GREEN Vision

By Mengmeng Gu, Ph.D., and Bin Wu

Beautyberry Again! CMBS in Kansas and South Carolina IN THE SEPTEMBER/OCTOBER issue of TNLA Green, I shared a picture of my own American beautyberry being infested by crapemyrtle bark scale (CMBS) in May 2017. I am sad to report an update on that. Of six branches, one is now heavily infested (See Figure 1). Only the top half of that branch, about a foot-and-a-half long, is infested. At first I saw the black sooty mold on the leaves and when I looked closer, I saw those white egg sacs (See Figure 2). CRAPEMYRTLE BARK SCALE

How do you tell CMBS from crepe myrtle aphids just by looking at the sooty mold infestation? The aphids often feed on the tender parts of a plant, the growing tips, or at least start from there. On a crepe myrtle the growing tips are on the outside of the canopy, so honeydew secreted by aphids often drops to leaves, where sooty mold will grow. In contrast, CMBS feeds on bark or twig, inside the canopy. Honeydew secreted by CMBS falls on lower bark or twig, so the sooty mold is often on the lower bark or twig, still inside the canopy. Of course, there are always exceptions; on a heavily aphidinfested plant you may find sooty mold everywhere. Different from a crepe myrtle plant, an American beautyberry doesn’t have a main trunk or closely clustered branches.

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TNLA Green November/December 2019

Figure 1

That is probably why sooty mold from CMBS is more visible on the leaves. But you can probably tell the sooty mold concentrates on the part of the leaves close to the stem, where CMBS feeds (See Figure 3). Also interesting is that there are some males on the back of the leaves. You can tell them apart from the female ovisac by their smaller size and cylinder shape. Interesting enough, the nearby crepe myrtle did not have nearly as many CMBS as the beautyberry. Instead, there’s a big

aphid infestation, probably due to the rain we have been getting recently. What do you think would be the best control strategy for me? Considering only the top half from one of the six branches was heavily infested, I think I will just cut it off. That will significantly reduce the infestation source. Another important integrated pest management strategy is not introducing infestation in the first place. I live within walking distance to a box store garden center and often inspect their plants,