Residual Stripe Smut Control in Kentucky Bluegrass with Reduced Fungicide Levels

Abstract

Abstract Stripe smut [Ustilago striiformis (West.) Niessl.] is a destructive disease of ‘Merion’ and several other cultivars of Kentucky bluegrass [Poa pratensis L.). Fungicides (all in kg·ha-1) were foliar-applied to a diseased stand of ‘Merion’ Kentucky bluegrass in spring while disease symptoms were evident. In the initial study, sequentially applied (14-day interval) triadimefon (3.0 + 3.0) and terbuconazole (1.6 + 1.6) provided excellent control and commercially acceptable turfgrass quality 2 years after fungicide application. Propiconazole (1.7 + 1.7) provided good disease control; however, benomyl (6.1 + 6.1), fenarimol (3.0 + 3.0), iprodione (6.1 + 6.1), and prochloraz (7.6 + 7.6) provided poor disease control when plots were rated 2 years following application. In the second study, a single application of terbuconazole (1.6) and diniconazole (1.5 or 3.0) provided excellent stripe smut control, and turf exhibited commercially acceptable quality 2 years following fungicide application. Triadimefon-(1.5 or 3.0), terbuconazole- (0.8), and propiconazole- (1.7) treated turf exhibited reduced disease injury after 2 years; however, turf quality was not as good as that provided by the other fungicide treatments. Observations and data collected over 3 years do not support the view that U. striiformis-infected plants die during summer stress periods, thereby controlling the disease by reducing large populations of perennially infected plants. Chemical names used: methyl[1-[(butylamino)carbonyl]-1H-benzimidazol-2-yl]carbamate (benomyl); α-(2-chlorophenyl)-α-(-4-chlorophenyl)-5-pyrimidinemethanol (fenarimol); 1-isopropylcarbamoyl-3-(3,5-dichlorophenyl) hydantoin (iprodione); 1-(2,4-dichlorophenyl)-4,4-dimethyl-2-(l,2,4,-triazol-1-yl)-1-peneten-3-ol (diniconazole is proposed); N-propyl-N-[2-(2,4-6-trichlorophenoxy)ehyl]-1H-imidazole-1-carboxamide (prochloraz); 1-(2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl methyl)-1H,2,4-triazole (propiconazole); a-[2-(4-chlorophenyl)ethyl]-a-(1,1-dimethylethyl)-H-l,2,4-triazole-1-ethanol (terbuconazole is proposed); 1-(4-chlorophenoxy)-3,3-dimethyl-1-(lH-l,2,4-triazol-1-yl)-2-butanone (triadimefon).