What To Do About Black Bugs On Sunflowers

What are the black bugs on sunflowers, and what should you do about them? Before reaching for toxic sprays, find out the best ways to treat them organically. 

It’s sunflower season, and you may have noticed black dots along the undersides of sunflower leaves. Upon closer inspection, you may also see larger bugs on the tops and undersides of the leaves.

You’re probably noticing chrysanthemum lace bugs (C. marmorata) in different stages of life on your sunflower plant.

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. 

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.

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