Spots on Leaves

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, Actinovate, Serenade, Green Cure 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.

Some plants are more prone to leaf spot than others, especially if the leaves are frequently hit with irrigation. Cherry laurel is one of those plants.

Some plants are more prone to leaf spot than others, especially if the leaves are frequently hit with irrigation. Cherry laurel is one of those plants.

Sometimes people mistake fungal problems for insect damage. Once the tissue dies it falls away, as you can see in this photo, leading many to think that the plant is being eaten. In these cases an insecticide won't work because it's a fungal problem, not a bug.

Sometimes people mistake fungal problems for insect damage. Once the tissue dies it falls away, as you can see in this photo, leading many to think that the plant is being eaten. In these cases an insecticide won’t work because it’s a fungal problem, not a bug.

Some perennials are prone to fungal problems as you see here. Although there is nothing you can do to get rid of the fungi once the plant looks like this, if you start spraying with one of the fungicides mentioned early next season you can prevent the problem from getting this bad in future years.

Some perennials are prone to fungal problems as you see here. Although there is nothing you can do to get rid of the fungi once the plant looks like this, if you start spraying with one of the fungicides mentioned early next season you can prevent the problem from getting this bad in future years.

Once basil gets a problem the best thing to do is to remove all the worst leaves and start spraying with an organic fungicide to slow the infection down.

Once basil gets a problem the best thing to do is to remove all the worst leaves and start spraying with an organic fungicide to slow the infection down.

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