The crape myrtle is one of the more desirable landscape plants in our area because of their pleasing aesthetics and the generally low maintenance that they require. Because of these desirable traits these trees can be found widely throughout the region. Unfortunately, there is a new insect pest that has found its way to our area that can make crape myrtles both unsightly and require more maintenance.
This pest is the crape myrtle bark scale (CMBS). This scale insect was first found in Mississippi in 2015 and has spread to over 20 counties since. Recently, crape myrtle bark scale was found in Benton County. Crape myrtle and American beautyberry are the only host that this pest has been found on in America.
Although infestations of CMBS generally won’t kill trees, they cause the trees and the surrounding landscape to become unsightly. CMBS nymphs produce large amounts of honeydew when they feed on the crape myrtle, which is a great growing medium for sooty mold. This black sooty mold will grow anywhere that the honeydew falls including the tree itself as well as anything under the tree such as mulch or other landscape plants. While this mold doesn’t cause any adverse health effects, it can quickly cover the tree and the area under it and turn it into an unsightly mess. Heavy infestations of CMBS can also result in fewer and smaller blooms.
One of the biggest issues surrounding CMBS is lack of natural enemies. While there are some lady beetles that will prey on this pest, the population of lady beetle usually can’t grow to a level that will give effective control. This leaves us with only four effective routes of control. The first method is exclusion by intensely inspecting any new crape myrtles that you intend on planting in the landscape for CMBS. If you find that a crape myrtle is infested with CMBS you should not buy or plant it. The second is plant selection. When selecting plants for your landscape, consider planting different species other than crape myrtle. The third is destruction of infected plants. This may seem drastic, but it may be the best option depending on your situation. If you decide to remove an infested plant, always take precaution to not spread the pest from the plant material. Burning or burying of removed plant materials should happen as soon as possible and always cover the material with a tarp when transporting to reduce the chance of wind dispersal of CMBS in transit. The last method of control is chemical control. There are chemicals that will give control of CMBS, thought they will not give 100 percent control and will require subsequent applications. The most effective control comes from systemic pesticides that are applied as a soil drench. These types pesticides will need to be applied yearly. Always follow label directions when using any type of pesticide.
If you would like more information about identification and control of CMBS, please contact the Benton County Extension Office at 662-224-6330.