virus on Daisy leaves?

Asked June 20, 2019, 4:31 PM EDT

Here are a couple of photos of the lower leaves of my daisies. They have been getting this yellowing w/ brown spots for several years now. It seems to start on the lower leaves and keep affecting more and more as I remove them. :( Can you offer any organic advice? Thank you.

Wayne County Michigan

4 Responses

Most leaf spot diseases require cool conditions, wet foliage, high humidity, and little air movement. These conditions occur regularly in mature landscapes and gardens where the plants have grown together and air movement is somewhat inhibited. Overwatering or heavy clay soil can also cause fungal leaf spots and yellowing.

The occurrence of leaf spots can be minimized by keeping the foliage as dry as possible and providing irrigation early in the day to allow the foliage to dry quickly and not stay wet during the night. Plants in the landscape should not be overcrowded and have an adequate amount of space between each plant.

Most products effective at controlling leaf spots are best used on a preventative basis (prior to visible leaf spots). To prevent leaf spot diseases try preventive applications of a natural fungicide containing neem oil. To eliminate leaf spots, all of these products need to be applied before the leaf spots are present. These fungicides can stop fungal leaf spots from spreading once they are visible, but cannot make any existing leaf spots disappear.

Some common diseases that affect shasta daisies (Leucanthemum x superbum) are alternaria leaf spot, septoria leaf spot, botrytis, powdery mildew, The treatment for any of these is the same.

Below are some cultural tips to help reduce fungal disease:

  • Remove and destroy diseased leaves and plants at the end of the growing season.
  • Keep plant tops as dry as possible by applying water to soil, not sprinkling over plants.
  • Rotate planting beds.
It is difficult to properly identify the pathogen causing leaf spots. If you experience persistent problems (year after year) with the same type of leaf spot, it may be beneficial to contact your local extension agent and/or submit samples to a diagnostic clinic for diagnosis ( Once the pathogen has been identified, you can determine if control strategies are necessary.

Thank you for your response. I almost never water my daisies, but they are overcrowded. Your advice says to remove and destroy diseased plants and rotate beds. Does this mean the only solution is to rip out 25ft of daisies along my fence that have grown there for 14 years? Or is it worthwhile to thin them and then treat them next spring with a fungicide? If so, how far apart should the daisies that I leave be?

I did not mean to imply that you should tear out your entire daisy bed! A proper procedure would be to first remove and destroy any plants that are seriously infected with the fungal disease, if any. Then remove a few plants (maybe every third one depending on how close together they are) to improve air circulation around each plant. Then apply a fungicide to the plants you are going to save. This will not remove the leaves that are already infected, but it will protect the leaves that are still healthy. Always carefully read and follow instructions on the fungicide bottle.

Since most fungal diseases overwinter in the leaf litter, you may wish to cut back and destroy the foliage when it has finished for the season and rake the leaf litter from around the plants and destroy it too. This should help minimize a re-infection next spring.

Thank you very much! :)