J U L Y / A U G U S T 2 0 1 7 POTATO GROWER 15 in the vines. Perham, Minnesota We have a single trial at this location evaluating fungicides for white mold control and the timing of those fungi- cides. Becker, Minnesota We have two trials in grower fields at this location. One trial is evaluating seed treatment and in-furrow fungicides for blemish control in red potatoes, and the second trial is evaluating blemish control of table potatoes by fall applied chloropicrin soil fumigation. NDSU Plant Pathology Dr. Guiping Yan, NDSU Dr Yan’s program focuses on studying plant diseases caused by plant-parasitic nematodes. Two field experiments are being conducted in 2017; one is at the Sand Plains Research Farm in Becker, Minnesota to identify the cause of pota- to emergence disorder, and the other is in Sargent County, North Dakota to evaluate management strategies for nematode control in potatoes. Brief summaries of these two projects are as follows. Project 1: Identify the cause of potato emergence disorder for infested fields in Minnesota. Potato emergence disorder is frequently observed in commercial potato farms in central Minnesota. The disorder has been studied for several years and the cause of the problem remains unknown. This problem occurs in sandy soils and has not been associat- ed with nutrient imbalances, herbicide injury or a pathogen. The symptoms include poor emergence and stunted plants often in patches or areas in the field. Soil-borne nematode pathogen, Pratylenchus penetrans, and fungal pathogen, Fusarium oxysporum, are commonly present in fields with this problem. It was therefore hypothesized that those pathogens may play a role as they both are important pathogens of potato. A microplot study is carried out in Becker, MN to evaluate the effects of the inoculation of these pathogens singly and in combination on emer- gence, growth and yield of the potato cultivar Red Norland. This experiment has thirteen treatments including P. penetrans (200, 800, 2,000 and 3,000 nematodes per 5 kg of soil) and F. oxys- porum (5, 10, 20, and 30 colonized bar- ley seeds per 5 kg soil) either inoculated individually or co-inoculated. This project is funded by the Minnesota Department of Agriculture through Minnesota Specialty Crop Block Grant Program. The overall purpose of this research project is to confirm the nema- tode and fungal species and to deter- mine whether the interaction between nematode and fungal pathogen causes potato emergence disorder. This project was started in May 2016 and will be completed by June 2018. Project 2: Chemical applications for control of corky ringspot disease of potato vectored by stubby root nema- tode. Corky ringspot disease on potato is caused by Tobacco rattle virus, which is vectored by stubby-root nematodes (Trichodorus and Paratrichodorus) and can result in up to 55% of potatoes from a harvest to be unmarketable. Dry brown necrotic arcs typical of the dis- ease were found on tubers of potatoes in Sprout Control Roger Brakke (701) 238-0765 FAX: (218) 863-4936 Clark Piepkorn (701) 780-9225 Cell: 218-779-4329 Midwest Potato Services