Beetles defoliate invasive salt cedar
Beetles are chomping their way through salt cedar at Lake Meredith in Texas.
Jerry Michels is most encouraged. The Texas AgriLife Research entomologist, Amarillo, is hopeful this will be the year that salt cedar beetles do some major defoliation to the
water-robbing salt cedar trees that line the banks of the waterways leading into Lake Meredith.
The Plum Creek recreational area at Lake Meredith is the site of Michels’ biological control of salt cedar study. North of Amarillo, Lake Meredith serves as a crucial water source for 11 member cities of the Canadian River Municipal Water Authority.
Salt cedar is a highly invasive plant that uses an incredible amount of water and degrades the environment it is in. Michels notes the plant is usually found in riparian areas where there is a good source of water.
Kent Satterwhite, Canadian River Municipal Water Authority general manager at Fritch, says they have sprayed more than 20,000 acres of salt cedar along the waterways that lead into Lake Meredith, trying to control the invasive tree.
• Texas entomologist studies beetles’ effect on salt cedar near Lake Meredith.
• Salt cedar absorbs great amounts of water from its surroundings.
• The beetles’ emergence this year is encouraging.
“We’re convinced that what we’ve sprayed so far has used more water than all of our member-cities combined,” Satterwhite says. “So it’s a huge water-hog, and the goal here is to try to help Lake Meredith and get some more water into the lake.”
The goal, with the water authority’s support of Michels’ salt cedar beetle study, is to maintain what has already been done, Satterwhite says. The beetle’s emergence and activity this year is encouraging.
Michels says without the support of the Canadian River Municipal Authority, he probably would not have gotten the project started. Not only was the funding important, but so was access to protected sites where “we knew we could release these beetles and they wouldn’t be disturbed.”
The project began in 2004 when Michels first released some beetles that feed on salt cedar, but he notes he has had varying degrees of success over the years.
“Some of our earlier releases may have been with the wrong species of beetle or the wrong ecotype, [or] came from the wrong area of the world,” he says. “For some reason, they just didn’t sit well in this situation.”
From Crete to Texas
But things look better now.
“Over the years, we’ve made various releases of the beetle around Lake Meredith, and we think we finally have a good establishment of a beetle that came from Crete, an island off of Greece,” Michels says. “The latitude is one of the most important considerations that we have, because the beetle’s reproductive system is based on photoperiod.”
The researchers now know that if there is not enough hours of light during the summer, the beetles will think it is going into fall, and they will start to hibernate early by burrowing into the ground. Then they starve to death during the winter.
“But we think we’ve got the right biotype now, and it’s taken off here at Plum Creek and has done some extensive defoliation,” Michels reports. “This is the second summer they have come out of hibernation; they spent the winter here.”
He says even in last year’s drought, the beetles seemed to flourish. And now, they have emerged early this spring and are showing signs of mating.
Beetles can do a lot of damage to salt cedar trees in just one season, he says. The adults and larvae girdle twigs, causing complete defoliation of even mature trees.
“Of course, if you have a big healthy tree, it’s going to take a couple of years of defoliation to actually kill it,” Michels allows. “But smaller trees and seedlings could be killed in the first season.”
Michels says while he is excited to see the beetles emerged for the second year in a row, he knows it is an ongoing process that will take time to see significant results.
Ledbetter is with Texas A&M Agriculture Communications, Amarillo.
This article published in the July, 2012 edition of THE FARMER-STOCKMAN.