Root rot: Rhizoctonia bataticola (Pycnidial stage: Macrophomina phaseolina)

Symptom

• Germinating seedling shows black lesions on hypocotyls, girdling of stem and death of seedlings.
• Affected basal stem becomes dark with bark shredding and sclerotial bodies present in the shredded bark.
• The entire root system gets rotted, plants dried and the affected plants can be easily pulled out.

• The disease is soil-borne and the pathogen can survive in the soil as sclerotia for several years.
• Primary spread is through soil borne sclerotia.
• Secondary spread through sclerotia disseminated by irrigation water, implements, heavy winds and other cultural operations.

• Dry weather following heavy rains.
• High soil temperature (35-390C), low soil moisture (15-20 per cent).
• Cultivation of favourable hosts like vegetables, oil seeds and legumes preceding cotton and wounds caused by ash-weevil grubs and nematodes.

• Remove and burn the infected plant debris in the soil after deep summer ploughing.
• Apply farm yard manure @4 t/ac or neem cake @ 60 kg/ac.
• Take up sowing in the first week of April or last week of June.
• Adopt intercropping with sorghum or moth bean (Phaseolus aconitifolius) to lower the soil temperature.
• Treat the acid-delinted seeds with Chlorothalonil at 4 g/kg of seed
• Treat seeds with Bacillus subtilis (10g/kg) or Trichoderma asperellum @ 4 g/kg.
• Treat seeds with Tetraconazole 11.6% w/w (12.5% w/v) SL @2 g /kg of seed Carboxin 37.5% + Thiram 37.5% WS @2.5g/ kg of seed
• Apply Trichoderma asperellum @ 1 kg/ acre, twice in the soil during sowing and 90 DAS . Multiply 1 kg of T. asperellum in 100 kg of Farm yard manure for 15 days before application
• Spot drench with Carbendazim @ 1 g/l or Trifloxystrobin + Tebuconazole @ 0.75g/l at the base of affected plants and surrounding healthy plants