The fungus survives for long periods in the soil as resistant resting spores. Infection of cotton is favoured by soil temperatures below 20 °C, which is normal at planting time. Research in the USA has shown that severe disease symptoms result when the population of the black root rot fungus reaches 100 spores QUICK TAKE