Summary
In Georgia there are 800,000 acres of home lawns and on average homeowners spend $400.00 per acre annually to maintain their lawn. Tall fescue (Festuca arundinacea) is one of the most popular grasses in the mountains and upper Piedmont areas of Georgia. Tall fescue is highly susceptible to Rhizoctonia solani the causal organism of the disease termed “brown patch”. There are no tall fescue types with reported resistance to R. solani; therefore control depends on the use of fungicides. A series of field experiments were performed to evaluate the efficacy of fungicides against R. solani on tall fescue. New liquid formulations of azoxystrobin as well as new granular formulations of azoxystrobin, tebuconazole and trifloxystrobin + bayleton specifically developed for the lawn care market had statistically significant R. solani (brown patch) suppressing effect. Results from our investigations have helped in the labeling of these products for commercialization.
Situation
Popularity of home lawns has grown tremendously in the US. Generally home lawns represent the largest segment of the turfgrass industry. In Georgia there are 800,000 acres of home lawns and on average homeowners spend $400.00 per acre annually to maintain their lawn. Tall fescue (Festuca arundinacea) is one of the most popular grasses in the mountains and upper Piedmont areas of Georgia, this area extends as far south as Atlanta. Tall fescue adapts to a wide range of soil types but grows best on fertile, well drained soil with a soil pH of 5.5 to 6.5. In Georgia, the growth and competitive ability of tall fescue declines during times of high heat and humidity. Tall fescue is highly susceptible to Rhizoctonia solani the causal organism of the disease termed “brown patch”. The pathogen incites foliar blight that results in necrotic leaves which form patches of up to 1m in diameter in turfgrass swards. Symptoms are more severe when night time temperatures are above 16C which coincides with 10 h of leaf wetness. There are no tall fescue types with reported resistance to R. solani; therefore control depends on the use of fungicides.
Response
A series of field experiments were performed to evaluate the efficacy of fungicides against R. solani on tall fescue. Fungicide trials were conducted on a 6-year-old sward of tall fescue grown on a clay loam soil (pH 5.8) at the Georgia Experiment Station, Griffin, GA. The tall fescue variety used in these trials was Kentucky 31. An isolate of R. solani from tall fescue was used for inoculation purposes. Fertilizer treatments consisted of 1.0 lb nitrogen per 1000 sq ft prior to the onset of the experiments and as needed according to previously scheduled rotation within UGA turf maintenance department guidelines. The turfgrass was maintained at a height of 2.5 in. by mowing once a week. Turfgrass cultural practices were similar to those prescribed for maintenance of tall fescue lawns in Georgia. Treatments were arranged as plots (1.5m x 1.5m) in a randomized complete block design with four replications. Granular fungicides were weighed and at the time of inoculation mixed with sterilized sand which was contained in a lid-perforated canister. Fungicide was distributed evenly throughout the experimental plot. Liquid treatments were mixed with water and sprayed with a hand held CO2-pressured boom sprayer at 30 psi. Experimental plots received 0.1 in. of irrigation water daily 3 times a day (11:00 AM; 3:00 PM and 7:00 PM) to ensure nightly foliar wetness for disease infection. Normal irrigation was received at 3:00 AM. Visual estimates of disease severity were made using the Horsfall-Barratt rating scale. Values were subjected to analysis of variance and means were statistically separated using the LDS analysis procedure at a probability value of P= 0.05.
Impact
New liquid formulations of azoxystrobin as well as new granular formulations of azoxystrobin, tebuconazole and trifloxystrobin + bayleton specifically developed for the lawn care market had statistically significant R. solani (brown patch) suppressing effect. Results from our investigations have helped in the labeling of these products for commercialization. Additionally it was found that rates of 1.5 oz per 1000 sq ft of liquid formulations of trifloxystrobin + bayleton provided significant disease control for longer periods of time (over 28 days) when compared with previous established rates (1.0 oz and 1.2 oz per 1000 sq ft). Results indicated that rotations of flutolanil followed by trifloxystrobin + bayleton were also effective in controlling the disease. It was also found that pyraclostrobin at a concentration of 0.9 oz per 1000 sq ft can provide statistically significant disease control for 35 days even environmental conditions were highly favorable for disease development. Results obtained in these investigations provide turfgrass managers with new disease management tools, improved disease control, and better turf quality.
State Issue
Agricultural Profitability and Sustainability
Details
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Year:
2007
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Geographic Scope:
Multi-State/Regional
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County:
Spalding
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Program Areas:
- Agriculture & Natural Resources
