AbstractPOTATO NEMATODE RESEARCH: WITH SPECIAL REFERENCE TO POTATO-EARLY DIE, CORKY RINGSPOT AND SOIL ENZYMESByLoren George WernettePotato production faces numerous challenges three of these include Potato-Early Die (PED), Corky Ringspot Disease of Potato (CRSD), and soil quality issues. This thesis consists of three chapters: 1) Impact of Alfalfa on Soil-Borne Enzymes in Potato Systems. 2) Vertical Distribution of Paratrichodorus pachydermus, Pratylenchus penetrans (Nematoda), and Verticillium dahliae (Mycota) in Michigan Potato Systems. 3) Soil Fumigation Guide. Soil quality was evaluated comparing soil enzyme activities associated with fields that had been in alfalfa for ten years in two year potato rotations with corn. We found that the alfalfa rotation had higher enzyme activities for phosphatase and tyrosine aminopeptidase. We also found that the mineralization rate of carbon was significantly higher in the alfalfa system, compared to the potato rotation. The nematode pathogens for CRSD and PED were evaluated to determine the depth at which the highest population density of Pratylenchus penetrans, Paratrichodorus pachydermus, and Verticillium dahliae were found in a potato system. We found that the majority of P. pachydermus was found below, a 30 cm soil depth in September. We also found that P. penetrans was found most commonly in the upper 30 cm of the soil. When targeting the virus vector, P. pachydermus. Fumigant and non-fumigant nematicides were tested. As the amount of active ingredient of the chemicals increased, however, the percent of CRSD symptom expression in the tubers decreased. We also showed that there was no increase in symptom expression during tubers storage.
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