Biological Control and Re-curing of Sweet Potato Roots as Alternatives for Managing Rhizopus Soft Rot

View the project final report

Commodities

• Vegetables: sweet potatoes

Practices

• Pest Management: biological control, integrated pest management, physical control

Sweet potato storage is limited by several postharvest diseases, of which, Rhizopus soft rot (RSR), caused by the wound-dependent fungus Rhizopus stolonifer is most devastating. Roots are normally cured following harvest to heal wounds, thereby minimizing the risk of RSR infection in storage. During packing however, sweet potato roots are treated with the fungicide dicloran (Botran). Increasing concerns about pesticide residue on the sweet potato roots poses the need for alternative ways of managing RSR. Even though the potential of using biological control or re-curing roots has been demonstrated by a few authors, there is need to research further to determine the optimal application times and determine if combining these methods will improve the level of control. The objectives of this two-year project are, therefore, to evaluate the effectiveness of integrating improved resistance to RSR with the biological control product, P. syringae strain ESC-10 (Bio-Save 10LP), applied either as an overhead spray or as a dip to sweet potato roots; and re-curing sweet potato roots for different periods on the incidence of RSR. These practices will be evaluated individually and in combination. Several advanced breeding lines with greater resistance to RSR will be compared with predominant commercial cultivars Beauregard, Bayou Belle, Orleans and Hernandez. At 120 and 150 days after harvest, sweet potato roots will be artificially wounded and inoculated, and evaluated for RSR incidence for 10 days. The expected outcome is the development of an integrated pest management (IPM) strategy for managing RSR using more sustainable methods, to meet the needs of all markets.

• To evaluate the effectiveness of the biological control product, P. syringae strain ESC-10 on the roots of five sweet potato cultivars with varying resistance at the recommended label rate and applied either as an overhead spray or as a dip.
• Assess the effects of re-curing at different re-curing periods (0,4,8, or 24 hours after wounding), up to five sweet potato cultivars with varying resistance, inflicted with two wound types on the incidence of RSR.
• Assess the combined effects of the biological control product Bio-Save 10LP, applied to sweet potato roots of varying RSR resistance during packing, and followed by re-curing on the incidence of RSR.