Bark and Systemic Insecticidal Control of Acanthococcus (=Eriococcus) lagerstroemiae (Hemiptera: Eriococcidae) on Potted Crapemyrtles, 2017 Open Access

The CMBS is an exotic pest of crapemyrtle trees in the United States that decreases aesthetic value through excretion of honeydew and subsequent colonization by sooty mold. The sooty mold can cover the bark if infestation levels are high, causing a concern for landscapers and nursery growers. This efficacy trial was conducted on potted crapemyrtles growing on black nursery cloth outdoors at the Texas A&M AgriLife Research & Extension center in Overton, TX from 7 Mar to 27 Jul 2017. The insecticides tested are listed in Table 1.

A total of sixty 5-gal crapemyrtle trees were arranged in a CRD in three rows and irrigated by drip. Trees were all similar in size and had visible signs of infestation at the beginning of the trial (7 Mar). Treatments were either applied as a drench or bark spray, in single or multiple applications (Table 1). Bark sprays were made for full coverage using an R&D CO₂-powered sprayer (Model D-203s) with a 601FA single nozzle spray boom (Bellspray, Inc). Drenches were applied by water and product in a clean bucket and slowly pouring the solution onto the plant medium to avoid overflow. Scale crawlers were sampled weekly using sticky tape on three to five branches (1 cm in diameter or larger). Traps were made by wrapping 3M ¾-inch double-sided permanent sticky-tape around the branch at waist height and replaced weekly. Length of removed tape was measured and scale crawlers counted under the microscope to produce number of crawlers per cm². The values used in the analysis represent averages of counts made from all tape collected from the sampled branches of individual trees. All means were log transformed(log + 1) and compared using an ANOVA and Dunnett’s post hoc test with water check as the control group.

There was no significant difference between any of the treatments and the untreated check prior to treatment applications (Table 2; 03/07). Safari drench and Safari drench + Talstar treatments significantly reduced crawler populations compared with the untreated check by 04/20 (Table 2). By 04/27, Fulcrum, Talus, and Safari bark spray had significantly lower crawler numbers compared with the untreated check (Table 2). By 05/04, Altus-treated trees had significantly lower crawler numbers than the untreated check, as did Mainspring by 05/18 (Table 2). Ventigra + Pure oil, Mallet drench, and Venerate + Grandevo demonstrated late or no suppression of crawlers (Table 2).

This research was supported by the Applied Research and Development Program (grant 2014-70006-22632) from the United States Department of Agriculture National Institute of Food and Agriculture, and industry gifts of pesticides.