Combined effects of lance nematode populations and use of plant growth regulators on creeping bentgrass putting greens

Plant growth regulators (PGRs) are used to optimize turfgrass growth, reduce management inputs, and potentially mitigate diseases. However, golf course superintendents have reported anecdotal evidence linking increased PGR‐induced phytotoxicity with high populations of lance nematodes ( Hoplolaimus galeatus ). The purpose of this study was to investigate the relationship between PGR usage and lance nematode populations on creeping bentgrass putting green health during summers in the Mid‐Atlantic United States. A 5 × 2 factorial design with five levels of PGR and the presence or absence of fluopyram was studied across five locations and 6 site‐years in the field. Four PGR treatments consisted of trinexapac‐ethyl, prohexadione calcium, flurprimidol, and paclobutrazol, along with a non‐treated control. Fluopyram was applied four times at 28‐day intervals to control other plant‐parasitic nematodes, with little efficacy against H . galeatus , and was compared with a non‐treated control. The combined effects of PGR applications and elevated lance nematode populations did not contribute to a decline in creeping bentgrass putting green quality on 57 of 63 assessment dates. Prohexadione calcium caused damage at five assessment dates within a location over 2 site‐years. An interaction between prohexadione calcium and lance nematode damage was identified in this study, but the overarching finding is that damage by a combination of PGR use and lance nematode presence is limited.