Welasco, Texas
June 14, 2004
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. |