Factors Associated with Populations of Plant-Parasitic Nematodes in Bentgrass Putting Greens in Oklahoma.

Numerous genera of plant-parasitic nematodes are frequently present at high populations in golf course putting greens. The objectives of this research were to identify and quantify plant-parasitic nematodes from Oklahoma bentgrass putting greens and to characterize specific soil physical and chemical features and management factors that may account for differences in or associated with the observed nematode populations. In the fall of 2000, nematodes were identified from 99 individual bentgrass putting greens sampled from 46 different locations in Oklahoma. In addition to green age and bentgrass cultivar; soil pH, nitrate-nitrogen (NO₃-N), plant-available phosphorus and potassium, organic matter (OM), bulk density, and particle size distribution were determined for each green. Expenditures on management activities, including fertilizer, herbicide, fungicide, and insecticide, were determined for 20 of the sampled courses and compared with nematode populations. Nematodes from seven genera were found in Oklahoma greens, with Criconemella spp. being the most common. Paratrichodorus spp., Tylenchorhynchus spp., and Helicotylenchus spp. also were common. The logarithmic populations of all nematodes combined increased with greater green age (r = 0.37). A negative relationship was observed between soil bulk density and all nematodes combined (r = -0.29). Soil NO₃-N, plant-available K, and OM increased with combined logarithmic populations of all plant parasitic nematodes (r = 0.23, 0.28, and 0.37, respectively). A four-factor model accounted for 75% of the total variation in the data and permitted groupings of all variables into four uncorrelated factors. Total logarithmic nematode populations increased with fungicide and herbicide expenditures (r = 0.31). This study suggests that populations of plant-parasitic nematodes may be influenced by the putting green abiotic soil environment and possibly indirectly by management practices on putting greens.