Knowledgebase
Help with my Dollar Spot #878555
Asked July 24, 2024, 11:29 AM EDT
Genesee County Michigan
Expert Response
Hello Del,
It is difficult to positively confirm a fungal disease from a picture alone. I see lesions on the blades, but I cannot positively confirm dollar spot. It could also be a different fungal infection such as a patch disease. The key difference is that in the morning dew, you can see fungal webbing on the blades of the grass if it is dollar spot.
If it is dollar spot, fungicides can be used as a “preventative” or a “curative” application. In order to be preventative, you would have needed to apply the fungicide when the fungal spores were first infecting the grass – before the brown spots appeared. This year that was probably late in May to mid-June. When you see the signs of dollar spot, the fungal disease is already well established. Curative applications need to be much stronger and it is very difficult to eradicate all the spores.
Dollar spot affects grass when it is struggling to grow. You can try giving your lawn frequent light doses of nitrogen fertilizer, rather than heavy doses farther apart. Also, frequent lighter watering in dry weather is better than infrequent “drenching” applications. Right now, a dose of nitrogen may help the grass plants to outgrow the disease. You can apply a 50% strength nitrogen application. This usually equates to about ½ lb of nitrogen per 1000 sq ft.
Here are a couple of good references:
https://www.canr.msu.edu/ipm/diseases/dollar-spot
https://content.ces.ncsu.edu/dollar-spot-in-turf
Dollar spot is a large problem for golf courses. Not many references specifically address treatment in a residential lawn. The following reference does:
https://extension.psu.edu/turfgrass-diseases-dollar-spot-causal-fungus-clarireedia-jacksonii
If it is patch disease, the cultural control is almost opposite of dollar spot treatment. Patch disease does well in highly maintained, well watered, well fertilized lawns. Here is a good article on Patch Disease: https://extension.umd.edu/resource/summer-patch-lawns/
The only way to confirm exactly what disease is affecting your lawn is to take a sod sample and submit it to the MSU Diagnostic Laboratory for testing. Here is a list of services and charges: https://www.canr.msu.edu/pestid/
This site helps with taking a good sample: https://www.canr.msu.edu/pestid/submit-samples/
Hope this helps.