Research Topic: Dollar Spot Control with Fungicides and Ultraplex® (2008). Turfgrass Disease Solutions. McDonald, S., Primary Investigator. Brookside CC, Pottstown, PA

Dollar spot (Sclerotinia homeocarpa) remains a common and persistent disease problem on most warm- and cool-season turfgrass species. Adequate chemical control of dollar spot can be achieved with variety of fungicide chemistries including nitrils (chlorothalonil), benzimidazoles (thiophanate methyl), triazoles (propiconazole), and carboximides (boscalid). Resistant isolates of dollar spot have been reported for several fungicide groups including dicarboximides, benzimidazoles, and sterol biosynthesis inhibitors; therefore read labels carefully, tank mix or rotate fungicides with different modes of action, and implement sound cultural practices that increase plant vigor and limit disease development. These cultural practices include deep and infrequent watering while maintaining soil water near field capacity, remove dew mechanically, promote good air circulation, maintain adequate to high nitrogen (N) fertility when dollar spot is active. The objective of this study was to evaluate the effectiveness of a foliar fertilizer (Ultraplex®) (5-0-3) and containing a non-inonic surfactant to increase the efficacy of propiconazole (Banner MAXX) applied at 0.5 fl. oz./M and on a 28 day interval to a creeping bentgrass (Agrostis stoloniferous) fairway. No dollar spot was observed in May, mild pressure occurred in June and severe pressure was evident by early July. All plots containing Banner MAXX had significantly less disease pressure than the control. On both July 11 and July 18, the addition of Ultraplex to Banner MAXX significantly reduced dollar spot pressure (Figure 1). In addition and because Ultraplex has nutrient value, turf treated with a combination of Ultraplex and Banner MAXX displayed significantly better overall quality than turf treated with Banner MAXX alone (Figure 2). Turf treated with Banner MAXX and 6 fl. oz./M Ultraplex had significantly less dollar spot than turf treated with Banner MAXX and 3 fl. oz./M of Ultraplex, indicating an Ultraplex rate effect (data not shown). These results suggest that utilizing Ultraplex (6 fl. oz./M) in combination with 0.5 fl. oz./M Banner Maxx will significantly improve dollar spot control compared to Banner MAXX alone when applied on a 28 day spray interval. It is hypothesized that the nitrogen (5% N) and non-ionic surfactant in Ultraplex are contributing to the results documented in this trial. Utilize Ultraplex as one component to dollar spot management on creeping bentgrass maintained as a golf course fairway. 

Figure 1. Dollar spot (Sclerotinia homeocarpa) infection centers per plot on creeping bentgrass as influence by Banner MAXX applied with and without Ultraplex. 

*Means followed by a different letter are statistically different (P=0.05) 

Figure 2. Overall quality of creeping bentgrass as influence by Banner MAXX applied with and without Ultraplex. 

*Means followed by a different letter are statistically different (P=0.05)