What To Do About Black Bugs On Sunflowers

What are the black bugs on your sunflowers, and should you be concerned? If you’ve noticed clusters of tiny black insects covering sunflower leaves, you’re not alone. Before reaching for a spray bottle, it’s important to identify the culprit and understand whether treatment is actually necessary.

In many gardens, these black bugs are chrysanthemum lace bugs (Corythucha marmorata). You may see them as tiny dark nymphs clustered on the undersides of leaves, along with larger adults feeding on both sides of the foliage. In this guide, you’ll learn how to identify chrysanthemum lace bugs, recognize the damage they cause, and decide when intervention is needed. You’ll also discover organic ways to manage them while protecting the beneficial insects that help keep your garden healthy and productive.

What Are Chrysanthemum Lace Bugs?

Chrysanthemum lace bugs are active during the warmer months of spring through summer and often feed on herbaceous plants and perennials in the Aster family, such as sunflowers, asters, and black-eyed Susans.

Adults: ⅛ to ⅓ inch long. Light brown or grey bodies. Flat wings are slightly longer than the body. Lacy in appearance. Often found on the top of leaves as well as the undersides.

Nymphs: Smaller and darker than adults. Wingless, brown, and shiny. They suck sap from the leaf and are often found clustered on the underside of leaves. Nymph exoskeletons remain on plants after molting. 

Eggs: Tiny and dark brown. Females insert the eggs into the more prominent veins of leaves and cover them with a varnish-like excretion (frass), which secures the eggs to the leaves. If you are finding eggs near a pest colony on your sunflowers, check what they are before you remove them. This guide to identifying beneficial insect eggs in the garden will help you tell the difference.

What Damage Do Chrysanthemum Lace Bugs Cause?

The piercing mouth parts suck sap from the leaves and create a mottled appearance on the top of the leaves. When there are many bugs, the leaves get discolored and often fall off prematurely. 

Larger plants may tolerate more damage than smaller plants. Monitor new growth and young leaves, and follow the treatment plan (listed below) as needed.

Which Plants Are Commonly Affected by Chrysanthemum Lace Bugs?

The most affected plants are sunflowers and other Aster family members, including mums, black-eyed Susans, and asters. 

What Should I Do When I See Black Bugs on My Sunflowers? 

If lace bugs are not present in enough numbers to cause damage, do nothing.

Next, consider removing heavily-infected leaves and spraying the remaining leaves with a strong stream of water. This treatment is usually enough to keep numbers under control.

If the infestation is severe and causing damage, and you want to treat it, apply horticultural oil to both sides of the leaves to reduce the numbers.

Do Chrysanthemum Lace Bugs Have Natural Predators?

Yes!! Lacewing larvae, hoverfly larvae, and ladybugs are natural predators of chrysanthemum lace bugs. Follow organic gardening principles, and there is a good chance the good guys will help limit the number of chrysanthemum lace bugs on your sunflowers.

And if the insects aren’t black but tiny and white and they fly up when you disturb the plant, those are usually whiteflies. This guide shows you how I get rid of whiteflies. If the bugs you’re seeing are actually aphids clustered on new growth, this guide will help you decide whether to ignore them or spray them off.

Are you looking for more information about growing sunflowers?

Pests aside, these tall plants do real work for me. I grow branching sunflowers to shade my vegetable beds through the hottest part of the year.

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Source used for information: https://content.ces.ncsu.edu/chrysanthemum-lace-bug.