Lenhardt, M.1; Stacey Jones2
1Agriculture Agent, Horticulture, NC State Cooperative Extension, NCSU, Statesville, NC, 28687
2Area Specialized Agent, NC State Cooperative Extension, NCSU, Concord, NC, 28025


Research Objective and Methods: Crape Myrtle trees in North Carolina have a new pest, the Crape Myrtle Bark Scale (CMBS). In the spring of 2017, a nursery grower in Iredell County was concerned about this new invasive scale damaging his nursery stock, and went to a County Commissioners public hearing to express these concerns.  Cooperative Extension was contacted to address this need.  A collaboration was formed to research this issue and to determine the most effective treatment times and products to be administered. The experiment was setup in a complete block design with four replications of six treatments. To monitor crawlers, double-sided sticky tape was placed on infested branches of the tree at breast height.  The tape was replaced weekly though the growing season on all treatments, and biweekly through the winter only on control trees. Tape was placed on grid paper to be counted to monitor the insect life cycle and chemical efficacy.

Research Project and Educational Results: CMBS workshop result surveys from 205 residential and green industry professionals resulted in a 78% overall practice change intent to: start or increase recommended CMBS chemical applications, apply treatments at the correct time of year, correctly identify CMBS and symptoms before treatments, use recommended irrigation and/or proper cultural practices (IPM), and to avoid transporting any plant material that may have CMBS on it.

Results and Raw Conclusions: Significant population differences were observed between different insecticide treatments as compared to the control.  Excluding the control and contact insecticide treatments, there was not a significant difference between systemic and insect growth regulator treatments. CMBS can cause severe limb dieback and greatly reduce the aesthetics of crape myrtles.  However most of the crape myrtles that were heavily infested were able to withstand this damage and put on new growth the following spring.  In the first year of the project, the Twice Stabbed lady beetle was the main beneficial insect.  However the second year other species of lady beetles were noticed.  Nymphs over-wintered and were active even during below freezing temperatures, and females generally matured in March.

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