Can I control the aphids on my crape myrtles without hurting the ladybugs?

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Question Can I control the aphids on my crape myrtles without hurting the ladybugs?

Answer Crape myrtle trees originally came from Asia. Now they are grown all over the world. Crape myrtle aphids were originally discovered in Hawaii. Now they are found all over the world on crape myrtle trees.

Since this aphid was found in Hawaii, it was given a Hawaiian scientific name - Tinocallis kahawaluokalani. If you say the last part slowly (ka-hawa-lu-o-ka-lani), then you will find your hips start to sway as if you are wearing a grass skirt.

This aphid only feeds on crape myrtle trees. It pierces the leaves and withdraws the tree’s sugary sap. Since the feeding aphid withdraws more sugar than it can use, it excretes a sugary substance we call honeydew (not to be confused with the infamous list called “honey do”).

Large aphid populations can cover the leaves of a crape myrtle with honeydew. Airborne sooty mold spores land on the honeydew and use it as a food source. Soon the crape myrtle leaves are black from the sooty mold fungus. This relationship to sooty mold is the primary reason people want to control crape myrtle aphids.

A new ladybug has been released in the US. This ladybug, named Harmonia axyridis, is very good at finding and eating aphids. However, sometimes an aphid population may be causing problems that need to be addressed before the ladybugs can get them under control. In this case, there are a few solutions that will minimize damage to the ladybugs.

Orthene 75S (acephate) is an insecticide that can be painted (also called banded) onto the trunk of the crape myrtle. It will be absorbed by the tree and transported to all the leaves. No spraying is necessary, yet total control of the aphids will be achieved. Read the label for mixing and banding instructions.

Bayer makes a product that is also moved systemically throughout the tree. It is called Tree & Shrub Insect Control. Simply mix this product with water and pour it around the tree. This product will also provide complete control. Read the label for specific mixing instructions.

Lastly, a spray application of horticultural oil or dormant oil in the winter will kill the overwintering aphid eggs. Simply wait until the leaves fall off the tree and apply one of the oils. The aphid eggs will be suffocated by the oil.

By applying one of the systemic products prior to leaf drop, the aphids may be killed before they have chance to lay eggs. September would be a great time to initiate that control option. For more info about crape myrtle aphids, go to http://www.ces.ncsu.edu/depts/ent/notes/O&T/shrubs/note31/note31.html

If you don’t have internet access, then call the Extension Office at 893-7533 or email me at gary_pierce@ncsu.edu

Mele Kalikimaka (pronounced meh-leh kah-lee-kee-mah-kah) may be the thing to say on a bright Hawaiian Christmas Day, but kahawaluokalani is the thing to say if you have crape myrtle aphids. To get your brain stuck on a song, visit http://hometown.aol.com/jesusandsue2/ChristmasHawaii.html

Gary L. Pierce

Horticulture Extension Agent

Harnett County