What is this on my holly tree leaves? It seems to be coming from the ground...

Asked May 28, 2019, 8:29 AM EDT

What is this on my holly tree leaves? It seems to be coming from the ground below. A pear tree above it has black spot disease. What is putting holes in my hosta plants? By the end of season they are totally gone.

Anne Arundel County Maryland scale insects slugs holly hosta tree

1 Response

The black substance you see on the leaves is called sooty mold. This is caused by a type of scale insect. Scale insects suck the plant sap and secrete a sugary substance called honeydew. The mold grows on the honeydew.

You can look along the stem or on the leaf undersides for the scale insects. It is possible you may be referring to cottony camellia scale. See our website below. You can manage this insect with the application of horticultural oil. Follow label directions and do not spray in high temperatures. https://extension.umd.edu/hgic/cottony-camellia-scale-shrubs

If this is not what you are noticing you can send us more photos of the insect.
You can also send photos of symptoms on the pear leaves.

The holes in the hosta leaves looks like slug damage. Here is our website and ways to manage slugs. https://extension.umd.edu/hgic/topics/slugs-and-snails-flowers

Marian