Abnormal Growth on Knockout Rose in Bristol, TN

Rose rosette is a serious virus disease of roses (Rosa spp.). Over the past 3 years ago gardeners have experienced losses of popular shrub roses. The disease continues to gain ground across the U.S. Rose nurseries are working feverishly to find a solution.

Landscapers and gardeners should inspect all garden roses, including hybrid tea, grandiflora, floribunda, polyantha, and the popular shrub roses such as Knockout™, Home Run™, Carefree™, Drift™, etal. The virus disease is spread by an eriophyid mite while feeding from infected to healthy roses. This tiny mite is a very common plant pest over a large geographic area and is often missed by landscapers and gardeners.

Inspecting your roses weekly and removing all suspicious growth are the best measures for managing rose rosette. Pruning includes complete removal of infected rose canes (shoots) to the main trunk or close to the ground. Deposit all prunings in the household trash. Do not throw diseased canes in a rubbish or compost pile.

Apparently, the disease has no soil borne activity. If you have lost roses to the disease, dig out and properly dispose of the shrub. You can replant another rose in the same planting hole.

Managing eriophyid mite populations requires biweekly spraying with any of the following insecticides and miticides: Cygon 2-E™ (dimethoate), bifenthrin, carbaryl (Sevin), and Avid™ (abamectin).

Continue to review updates about rose rosette disease.