My Hydrangeas Have Black Spot Fungus. I Have Sprayed And Sprayed Copper Fungicide But Can’t Seem To Control It.

Question

They used to be beautiful, this started two years ago. I start spraying as soon as leaves appear in the spring but can’t seem to control it. What do I do? Thoughts

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Answer 1

Howdy neighbor! You are just down the road from me!

This can be chalked up to a few things. The first thing to consider is location. This should be in a fairly shaded location out of full sun. Keeping these in full sun can make them much more susceptible to damage and infection.

The next thing to consider is watering habits. At most, the soil should remain, only, slightly moist. The soil should never stay wet for long, and never allowed to dry out past, about, the 4 inch mark. The best thing will be to let it dry, thoroughly, down to about 2 inches. This is where most bad microbes will live, and they cannot survive dry soils.

Next, black spot is a particularly aggressive fungus, though not usually detrimental to the plant's health. It can stave off flowering, though. It is most prevalent in wet soils.

What you are doing now is part of a good care routine, but there is more to it.

Make sure that all fallen leaves are removed and completely disposed of or destroyed, since that is how the disease continues its lifecycle.

Keep treating, once a week or so, with copper fungicides. It will be very helpful to fight the disease with other fungi, as well. Biofungicides can be very helpful, here.

Here are some articles that will help:

https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/spots-on-hydrangea-leaves.htm

https://www.gardeningknowhow.com/special/organic/biofungicide-information.htm