Report instances of found crape myrtle bark scale
A constantly updated map showing the spread of crape myrtle bark scale helps Mississippians stay aware of this treatable pest that threatens the beauty of one of the state’s most common landscape shrubs.
Crape myrtle bark scale -- or CMBS -- is an insect pest that was first reported in Mississippi in 2015 after being found in Texas in 2004. It has spread across the Southeast and beyond, appearing as white or gray felt-like spots on the bark of crape myrtles. Heavy infestations involve tens of thousands of individual scales, covering large areas of bark on trunk, limbs, branches and twigs.
Underneath the felt-like covering, the scale appear to be pink. As they feed on the trees, CMBS exude mass quantities of excrement, called “honeydew” because of its high sugar content. This honeydew rains on everything below and is the food source for sooty mold.
Sooty mold, a type of fungus native to Mississippi, grows on the honeydew and turns everything black.
Gary Bachman, a horticulturist with the Mississippi State University Extension Service and host of “Southern Gardening,” first found CMBS in the state in Ocean Springs.
“Perhaps the first sign of an infestation you might see is what alerted me to it,” Bachman said. “It is fairly easy to spot the presence of scaly, flaking patches of black, sooty mold on the tree itself.”
This pest can infest trees in prodigious numbers.
“Individual crape myrtle trees will usually not die from a CMBS infestation, but they lose their beautiful appearance in the same way as improper crape myrtle pruning destroys the appealing architecture of the trees,” Bachman said.
Blake Layton, Extension entomologist, said light to moderate infestations make trees unsightly because of the honeydew and sooty mold they produce.
“Heavy infestations reduce bloom and growth, can cause limb die-back and can even kill trees. This is rare, but it happens occasionally,” he said.
Layton said people need to know how to recognize these pests so they can be reported, and their spread tracked and even slowed.
“If you think you have these pests on your crape myrtle, the best thing to do is call your county’s Extension agent, and then the agent can alert me,” Layton said. “This will get the agents involved and make them aware they have CMBS in the county.”
To date, CMBS has been detected in 22 Mississippi counties. MSU Extension updates a map that shows which counties have the pest and indicates where the pest has not yet been discovered.
Layton said that prevention is the best way to control this scale pest.
“Avoid bringing infested plants into an area or landscape in the first place,” Layton said. “Work closely with your nursery or landscape contractor to be sure any crape myrtles you purchase are CMBS free.”
Trees that are already infested with CMBS can be treated successfully
with systemic insecticides such as imidacloprid, dinotefuran or thiamethoxam applied as soil injections or soil drenches.
“Late March through May is the best time to treat, but treatments can be applied anytime an infestation is detected and trees are still actively growing,” he said. “Because these treatments do not give 100% control, plan on treating trees again the following year -- even if you don’t see any scale.”
Find more information on CMBS detection and control at https://extension.msstate.edu/sites/ default/files/publications/publications/p2938.pdf.