What is Dollar Spot Disease and What Grasses are Susceptible?

One of the most problematic diseases for turf is a disease called “Dollar Spot”. It can appear on both warm and cool season grasses. Zoysia and Bermudagrass are the most susceptible of the warm season grasses and Kentucky Bluegrass, Poa annua, Creeping Bentgrass and Ryegrass are the most affected cool season grasses. It occurs more frequently on lawns with low nitrogen and micronutrients when soils are dry and humid weather starts and creates heavy morning dews. Once active, Dollar Spot will continue to damage your lawn until treated.

Dollar Spot Symptoms

Tan colored spots appear on your lawn that are 2 to 4 inches in diameter. Centers are dry, sunken and grass has a straw look to it. Mycelium might be present in the in morning when moisture is present at center of spot. Mycelium is white and can resemble the look of small spiders’ web. Mycelium will appear at first stage of disease and is my key indicator on the golf course.

Pythium though does looks similar to Dollar Spot but has a darker brown color and center of spot is slimy and wet. Pythium appears in hotter temps when night temps do not go below 70 F and day temps are in the 80sF. Dollar Spot disease becomes active above 60F air temperature and can become rampant if untreated and daily temps are between 70F – 80F with humidity. Disease will kill affected grass spots, leaving you with small patches over your lawn until adjacent grass has filled in the small voids.

Dollar Spot Treatment

People say the best cultural practice is to have more resistant turf varieties in your lawn. This is a great idea for the future when you decide to renovate but until then let’s stick to how to deal with active Dollar Spot.

Increase your nitrogen output; if you feel your lawn does look weak and sparse with thin yellow leaves; then increase your nitrogen levels and possible frequency until you start to generate dense green turf. Dollar Spot is recoverable through maintaining a healthy lawn as it can actively outgrow the pace of disease attack. Once Dollar Spot is active and conditions are favorable for the disease, I would recommend chemical control initially. First apply a contact fungicide such as chlorothalonil or Fluazinam and follow up with a systemic fungicide such as tebuconazole or propiconazole. There are many more fungicides that treat Dollar Spot, but the ones mentioned are now generic and consequently really cheap compared to agency products.