Spots on Leaves

This is the time of year when many start to notice spots on foliage. This might be on your peppers, tomatoes, hydrangeas, perennials or herbs. Shrubs, trees, and flowering plants can all show signs of leaf spot and some plants are more susceptible to it than others.

Most leaf spots are fungal. Some of them just look bad (a cosmetic problem) while others will cause the leaves to yellow and prematurely fall from the plant. Leaf spot is more likely to form when nights are cool so in a summer with “good sleeping weather” we are more likely to see spotted foliage. Leaf spot is also more likely to form when foliage is being frequently splashed with water.

When you notice spots on foliage the first thing to ask yourself is if the plant is getting hit with an irrigation system, sprinkler or by hand watering. Adjust your sprinklers or watering practices so that the plants are getting deeply soaked less often. Whenever possible, water so that the leaves are not getting wet.

Secondly, if feasible remove the worst of the damage so that you can monitor if the damage is still continuing. To protect undamaged foliage spray with one of the organic fungicides such as sulfur, Revitalize, Neem Max, or copper.  If the problem is bacterial not fungal, this won’t solve the problem but since most problems are fungal this is a reasonable response.

For more information print out our handout about leaf spot.