Tiny Mite Causes Big Problems on Roses

— Written By Donna Teasley and last updated by
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One of the most popular landscape plants of southern gardens is the Knockout Rose. This rose, comes in several colors, blooms profusely and seems oblivious to most of the normal rose bush problems such as black spot. But there’s always a hidden thorn (pun intended) and although the Knockout is a great plant, there is a serious disease to which they show no immunity: Rose rosette disease or witches broom of rose.

Rose rosette is actually a virus and is spread by tiny wingless mites that ride air currents until they find any type of rose. They prefer the wild multi-flora rose which is a pest across the country. But they also like other roses also, including the Knockout. Because we have so many Knockout roses planted in area gardens, we are seeing a rise in this disease. Eriophyid mites lay eggs on new growth throughout the spring and summer but their danger to our roses is the virus they carry on their bodies. Viruses have no cure and once infected, small bushes can live in decline, a couple of years with large plants holding on for about 5 years.

Symptoms, which are showing up now through mid-July are clumps of reddish growth with many thorns and deformed, crumpled and crinkled growth with red and yellow pigmentation. This is where the name witches broom comes from.

If noticed, get rid of the plant immediately. Cover the plant with a plastic bag, then saw it off at ground level and dig out the roots. Burn or bag dead plants. Wash tools and change clothing before coming in contact with healthy plants.

  • Plant rose bushes at least 300 feet from wild roses
  • Don’t plant bushes too close and interplant with other plants
  • Control mites by pruning hard in late winter and spraying with insecticidal soap through mid-July. Bag pruned branches.

If you have plants with rose rosette disease, don’t procrastinate. Get rid of infected plants immediately as the virus will spread to other roses.

If you aren’t sure that you have this disease, you can bring a sample by the Extension Office or email a photo to donna_teasley@ncsu.edu.