Hi, 

Did you mean to attach more photos of the other plants? We only received 1 picture of the crapemyrtle. Do the other plants have different issues, or the same black coating?

The black coating you see on the leaves is called sooty mold ,and it is a fungal growth that occurs on honeydew. Honeydew is a substance that sap sucking insects produce, and in this instance, it could be the scale that we can see on the bark or it could be coming from an overhead tree that may have Spotted Lanternflies, aphids, or other sap-feeding insects on it. The insects suck sap from the plant stems or leaves, excrete the honeydew, and then the sooty mold grows on it. Generally, the sooty mold is harmless, but in some cases, if it's really thick, it can block the plant from receiving sunlight and photosynthesizing, which is how it receives food. The sooty mold will where off eventually with rain and weather, or you can spray it off with a hose, but it isn't necessary. 

Crapemyrtle Bark Scale (CMBS) is becoming more of an issue in our state with the warming climate and the abundance of crapemyrtle trees and shrubs that are planted. These are the white bumps on the stems and branches you see. We are still studying the number of generations and how to best manage the insects for our area. The positive side is that they tend to be eaten by ladybug larvae and some other beneficial insects and wildlife. The link provided will explain how and when to best treat the scale, and in some cases, hiring a professional will be necessary. 

If you would like to send other photos of the plants that you mentioned, feel free to attach them in a reply. 

Emily



Thank you for sharing the additional photos; unfortunately, the files are too small for us to see enough detail. (Images are best when at least 1MB in size per picture.)

The spiky white objects among the scale would be a beneficial predator -- some species of ladybug that specialize in eating scale have a body coating of white wax that mimics how the scale look. There is an image example and a link to a short article about this ladybug on the crapemyrtle bark scale page Emily linked to, if you want to learn more.

Lilacs often look very bedraggled this time of year. Aside from any sooty mold growing atop the leaves (perhaps from Spotted Lanternfly feeding around/above them, or from honeydew from the scale, if the crapemyrtle is next to the lilac), it's common for them to develop fungal leaf infections. Old branches on lilac also naturally decline over time and fail to flower well, though part of that may be insufficient sunlight, as lilacs require full sun to thrive and bloom well. (Full sun would be 6-8 or more hours of direct summer sun.) Lilac should be renewal pruned periodically, which means cutting down the oldest, thickest stems so new growth emerges the following year that will be more vigorous and (when old enough) which will produce more blooms. You can learn more on our lilac diagnostic page.

The white-edged shrub pictured looks like a variegated Japanese Euonymus. If there are white or brownish flecks stuck to its leaves, that is probably a different scale insect called, appropriately, Euonymus Scale. This category of scale, sometimes called armored or "hard" scale (unlike the "soft" or "felt" scale group that the crapemyrtle species belongs to), requires a different tactic to control. Management options are included on that web page, and may involve the use of insecticide unless you are willing to cut the plants back drastically and see if lower-toxicity sprays applied at the right time of year can suppress them effectively enough. If the roots of the Euonymus are otherwise healthy, the plants should regrow well, as it tolerates periodic heavy trimming.

Scale insects often overwhelm plants that are stressed, even if stress symptoms haven't become obvious. Stress can include getting too dry during drought, being pruned too heavily regularly (say, yearly), having a limited root zone (if they are close to a building or paved area), and being exposed to added heat (also from a nearby wall, solid fence, or paved area that absorbs and reflects heat in summer).

The boxwood issue is likely different, but it's hard to see enough detail in the photo to determine what is going on. Common culprits of dieback and leaf loss in boxwoods include Boxwood Leafminer, Volutella Blight, and Boxwood Blight, the latter two of which are fungi, but different pathogens. All three are addressed in our boxwood diagnostic page. Here too, over-trimming (if the boxwoods are sheared regularly) can predispose them to problems.

Arborvitae that lose foliage to the point that branches become bare will not grow foliage back in those areas. Unlike boxwood, holly, and some other broadleaf evergreens, needled evergreens usually do not have dormant buds present on the branches that can fill in with new growth when older growth is lost from pest or disease damage or removed via pruning or deer browsing. If deer did not consume the foliage (they readily eat Eastern Arborvitae, Thuja occidentalis, but usually bypass Western Arborvitae, Thuja plicata). Oriental Arborvitae (Thuja/Platycladus orientalis) is probably eaten too, but we have less information on its deer palatability.

Bagworms are the most common insect pest on Arborvitae, and can strip an area of foliage if the population is high enough. These caterpillars only have one generation per year, but it's critical to catch them early if you're going to use an insecticide, as some of the lower-toxicity spray options won't work if the caterpillars get too far into their development.

Arborvitae can also suffer dieback from soil moisture extremes (they are not very tolerant of soil that gets too dry or too saturated for a period of time), though usually that turns foliage a sickly olive-green and then brown color rather than missing leaves because they fell off.

Miri