Development of potato early die and its management with fumigants

Potato early die leads to premature plant death, reducing tuber yield and size profile. The soil borne fungi Verticillium dahliae and Colletotrichum coccodes and nematodes in the genus Pratylenchus are among the most important pests in the potato early die. The fungal pathogens infect during the spring and proliferate within the xylem elements and aerial parts of the potato plant. V. dahliae has been thought of as the more prominent pathogen in the complex; however, recent insights have suggested the importance of C. coccodes. Yield loss occurs every season from potato early die across North American potato production regions. Soil fumigation is the most effective management strategy for reducing these pests in the field and limiting yield losses. Metam sodium has long been the standard for soil fumigation in the Midwestern US, but chloropicrin has recently been increasing in use. Differences in fumigant performance, application conditions, and environmental effects lead to questions on which fumigant is optimum for a given field. This project works to describe the role each fungal pathogen plays throughout the growing season, and to determine the effect of each fumigant on the progression of early die, fungal colonization of plants, and yield. In the first year of this study a center pivot irrigated field with a history of early die was commercially split fumigated with chloropicrin and metam sodium. Chloropicrin reduced plant fungal colonization and protected more yield than metam sodium. The preceding year’s study expanded from these preliminary results, exploring the response of five commercially relevant russet cultivars to early die disease under both fumigants. Preliminary results show a consistent range of responses to early die of each cultivar under each fumigant. Outcomes from these field studies will aid in improving management of early die disease.