A two-year research project by Erfan Vafaie, an entomologist with Texas A&M Agrilife Extension Service in Overton, Texas, was completed recently, and he suggests some treatments for protecting the Crape Myrtle tree. Texas landscape contractors may be familiar with the problem of Crape Myrtle Bark Scale, or CMBS, an invasive species of insect from Asia which infects Crape Myrtles.
The CMBS secretes a sugary solution, known as honeydew, which causes black mold to grow along the branches and trunk of infected trees. While not fatal, it is unsightly, and Vafaie has been studying the issue in conjunction with collaborators in College station, Huntsville and Dallas. He has found that the numbers of CMBS young peak between the middle of April and the start of May.
Contact sprays like Bifenthrin can be applied once when CMBS ‘nymph’ populations peak, with a follow-up treatment for best results. “Separate treatments in two-week intervals are good, because you want to target bark scale in their immature state,” Vafaie said. “You hit them during the peak, and then again two weeks later, to catch those that have emerged after the first treatment.”
Systemic treatments are also viable, but they need to be applied earlier to be effective, in the second half of March. “You want to have a systemic like imadacloprid or dinotefuran that will be taken up into the plant,” he said. “So that by mid-April to the beginning of May, it will be present higher in the tree when the bark scale are feeding.”
Vafaie says that further research will allow them to hone in further, and develop more control strategies. “We’re collecting data this year and in subsequent years, to try and better understand how different temperatures during those years affect bark scale numbers,” he said.