Preventing/Controlling Dollar Spot Fungus on Lawns

 Have you tried to pinch pennies by managing the lawns on your properties by yourself? Has this resulted in some challenges? The LandscapExperts at Crabapple can troubleshoot and solve any lawn maintenance problems in short order. Proper lawn management including timely watering, correct fertilization and core aeration when indicated will reduce the incidence of Dollar Spot problems.

Dollar Spot is a major turfgrass disease that arrives with hot weather and is caused by a fungus that invades lawns. Since metro-Atlanta has been experiencing July-like heat during late May and June, Dollar Spot is showing up earlier this year. At first, the disease is undetectable, causing yellow hourglass –shaped lesions on the leaves of grass. Next silver dollar-sized brown spots appear on stressed lawns, which quickly coalesce to form large, irregular dead spots in the turf. When grass is wet from early morning dew, a fine, white “cobweb” appearance due to fungus strands (mycelia) may be visible. The disease can be a problem on fine-leaf fescues, bermudagrass and Zoysia, as well as on bluegrass and bentgrass. Note that turfgrass under stress is more susceptible to Dollar Spot than well maintained turf.

Crabapple LandscapExperts Steps to Control Dollar Spot; proper lawn management is the key to prevention and control.

● Core aeration to prevent the buildup of thatch a core-type aerator. (see Blog on core aeration.)  This device pulls cylindrical plugs from thatch and soil, which allows penetration of water, air and nutrients into the soil, increasing root depth of the turf. Shallow, poorly developed roots that are susceptible to drought stress result from heavy thatch layers because water, air and nutrients cannot penetrate to the underlying soil and grass roots, resulting in and resulting overwatering that promotes Dollar Spot.

● Sanitation prevents the spread of the fungus. Wheels on lawnmowers, maintenance equipment and LandscapExperts' shoes are cleaned to help eliminate transmission of the disease.

● Good nitrogen fertility. Stressed lawns are more susceptible to Dollar Spot, so Crabapple fertilizes warm season grasses during the summer growth months to promote optimum nitrogen levels. Fertilization is carefully controlled to preclude excess salt levels.

● Best horticultural practices provide attention to mowing frequency and height for best growth of lawns. Additionally, in the instance of a fungal breakout grass clippings are caught and removed. 

● Timing of Watering is important because fungus spores need about 12 hours to germinate on wet leaves.

+Very early morning watering (before sunrise) is best as it washes dew and leaf sap from the leaf surfaces and helps reduce the incidence and spread of Dollar Spot. After sunrise, a no-watering interval (about an hour) is observed to allow lawns to dry off.

+Daytime watering is sometimes practiced but loss of irrigation water may occur through evaporation at midday.

+Watering is discontinued in the late afternoon to allow the leaves of grass time to dry before nightfall, since disease may become more severe if a wet period is extended during the early evening. We do not recommend watering at night.

● Insect control and elimination of infestations of white grubs, billbug grubs and root-eating insects that cause lawn symptoms that resemble drought stress. Organic controls specific to insects are used as the first line of defense. Pesticide effectiveness in killing grubs is improved by removal of any thatch layer.

● Long periods of high humidity can promote Dollar Spot. Mother Nature is in control of this factor.

● Fungicides are used only as a last resort, because some forms of the Dollar Spot fungi are resistant to fungicides with varying degrees of tolerance to commonly used brands. Crabapple LandscapExperts specifically select and rotate fungicides targeted to individual applications. Fungicides are expensive, plus beneficial earthworms and helpful soil bacteria can be adversely affected by fungicide applications.

In conclusion, call Crabapple LandscapExperts to maintain beautiful lawns on your properties, or if you notice Dollar Spot in any areas.  

Resources: http://www.caes.uga.edu/publications/pubDetail.cfm?pk_id=7149#DollarSpot and Colorado State University Extension C. E. Swift; photos courtesy of Penn State University, UGA Urban Agriculture