Being a gardener in Florida is exciting. We have many plants to choose from and the weather is mostly pleasant but always seeming to surprise us. One disadvantage of living in such a place, in addition to having so many growing zones, landscape nurseries, and major shipping ports, is that invasive species that land in Florida don’t like to leave. One newcomer in the lineup of invasive pests is the crape myrtle bark scale (Acanthococcuslagerstroemiae). This invasive insect pest made its way from Texas and, as of a few weeks ago, the only Florida sighting had been in Santa Rosa County. Unfortunately, this pest has now been confirmed in Leon County. Landscapers and gardeners in north Florida should learn how to identify this pest and what options are available for control.
The crape myrtle bark scale, as the name suggests, has a pretty specific host – the crape myrtle (Lagerstroemia spp.). However, in the United States, this scale has also been found feeding on our native beautyberry (Callicarpa americana). Due to the widespread planting of crape myrtles, these should be the gardeners primary focus when looking for this new pest. If present on the tree, it is hard to miss. These scales feed on the bark and are a snow-white color. Being a scale, they produce honeydew that is then covered in black sooty mold. So, if you see a crape myrtle with black branches, look closely and you may see the white scales. If you crush these scales and they leave a pink goo on your fingers, then you very likely have crape myrtle bark scale. Of course, you can send a picture or sample to your local county extension office for confirmation.
Black sooty mold and white scales along the trunk and branches are a tell-tale sign of crape myrtle bark scale. Credit: Mark Tancig, UF/IFAS.
If you do happen to find crape myrtle bark scale in your own landscape, or one that you manage, proper control is important to prevent it from moving along any further. Since scales suck on sap and are protected by an outer shell, systemic insecticides are the preferred product for effective control. These include the neonicotinoids, such as imidacloprid (Merit) and dinotefuran (Safari). The larval stage can be controlled with a horticultural oil, sometimes mixed with another insecticide like bifenthrin (Talstar), however, this will not control the adults. Another option is to completely remove the tree and burn all of the plant material.
Excessive sooty mold has turned these branches black. Be on the lookout for crape myrtles looking like this to help identify crape myrtle bark scale. Credit: Jim Robbins, Univ. of Ark. CES. Retrieved from bugwood.
The crape myrtle bark scale can significantly reduce the aesthetic value of crape myrtles due to the black sooty mold that covers the bark. It is also known to reduce flowering and can lead to thinning of leaves. Since crape myrtles make up a big part of our managed landscapes, let’s all work together to scout for this pest and control it when found. If you have questions, please contact your local county extension office.
Difference in flowering due to crape myrtle bark scale damage. Credit: Jim Robbins, Univ. of Ark. CES. Retrieved from bugwood.
The shorter days and cooler temperatures of autumn bring on changes in our shrubs and trees.
Most people expect to see changes in leaf color in deciduous trees and shrubs during fall. But some people become concerned when the leaves on certain evergreen plants begin to turn yellow with the change in the seasons. For many plants this is normal.
Azaleas may lose a few leaves now. These are the older leaves on the branches near the center of the plant. There is no need for alarm by the loss of a few older azalea leaves from now until spring. However, if the younger leaves, those nearest the tip of the shoot, turn yellow or brown there is cause for concern. Poor drainage, lack of water or alkaline soils may cause this condition. Be sure to keep azaleas and other ornamental plants well-watered during dry weather that may occur from now through spring.
Other plants such as gardenias, hollies and camellias may have yellowing leaves now. But as with azaleas, these are the older leaves on the stem near the center of the plant. The mature leaves will drop from the plant from now until spring. This is only the normal aging of older leaves. However, be careful to not confuse this normal process with spider mites, scale, lace bugs, nutrient deficiencies, poor growing conditions or salt injury. Just keep in mind that this normal change in leaf color and leaf drop occurs on the older leaves generally during cooler weather – it’s a seasonal change.
Young red maple with fall foliage. Photo credit: Larry Williams
The leaves of sycamore trees have changed from green to brown by now. Although the sycamore is a deciduous tree, this phenomenon may not be caused by a change in day length or temperature alone. This change in leaf color in sycamores can begin in late summer. Many times, it is the result of sycamore lace bugs feeding on the leaves. By the time the damage is visible, there is little that can be done to correct the problem. However, this problem will take care of itself since sycamore trees will soon be dropping their leaves.
We do have some trees that exhibit beautiful fall foliage this time of year. A few to consider include hickory and gingko for their bright yellow fall foliage, black gum for its early display of brilliant red, purple or orange leaves and Chinese pistache for its late reddish-orange fall show. There are plenty of other good trees to consider for fall color here in North Florida such as dogwood, crape myrtle, Florida maple, sourwood, shumard oak and the list could continue.
Crape Myrtle season is almost upon us. Soon, every roadside, landscape, and gas station parking lot in the deep south will be lit up in gaudy colors from white to hot pink to fire engine red. A well-placed Crape Myrtle (Lagerstroemia hybrids) can turn even the most boring landscape into a picturesque photo op once summer rolls around. These toughest of flowering trees also ask very little of gardeners to look their best, thriving in many varied settings with a wide range of care given to them. Despite their low-maintenance nature, I see all too many Crape Myrtles languishing in landscapes. While it is difficult to fail with Crape Myrtles, it is not impossible if you site and maintain the trees incorrectly. This summer, follow these three tips to get the most out of the best small tree a southern landscape can offer.
Properly sited, pruned, and maintained crape myrtle. Photo courtesy of Daniel Leonard.
Do not murder your Crape Myrtles. For any reason. No other tree gets lopped off each year to a random height in the belief that it makes it prettier. While your “murdered” crape may indeed produce more flowers the following season, you are permanently damaging the tree, giving rot and decay a foothold, unnecessarily making the tree more susceptible to storm damage, and ultimately shortening the tree’s lifespan. The only pruning that should be done to the species is an occasional “limbing-up” to expose the gorgeous flaky bark underneath and to remove dead or dying branches.
Don’t plant Crape Myrtles in shade. Crape Myrtles perform their best in 6+ hours of blistering full sun per day. Even light shade at various times during the day will greatly reduce flowering, cause the tree to appear thin, and force it to reach for the sun, creating a leggy look. There are many wonderful small landscape trees like Greybeard, Redbud, and Japanese Magnolia that make excellent Crape Myrtle alternatives in shady sites. If you can’t put a Crape in full sun, plant something else.
Keep the area under the canopy free of turfgrass. Turf is a wonderful feature in lawns, just not directly under crape myrtles. Grass does an excellent job of scavenging nutrients and water that otherwise would benefit the crape myrtle above. Also, having grass inside the dripline forces homeowners and landscape professionals to cut the grass right up to the trunk. This often leads to soil compaction from heavy mower traffic and damage from lawnmower decks and string trimmers, which damages the thin Crape Myrtle bark and can even girdle and kill the tree. Either kill out the grass and weeds under the canopy with a nonselective herbicide like Glyphosate and then mulch or plant a shade loving groundcover like Asiatic Jasmine.
Crape Myrtle is one of the most rewarding plants Panhandle gardeners can grow as well as one of the easiest. By following just a few best practices, not overpruning, planting only in full sun and keeping the ground free of turfgrass under the canopy, pretty much every landscape can enjoy success with the species. For more information on growing Crape Myrtle and other gardening topics, reach out to your local UF/IFAS County Extension office! Happy Gardening!
