Crape myrtles are a common sight in East Texas. Introduced from China into the United States in 1747, they became even more common with the introduction of the Japanese crape myrtle in the 1950’s. These crape myrtles are more cold hardy, resistant to powdery mildew, and have a reddish-brown bark that peels. Eventually, the U.S. National Arboretum bred crape myrtles to combine the best features of both types. Many of the crape myrtles sold today came from this breeding program.
Crape myrtles are lovely any time of the year, with large colorful blooms in summer and dramatic bark in the winter. Many people still cut off the tops of their crape myrtles, but more and more understand that topping is not necessary and actually degrades their lovely winter silhouette.
If it is not proper to top crape myrtles, how do you prune one? Actually, mature crape myrtles need little to no pruning. Start by looking at the bottom of the tree, and don’t start pruning from the top. Simply cut out any dead branches, and any branches that cross. Prune small limbs off the main trunk and branches instead of cutting them in half. Basically, you just want to limb up your tree and allow it to keep its natural shape.
Now is the perfect time to prune your crape myrtles before the weather gets warm. If your crape myrtles have been topped, it will be almost impossible to return them to their full glorious natural shape. You can cut them off at the bottom and begin again with new shoots, but it is a time-consuming process.
If your crape myrtles have developed the dreaded crape myrtle bark scale, it is recommended that you wait until the tree is actively growing, ideally around bud break, to apply a soil drench of systemic insecticides. Imidacloprid, thiamethoxam, or dinotefuran are some of the chemicals you may wish to look for. Be certain not to apply the drench before or during bloom since it may affect pollinators. It takes approximately 60 days for the drench to be taken up by the roots and dispersed throughout the plant. A second drench the following year is recommended.
You will need to wash the tree’s trunk and main limbs should black sooty mold be on your tree. This mold will remain, even after the death of the scale insects. If you do not wish to use chemical drenches, dormant horticultural oils can help, but may not be enough to control an infestation. Additionally, certain ladybugs may eat the scale bugs, but sometimes are not present in the numbers needed to control your scale population.
These scale insects can be transported by the wind, from humans, birds, or other insects. However, two of the most common methods of transportation is by maintenance equipment and new plantings which are already infected. So, properly pruning your crape myrtles may not only keep them looking beautiful, but may help keep them from acquiring crape myrtle bark scale.