Distribution of plant-parasitic nematode species on golf greens in Missouri and Indiana

Several plant-parasitic nematode (PPN) species cause decline in the health of creeping bentgrass putting greens. PPNs target and parasitize the root systems of turfgrass which may exacerbate the impact of other biotic and abiotic stress. Turfgrass managers often apply nematicides preventatively or curatively to control PPN populations. However, the inherent chemistries of the nematicides may inhibit their ability to permeate through the thatch layer and soil, resulting in an ineffective application. This research aimed to evaluate the depth of PPN populations through the growing season to maximize the effectiveness of nematicide applications, with a primary focus on lance (Hoplolaimus spp.) and root-knot nematodes (Meloidogyne spp.). To determine the depth of genera across time, soil samples were taken with a 1.9 cm diameter soil probe to a depth of 25 cm during the months of April, June, August, and October at 7 sites across Missouri, three in eastern Kansas and ten sites in Indiana in 2021 and 2022, respectively. Significant interactions occurred between sampling depth and month in both Missouri and Indiana for some PPN genera. Additionally, individual lance and root-knot nematode species obtained from sampling were characterized with molecular methods and in the case with one lance nematode from Indiana, with scanning-electron microscopy. Results suggest an over-representation of H. galeatus in diagnostic literature, and a diverse collection of Meloidogyne spp. present in Indiana on golf course putting greens.