Now that summer is upon us it is important to inspect our landscapes for possible insect and disease infestation. It is typical at this time of year to see many insect and disease issues affecting our trees and shrubs because it is hot and insects are in flight, however this appears to be a particularly bad year in Texas. What we are seeing this year is a heavy infestation of aphids, spider mites, leaf spot and scale affecting Crape Myrtles and Indian Hawthorns.
What is a Crape Myrtle?
Crape Myrtles’ are a type of tree that can be found in the southern US. They usually grow up to 15 feet tall and they bloom for almost 120 days. The only type of Crape Myrtle that grows taller is the Red Crape Myrtle that can reach a height of 30 feet. The tree needs full sun light and lots of water. When fully bloomed the foliage of the tree is a bronze green, and the flowers can be found in a mix of pink, red, and white. They can bloom in mid summer, late fall, and mid fall.
Crape Myrtles, Aphids:
Many Crape Myrtles are heavily infested with aphids and leaf spot this year. Aphids are a soft bodied, sucking insect that feed on the foliage of the plant. When they feed on trees and shrubs they cause leaf curling and they leave behind a natural sap that attracts other insect invaders. The sap left behind by aphids, also covers the leaf tissue and prevents it from being able to absorb nutrients.
Signs of Aphid Activity (Aphids, Eggs, Curling Leaves, Browning Leaves)
Seeing eggs on your leaves can be a direct indicator that you have aphids. This is one of a few sure signs that your plant is infested with aphids.
Curling of the leaves and browning of the edges are also common signs you have aphids. If you look at the picture (above) the holes in the leaf itself are from aphids feeding on the juices of the foliage. When the infestation is bad enough the plant will lose foliage, become disease prone and ultimately the plant could even die.
Crape Myrtles, Scale:
Another issue that is affecting Crape Myrtles this year in Texas, is scale. Scale is another insect that on first appearance, looks almost like a small white tic tac on the bark of the tree. Typically the bark that they are residing on will be black due the sap released by the scale. Scale feeds on the tree by sucking the plants juices. The sap that is produced is a waste product that invites more insects. If left untreated, scale will affect the tree by reducing the blooms and the sap that is left behing covers the leaf and restricts the amount of sunlight the plant receives. This prevents photosynthesis and this process can eventually kill the plant.
What is an Indian Hawthorn?
Indian Hawthorn is a medium sized shrub perfect for the southern states. It is very simple to care for and keep neat. The shrub looks great all year round, with it’s main focal point being in the spring when large groups of flowers appear pink and white. This shrub can grow 1 ft to 15 ft and should be planted 10 ft – 15 ft apart from any other Indian Hawthorn plants. It’s foliage is dark green.
Indian Hawthorn, Spider Mites:
This year in Texas we are seeing elevated infestations of spider mites in Indian Hawthorn shrubs. Spider mites feed on the plant juices and their damage can be very severe as they feed on the foliage of the plant and not the bark. Spider mites are a chewing insect so their damage is identifiable when the plants foliage is noticeably chewed away. The open wounds caused by spider mites invites infections caused by disease and fungus. In addition to these problems, spider mites also set up small dense webs on the entire leaf. This is visually unappealing and it also restricts sunlight needed to activate photosynthesis which activates wilting, curl, and premature leaf fall.
Indian Hawthorn, Leaf Spot:
The number one issue affecting Indian Hawthorn (and Red Tips) is Leaf Spot. Leaf spot is a fungal disease that looks like small black circles usually surrounded by red or yellow outer shades. It almost looks like there are cigarrette burns on the leaves of the plant. Leaf spot is usually by wind blown spores that land on the plant. If left untreated leaf spot will weaken the plant which in turn will cause wilting, leaf curl and premature leaf fall. Without leaves, the plant cannot feed itself which can result in the death of the plant.
Tree and Shrub Insects and Disease Programs:
All of the issues noted above are issues that can be prevented with proper tree and shrub care. A good treatment plan for trees and shrubs consists of early spring fertilization, insect and disease applications in the late spring, summer, and late summer, followed by deep root fertilization in the fall and dormant oil in the winter.
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