Sustainable management of moko and bugtok diseases of banana

Moko and bugtok diseases of banana are caused by Ralstonia solanacearum (Smith) Yabuuchi et al. In the Philippines, the two diseases may seem different because moko is observed more often affecting the export variety 'Cavendish' with wilt symptom while bugtok is very common in cooking bananas like 'Saba' and 'Cardaba' as fruit pulp discoloration. The authors conducted cross-inoculation experiments under field conditions to better understand the relationship of our endemic bugtok strain with the moko strain of Ralstonia solanacearum Race 2. Symptom expression was affected by the age of the plant, cultivar, mode of transmission and strain of R. solaacearum. Both 'Cardaba' and 'Cavendish' cultivars developed wilt or moko symptoms when inoculated with either moko or bugtok strains. 'Cardaba' had the ability to recover from wilting when inoculated at 3 and 6 months after transplanting (AT). Late inoculation at 9 months AT of 'Cardaba' resulted inv ery slow increase in wilt incidence over time but reached to almost 100% at maturity. High incidence of wilt occurred in 'Cavendish' 2-3 weeks after inoculation especially when the bugtok strain was used. All plants that survived had several degrees of fruit pulp discoloration or bugtok symptoms. The 'Cardaba' fruits had a higher number of fingers discolored per bunch. Infection via the inflorescence did not result in wilt symptom. Fruit pulp discoloration in both cultivars resulted when bacteria were sprayed on male or female flowers and when bacteria were injected at the base of the flower bud before emergence. 'Cardaba' had higher bugtok symptoms than 'Cavendish' while the bugtok strain caused higher frujit pulp discoloration than the moko strain across both cultivars. Management strategies for moko and bugtok diseases should be similar if infection is via wounds created in the pseudostem or corms whether the variety is 'Cavendish' or 'Cardaba'. Disinfection of tools used in desuckering, debudding or deleafing, use of disease free planting materials, clean culture to remove weeds and volunteer plants should minimize incidence of wilt or moko symptoms. If present int he farm, early detection and swift destruction of infected plants and mats should be done. Instead of the usual rice hull burning, burning of standing moko infected plants could be alternative. By doing so, a high population of bacteria from plants is not allowed to ooze out into the soil. Planting of sorghum during the fallow period was found ineffective. For bugtok, protecting the female and male flowers by early bagging will prevent insects from transmitting R. solanacearum. Since the cooking bananas are very tall and bagging may be impractical, the combination of sanitation, disinfection of cutting tools and removal of male buds as soon as false hands appear should result in good control.