Roses are a beloved staple in many gardens, known for their stunning blooms and romantic symbolism. However, growing healthy roses can be challenging—especially when common plant diseases take hold. Among the most frequent reasons gardeners struggle with rose cultivation is poor disease control, with black spot and powdery mildew topping the list of threats.
Black Spot: The Most Serious Rose Disease in North Carolina
Black spot is a particularly aggressive fungal disease and the leading cause of rose decline in North Carolina. The disease first appears as circular black spots with fringed edges on the upper surface of leaves. As it progresses, leaves turn yellow and fall prematurely, leading to defoliation. Without intervention, the disease weakens plants, reducing flower production and increasing susceptibility to other pests, diseases, and winter damage.
The disease thrives in wet conditions and spreads quickly, with new spots developing within 5 to 10 days. Consistent and early intervention is key. Experts recommend beginning a spray program in early spring as new growth appears and continuing every 7 to 10 days—or after heavy rain—throughout the growing season.
A thorough application is essential: both sides of each leaf must be uniformly covered. Infected leaves should be removed immediately during the growing season. At the end of the season, rake and discard fallen leaves and prune hybrid tea roses to about 18 inches in fall, then again to 10 to 18 inches in early spring—always discarding the clippings.
Powdery Mildew: Another Common Culprit
Powdery mildew, another fungal foe, manifests as a white, powdery coating on young leaves, stems, and flower buds. It causes leaf distortion, though not as much leaf drop as black spot. This disease is more prevalent in shaded areas and during cool, damp conditions. Like black spot, it spreads rapidly and should be controlled through regular removal of affected plant parts and a consistent fungicide spray regimen.
Fungicide Options for Effective Control
Effective fungicides include products with active ingredients such as chlorothalonil, copper, triforine, propiconazole, or myclobutanil. These are widely available at garden centers and home improvement stores. Rotate fungicides for best results and apply every 7 to 10 days, ensuring all plant surfaces are covered. Always read and follow label instructions carefully.
Note: Mention of specific fungicide names does not imply endorsement by North Carolina Cooperative Extension and should not be seen as a preference over other, similar products.
Need Gardening Help? Wayne County Extension is Here for You
If you have questions about growing roses or other garden challenges, the Wayne County Extension Master Gardener Volunteer Plant Clinic is open from 10 a.m. to 1 p.m. on Mondays, Wednesdays, and Fridays (March through June). Stop by The Maxwell Center (3114 B Wayne Memorial Drive, Goldsboro), call 919-731-1433, or email Master.Gardener@waynegov.com.
To stay up to date with seasonal gardening tips, sign up for the Wayne County Extension Gardening e-mail list at wayne.ces.ncsu.edu/email-me.
You can also follow them on Facebook (@waynecooperativeextension) and Instagram (@waynecountyextension).
Explore even more plant ideas through the NC Extension Gardener Plant Toolbox: https://plants.ces.ncsu.edu
