Submitted to: Stored Grain Insect and Pest Management Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 1, 1999
Publication Date: N/A
Interpretive Summary: There are a number of potato storage diseases that can cause catastrophic losses. Late blight, Pink Rot, Leak, and Bacterial Soft Rot alone or in combination must be managed by the grower without effective chemical controls. Although protectant fungicides can reduce foliar late blight to manageable levels in the field the tuber rot phase of the disease eis often poorly controlled. This presentation describes ways to avoid tube infections to start with in the field. This can be done with careful attention to late season irrigation and vine killing procedures and by minimizing damage to tubers at harvest. Control of temperature, humidity, and ventilation can be used to stop spread of these rots in the storage. General guidelines for storage rot management are outlined.
Technical Abstract: The new strains of late blight that have appeared in North America since 1994 require new management approaches. Since they are resistant to the fungicide, metalaxyl, that has been relied on to control the disease for the past 20 years a more intensive protectant fungicide program must be used. All major varieties grown in North America are susceptible to the disease although there are differences in susceptibility-particular to the tuber rot phase of the disease. Russet Norkota is particularly susceptible to both the foliar and tuber phase of the disease Ranger Russet, Shepody, and Russet Burbank are susceptible to the foliar phase but Russet Burbank is somewhat less susceptible to the tuber rot. None of these major varieties has enough resistance to be effective in a management program either in the field or in storage. A timely fungicide program must be followed in the field. Vines must be thoroughly killed before harvest. Storages must be carefully monitored and if late blight and associated rots are found then temperature, humidity, and ventilation must be optimized for rot control. Once infection exceeds 5% of tubers in storage long-term management of the rot is problematic. Efforts must be made to market the potatoes as quickly as possible. Maximum ventilation with reduced relative humidity and and reduced temperature (70% RH and 40 F) for non-processing potatoes will extend the storage time. Pink Rot, Leaks, Bacterial Soft Rot, and Freezing injury need to be managed in the same way.