New Ornamental Pest Alert!

— Written By and last updated by JoAnne Gryder

Occasionally, new insect pests and diseases of ornamental trees and shrubs are accidentally introduced to the United States. New pests can present problems since gardeners are not familiar with the pests and the damage they cause. Two new diseases, rose rosette and boxwood blight, are already in Wilkes County, while one insect, the emerald ash borer, may be in Wilkes County soon.

Rose rosette is starting to show up on local roses. This disease is a virus and no roses seem to be immune to it, not even Knockout roses. Symptoms include distorted leaves, and distorted buds and blooms. Other symptoms are abnormal, red discoloration of shoots and clustering of shoots called witches broom. The only effective way to deal with this disease is to pull the infected plant up and dispose of it.

Boxwood blight showed up in Wilkes County a few years ago. This disease is a fungus that causes circular brown lesions on leaves and cankers on boxwood stems. Eventually the shrub will drop leaves and, left untreated, the plant will die. Boxwood blight spores are sticky and can be spread by infected tools or through human contact.

Like rose rosette, infected plants should be removed from the landscape and destroyed. Sanitation practices like disinfecting garden tools and not working on wet plants will help prevent the spread of this disease.

emeral ash borerEmerald ash borer is a beetle that bores into ash trees. This pest has not been found in Wilkes, but it has been in counties close to us. The larvae that hatch feed under the bark of the tree, which disrupts to flow of water and nutrients. This damage will eventually kill the tree in a couple of years.

Symptoms of emerald ash borer infestations include the tops of the trees starting to die. Sometimes woodpeckers will cause damage when they attempt to feed on the larvae below the bark. The easiest way to tell if you have borer damage is to look for D-shaped exit holes on the trunk. Cutting down infested trees and chipping or burning the wood is the best way to deal with this pest.

Written By

Photo of Bill Hanlin, N.C. Cooperative ExtensionDr. Bill HanlinHorticulture Assistant (336) 651-7333 william_hanlin@ncsu.eduWilkes County, North Carolina
Updated on Dec 7, 2016
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