Plant Health Characteristics of Creeping Bentgrass Affected by Strobilurin Fungicide Applications and Turfgrass Diseases

Abstract

Previous research has indicated that strobilurin fungicide applications may mitigate the effects of summer heat stress on creeping bentgrass (Agrostis stolonifera L.). Two multi‐year experiments were conducted in 2011 and 2012 to evaluate plant health characteristics following strobilurin fungicide applications to creeping bentgrass putting greens. In Exp. 1, pyraclostrobin, azoxystrobin, fluoxastrobin, or trifloxystrobin were integrated within a conventional summer fungicide program. In Exp. 2, repeated applications of strobilurin fungicides were evaluated in absence of visible foliar disease. To limit foliar disease, overspray applications of chlorothalonil (2,4,5,6‐tetrachloroisophthalonitrile) and iprodione [3‐(3,5‐dichlorophenyl)‐N‐isopropyl‐2,4‐dioxoimidazolidine‐1‐carboxamide] were applied over the experimental units. The plant health characteristics evaluated were visual quality, spectral reflectance, percent green cover, and root morphology. Disease incidence and severity was also quantified visually. In Exp. 1, the nontreated control was similar to strobilurin fungicide programs in all parameters in 2011. In 2012, strobilurin fungicide programs exhibited improved normalized difference vegetation index (NDVI), ratio vegetation index (RVI), turfgrass quality, and percent green cover compared to the nontreated control. Disease severity also increased in 2012 compared to 2011. In Exp. 2, repeated applications of strobilurin fungicides did not affect measured parameters compared to the nontreated control when foliar diseases were managed with fungicides chlorothalonil and iprodione. In these experiments, differences in NDVI, RVI, turfgrass quality, and percent green cover often coincided with differences in disease severity in our evaluations. Under the conditions of these studies, applications of strobilurin fungicides have limited effects on NDVI, RVI, turfgrass quality, and percent green cover in the absence of visible disease.

Mechanisms of Environmental Stress Tolerance in Turfgrass

“…The application of chemical agents is a common method to avoid biotic-stress-induced damage in turfgrass. For instance, dollar spot disease in turfgrass is caused by the fungus Clarireedia homoeocarpa, and it could be suppressed by fungicide in creeping bentgrass [199][200][201][202]. Captan and Chlorothalonil are efficient fungicides against Curvularia trifolii, which causes foliar yellowing of Paspalum vaginatum [5,194].…”

Effects of fungicides on creeping bentgrass health and rooting characteristics under abiotic stress

“…Our results are in agreement with other studies conducted where drought is not as prominent as in California. Benelli et al (2016) did not observe any advantageous impact of QoI fungicides on either CBG quality and rooting while grown in the field conditions in the absence of visible disease in Knoxville, TN. In addition, Thompson et al (2017) also did not observe any positive impact of azoxystrobin or pyraclostrobin on roughstalk bluegrass (Poa trivialis L.) rooting in field conditions.…”

“…However, the authors reported lack of improvement in CBG quality in response to any of the employed QoI fungicide applications when compared to nontreated plants. In addition, Benelli et al (2016) did not observe improved plant health characteristics when strobilurin fungicides were applied to CBG with foliar disease managed by overspray with other classes of fungicides. Therefore, claims of QoI field performance in turfgrass settings still lack unequivocal proofs.…”

Influence of post‐application irrigation and mowing timing on fungicide fate on a United States Golf Association golf course putting green

“…A 1.6-unit increase in turfgrass quality and a 32% increase in root length were observed in plants inoculated with Magnaporthiopsis poae (Summer Patch) receiving post-application irrigation compared with inoculated pots receiving fungicide alone (nonirrigated) (Hutchins et al, 2019). Similarly, Wong and Corza (2005), Benelli et al (2016), andButler (2004) found that applying fungicides in higher carrier volumes increased efficacy on summer patch, large patch (Rhizoctonia solani), spring dead spot (Ophiosphaerella spp. ), and leaf spot (Drechslera poae).…”