Brown bugs on lilac bush - Ask Extension
I have a very old lilac bush with leaves that have begun to brown on the edges as well as having brown spots throughout. When I was looking closely ...
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Brown bugs on lilac bush #800147
Asked July 08, 2022, 6:35 PM EDT
I have a very old lilac bush with leaves that have begun to brown on the edges as well as having brown spots throughout. When I was looking closely at some of the leaves I saw some tiny brown and black bugs and on some of the leaves there was a white, web-like material. I have attached pictures of the leaves and bugs. Unfortunately the leaf I pulled off to investigate didn't have the web.
Frederick County Maryland
Expert Response
The photos didn't seem to attach to my original question. Here they are.
The brown leaf spotting is probably due to a bacterial pathogen; lilac is known to contract several infections when weather conditions are conducive. There is no treatment that will reverse symptoms, and few fungicides have any effect on bacterial diseases. Even when effective, fungicides must be applied prior to the development in symptoms, earlier in spring, and likely re-applied a few times (according to product label directions). Fortunately, late-season leaf damage on lilacs doesn't tend to cause them much harm to the shrubs overall. You can learn more about common lilac ailments and their management on our Lilacs: Identify and Manage Problems page.
Can you share photos of the webbing and dark insects? (If these insects are in the attached photos, we can't see them well.) Lilac has relatively few insect pests, and while borers tend to target older wood (in thick stems several years old), the adults themselves are rarely seen and would be fairly large compared to common garden pests like aphids or beetles.
Miri
Can you share photos of the webbing and dark insects? (If these insects are in the attached photos, we can't see them well.) Lilac has relatively few insect pests, and while borers tend to target older wood (in thick stems several years old), the adults themselves are rarely seen and would be fairly large compared to common garden pests like aphids or beetles.
Miri
The bugs are very tiny and look like they have wings. They were in the pictures that I sent but I will try again with these. The first two are the pictures of the webbing with no bugs and the last one has two brown bugs on the large brown spot. I hope they are more clear but are very hard to photograph.
Thank you,
Christina
Hello Christina,
These are leafhoppers and/or planthoppers. (They are closely related and sometimes hard to tell apart. Between the two groups, several hundred species occur in Maryland.) The juveniles produce the white, cottony wax that covers their bodies, with some residues getting left behind as they wander and jump about. Adults vary in color depending on the species, but can be shades of brown, powdery gray-green, lime green, or gray; a few are more colorfully marked with brighter colors. The wax may conceal them from predators and/or minimize desiccation in hot, dry weather.
They rarely pose a health threat to plants and no management is needed. (They pose no known risk to lilac.) If you prefer, you can try blasting the lilac with a strong jet of water from a garden hose to dislodge most of them; the adults might fly back onto the plant, but the juveniles will have a harder time since they can't fly, and may disperse instead.
Miri
These are leafhoppers and/or planthoppers. (They are closely related and sometimes hard to tell apart. Between the two groups, several hundred species occur in Maryland.) The juveniles produce the white, cottony wax that covers their bodies, with some residues getting left behind as they wander and jump about. Adults vary in color depending on the species, but can be shades of brown, powdery gray-green, lime green, or gray; a few are more colorfully marked with brighter colors. The wax may conceal them from predators and/or minimize desiccation in hot, dry weather.
They rarely pose a health threat to plants and no management is needed. (They pose no known risk to lilac.) If you prefer, you can try blasting the lilac with a strong jet of water from a garden hose to dislodge most of them; the adults might fly back onto the plant, but the juveniles will have a harder time since they can't fly, and may disperse instead.
Miri
