Several counties are reporting problems with their roses. One of
those problems is rose rosette virus. The classic symptoms that
may appear include:
• Rapid elongation of a new shoot
• “Witches’ broom” (clustering of small branches)
• Branches develop excessive thorns
• Small, deformed, reddish-purple leaves
• Certain varieties may develop streaks or blotches of
reddish-purple on stems and petioles
• Plant death
Infected plants, including the roots, should be removed and
destroyed. Garden tools that come in contact with the plant need to be sterilized to
avoid spreading the virus.
Rose blackspot has also been reported. Blackspot is a fungal disease that can cause
these symptoms:
• Dark, circular lesions with feathery edges on top surface of leaves (usually lower
leaves are infected first)
• Raised, purple spots on young canes
• Yellowing between spots on infected leaves
• Leaf drop
Prevention is the best approach for controlling blackspot. Purchase resistant cultivars of roses. Use drip irrigation to avoid splashing water on the leaves. Ensure roses are planted in the sun with good air movement. Don’t crowd plants together in a planting.
Diseased leaves should be removed from the ground and infected plant parts should be pruned out of the plant.
If you choose to apply fungicide you can treat on a 10–14-day schedule. Some
recommended fungicides include tebuconazole (Bayer Disease Control for Roses,
Flowers and Shrubs), myclobutanil (Immunox, Immunox Plus), triticonazole (Ortho Rose
& Flower Disease Control) and chlorothalonil (Broad Spectrum Fungicide, Garden
Disease Control). As always, follow all label instructions carefully.
