Seasonal Population Dynamics of the Plant-parasitic Nematode, Anguina pacificae on Golf Course Putting Greens in California

The plant-endoparasitic nematode Anguina pacificae is presently one of the most destructive pests of Poa annua in Northern California, causing stem galls at the base of tillers in this annual bluegrass, resulting in yellow or brown patches and irregular surfaces on golf course putting greens. The objective of the study was to investigate the population dynamics of A. pacificae on two golf course putting greens in California (‘Poppy Hills’ and ‘Olympic Club’) over ca. 16 months. For most of the sampling period, the number of galls and nematode eggs, juveniles and adults found at Olympic Club was higher than at Poppy Hills throughout the year. Seasonal fluctuations were observed in number of galls, eggs, adults, and juveniles within galls and soil. In general the number of galls and nematode populations (eggs, juveniles and adults) peaked from late-spring through midsummer, and then declined rapidly during late-summer (usually at the end of August) the same year. The nematode populations were correlated for most of the sampling period to the soil temperature. Our data suggest that the peak of infective juveniles that are released from the galls and search for a new host occurs during late spring and midsummer. A positive correlation was found between gall size and the nematode population within it. In light of these results, possible suggestions to improve the integrated pest management of A. pacificae are discussed.