They sweep across the Lower Rio Grande Valley like bomber pilots, scanning the landscape for their targets. Every year, billions of diamondback moths, each about the size of a thin housefly, find and destroy their prey, usually cabbage, causing millions of dollars in crop losses.

To reduce the damage, Dr. T-X Liu at the Texas A&M Agricultural Research and Extension Center in Weslaco is studying the behavior of the insects. His goal is to someday divert and deter them from lucrative vegetable crops.
"As diamondback moths fly along looking for a place to lay their eggs," said the Integrated Pest Management entomologist, "they first look for the color of the plant that attracts them. As they move in, they start looking for the right smell from a plant. And when they land, they test the plant using mouth parts and sensors on their legs. If they like it, they make themselves at home and lay eggs. The larvae that hatch, not the adults, then feed on the cabbage."

Larvae eat large holes in cabbage leaves, reducing or ruining their value.

Diamondback moths are controlled on cabbage and other cole crops with a variety of products designated by the Environmental Protection Agency as either no-risk or low-risk insecticides.

Some contain fungi-derived materials that are toxic to pests when ingested or may contain bacteria that release fatal toxins in the pests' digestive tracts. Others repel pests with botanical ingredients and still others cause starvation.

These products have proved outstanding in the control of diamondback moths, Liu said, but insects eventually develop resistance to even the best insecticides.

By knowing their likes and dislikes and what attracts and repels them, Liu is confident science and the industry can stay ahead of diamondback moths.

"If we can better understand their life cycles and behavior, we can mix and match these repellents and insecticides, adjust the application and timing of sprays so that we can maintain control while avoiding resistance," said Liu.

A visiting scientist from China who spent the last four months working in Liu's lab in Weslaco discovered behaviors of diamondback moths that could help in future insect control, Liu said.

Dr. Shu Sheng Liu (no relation) is the director of the Institute of Applied Entomology at Zhejiang University in Hangzhou, China. His work with T-X Liu will soon be published in scientific journals.

"First, he found that if a cocoon is sprayed with a known effective repellent, the emerging adult will actually like the repellent and be drawn to it," said T-X Liu. "He also found that if a moth is exposed to the repellent within minutes of emerging from the cocoon, it too will be attracted to the repellent. But, if exposed after a relatively longer period of time, the moth will be repelled by the repellent."

Liu said more studies are needed but such discoveries could lead to strategies such as spraying repellent on part of a cabbage field to divert pests to another area where any variety of control methods could be used.

"It's all part of the ever-changing game called Integrated Pest Management where we use several tools to safely and effectively control pests so that our food supplies remain inexpensive, nutritious and plentiful," Liu said.