Dollar Spot Severity as Influenced by Trinexapac‐ethyl, Creeping Bentgrass Cultivar, and Nitrogen Fertility

Abstract

Dollar spot (Sclerotinia homoeocarpa F.T. Bennett) is a widely distributed and destructive pathogen of turfgrass in the United States. A 2‐yr field study was conducted at Columbus, OH, to determine the influence of a plant growth regulator, creeping bentgrass (Agrostis stolonifera L.) cultivars, and N fertility on dollar spot severity. ‘Crenshaw’ creeping bentgrass was seeded alone or in a 50:50 blend by weight with ‘Penncross’ creeping bentgrass. Plots were fertilized at 0, 24.4, or 48.8 kg N ha−1 per application. One‐half of each plot received trinexapac‐ethyl (TE) [4‐(cyclopropyl‐α‐hydroxymethylene)‐3,5‐dioxo‐cyclohexanecarboxylic acid methyl ester] at 0.8 L ha−1. The TE and fertilizer treatments were initiated in May 1995 and 1996 with four subsequent applications made at 30‐d intervals. Initially, the cultivar blend reduced the rate of dollar spot development compared with Crenshaw alone; however, neither the blend nor Crenshaw provided commercially acceptable dollar spot suppression throughout the study. Both TE and N fertilization significantly (P ≤ 0.05) reduced dollar spot severity over the 2‐yr period. Trinexapacethyl applied alone effectively suppressed dollar spot activity, but efficacy increased with increasing N rates. Dollar spot symptoms decreased and thatch thickness increased at elevated N levels. During this 2‐yr study, interactions between TE and N fertility resulted in a significant (P ≤ 0.05) reduction in dollar spot severity. Thus, on golf course fairways where dollar spot may be severe, incorporation of these two treatments into a turfgrass management program will enhance dollar spot suppression and reduce fungicide inputs.

Influence of Trinexapac Ethyl on the Efficacy of Chlorothalonil and Propiconazole for Control of Dollar Spot on Creeping Bentgrass

“…These results support other published research demonstrating that dollar spot was not suppressed and fungicide efficacy was not affected by the use of trinexapac ethyl (3,7,8). Our conclusions differ from reports suggesting that trinexapac ethyl contributes to a reduction in dollar spot severity (10,20). However, in one report (20) conclusions were based on results from a single experiment and where differences were not constant throughout the experimental period (20).…”

“…Most of the investigations on the effects of PGRs on disease development involved dollar spot. An early report described improved fungicide efficacy with use of trinexapac ethyl (Primo Maxx) against dollar spot on creeping bentgrass maintained at fairway height in Ohio (10). Several research briefs addressed combinations of trinexapac ethyl and various fungicides for dollar spot control.…”

Nitrogen Rate and Mowing Height Effects on Velvet and Creeping Bentgrasses for Low‐Input Putting Greens

“…While our study showed the moderate N rate resulted in approximately 20% more dollar spot than the low N rate, previous research has shown mixed results. Couch and Bloom (1960) also found that low N rates decreased dollar spot severity on Kentucky bluegrass (Poa pratensis L.), while other research on creeping bentgrass showed that higher N rates decrease dollar spot severity (Williams et al, 1996;Golembiewski and Danneberger, 1998). It is possible that the eff ect of N rate on disease severity depends on the interaction of species or cultivars and growing conditions.…”

The Role of Biofungicides and Organic Fertilizer in the Management of Dollar Spot in Bermudagrass

“…Dollar spot has been documented as more severe under low nitrogen fertility (12,23,25,29). Organic amendments composed of plant and animal meal and other organic sources have been reported to reduce DSSv under various levels of disease pressure.…”