Remote monitoring may save crapemyrtles from invasive pests

The crapemyrtle bark scale is an insect pest that destroys trees by feeding on their sap. The insect has long mouth parts that penetrate the tree bark, and a protective wax on its back that shields the pest from insecticides. After it was introduced from Asia to Texas in 2004, the invasive insect has rapidly spread across 17 states in the Southern US.

In a new study from the Texas A&M College of Agriculture and Life Sciences, researchers have developed a remote system to identify host plants of crapemyrtle bark scale. The monitoring system, which uses electrical penetration graph (EPG) and custom software, could potentially eliminate the need for intensive greenhouse studies.

According to the researchers, crapemyrtle sales have an annual economic value of $69.5 million. The crapemyrtle bark scale has managed to cut this market in half. 

“It’s imperative to control this pest because it can spread quickly and potentially threaten the green industry and ecosystem,” said study lead author Dr. Bin Wu. “Our research is to figure out the host range, or what kind of plant species besides crapemyrtle are exposed to this.”

Using the EPG monitoring system, the team can track the probing activities of the insect. The EPG waveforms allow the researchers to observe what nutrients the crapemyrtle bark scale insect extracts from its host.

“Through those observations and determining what nutrients were being taken away, we were able to consider which were most likely host plants,” explained Wu.

Study co-author Dr. Runshi Xie said scale insects such as the crapemyrtle bark scale are interesting species with diverse genetic systems, and some of them reproduce asexually.

“The female leads a very sedentary lifestyle,” said Xie. “They are pretty much waiting on the male, which is a fly, to instigate mating behavior. For the male to find a female, the female must release a sex pheromone. Our next research project will seek out what compounds are released, and how to use them to disrupt mating.”

“Right now, the control of this insect is the use of systemic pesticides. But the insects are protected by scale covering, which makes spraying ineffective. To treat chemically, we need to drench the soil to deliver the chemicals into plants, and insects feeding on the sap will die. However, this practice is also detrimental to pollinators. Our focus will be to see if we can come up with novel systems that control insects without relying too much on pesticides.”

The study is published in the journal Insects.

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By Chrissy Sexton, Earth.com Staff Writer