October 2016
UTA and TPWD Biologists Study Zebra Mussel Population Fluctuations in Texas Lakes

The invasive zebra mussel (Dreissena polymorpha), which has already invaded at least 13 lakes in Texas, has exhibited changes in population numbers in some of those lakes. Dr. Robert McMahon, professor emeritus of biology at The University of Texas at Arlington and principal investigator on the new grant from the Texas Parks and Wildlife Department, along with Brian Van Zee and Monica McGarrity of TPWD, are expanding their research into the factors that cause these changes.

In three Texas lakes - Texoma, Ray Roberts and Belton - zebra mussels quickly increased in number, followed by a sharp decline. Research suggests the mussels can starve themselves out by removing food and nutrients from the water, and flooding may also lead to a decrease in their numbers. In addition, low calcium concentrations, particularly in East Texas lakes, likely limit infestation by zebra mussels because mussels require calcium to build their shells.

The researchers will use monthly samples from infested Texas lakes to collect data on various population and water quality parameters. "Our study has a special emphasis on understanding the causes of the zebra mussel population collapses that have occurred in Texas lakes and other warm, southwestern water bodies," McMahon said. Van Zee noted, "We've seen that in some reservoirs, they'll eat themselves out of house and home and the population will crash, but then it reaches a stage where they'll come back and the population will stabilize at some level. Once they become established in a reservoir, there's not really a way to eradicate them."

Read more at phys.org.


Credit: Amy Benson, U.S. Geological Survey



Credit: Texas Parks and Wildlife Dept.

New Book Explores Texas' Fraught Environmental History

A new book has been released by Texas A&M University Press that explores the human story that is linked to changes in Texas' landscape. The Texas Landscape Project, written by David Todd and Jonathan Ogren, "is an exercise in visual storytelling, mixing historical and aerial photographs with geographical charts, all of which provide simple and visceral indicators of the sheer amount of change that has occurred across the state," says reviewer Asher Albein. "With over 300 maps, the atlas is a detailed survey of Texas’ ecological challenges. Sections focus on topics such as the colonias of the Rio Grande Valley, wildlife management cooperatives in the Hill Country and flooded ruins of Falcon Lake... What this book makes clear is just how thoroughly humans have woven ourselves into the geography of the state, for good and for ill."

By the way, Mr. Todd is an Invaders of Texas citizen scientist. In another example of the importance of the Invaders of Texas program, he and Mr. Ogren used data from the Invaders of Texas database in their research.

Texas Landscape Project book cover TLP-map

Credit (both): Texas A&M University Press

Contradictory Goals with Texas Invasive Plants

Public radio station KUT recently aired an excellent story about invasive plants in Texas. Reporter Mose Buchele interviewed several professionals, including Dr. Hans Landel, manager of the Invaders of Texas Citizen Science Program and Invasive Species Coordinator at the Lady Bird Johnson Wildflower Center; John Clement of the Austin Watershed Protection Department; and Forrest Smith, director of the South Texas Natives and Texas Native Seeds projects at Texas A&M University-Kingsville. One of the main points of the story is the struggle that occurs as concerned Texans work to control invasive plants while at the same time it is legal for Texans to purchase and plant many of those same invasive plants. Even for those species that are listed on the Texas Department of Agriculture's noxious weed list, which prohibits the sale of the listed plants, the State has little recourse if someone complains about a retailer selling a plant on the list.

Listen to or read the story.


spraying Arundo

Dillon Hendrickson sprays herbicide on a stand of invasive Arundo donax, known as giant reed, plants on Lady Bird Lake in Austin. Credit: Jorge Sanhueza-Lyon, KUT

Popinac Changes Soil Nitrogen Dynamics: Implications for Texas?

The popinac (or white leadtree Leucaena leucocephala) is invading native landscapes in Texas, particularly along the Gulf coast. As with many other invasive species, the tree can form large monoculture stands, crowding out natives. Now, research from Guam has determined that it has a negative impact on soil nitrogen, as well. Soil nitrogen is a very important plant nutrient, and its abundance and availability is regulated by soil bacteria. Typically, it increases under leguminous trees such as popinac, because leguminous plants capture nitrogen from the air, convert it into tissues, and eventually release it to the soil when leaves and other parts of the plant drop to the soil. In Guam, however, popinac somehow alters the soil bacteria community in such a way that the amount of soil nitrogen decreases. This has implications not only for the native ecosystem but for restoration, as well. Resource managers in Texas will now need to incorporate these results into their plans for controlling popinac. Learn more at phys.org.


Credit: Colin Wilson, www.issg.org

Estimated Cost of Invasive Insects to the World Economy

Invasive insects cause at least $75.6 billion(69 billion euros) of damage per year worldwide, say investigators, whose study brought together the largest database ever developed on economic damage attributable to invasive insects worldwide. While this is a staggering amount, the cost is surely underestimated, as the study considered damage to goods and services, health care costs and agricultural losses, but not impacts on ecosystem services or recreation/tourism, and furthermore focused on only the top ten most costly insects. Learn more at sciencedaily.com.


Credit: David Cappaert, Michigan State University

Invasive Spotlight:
Asian Longhorned Beetle
(Anoplophora glabripennis)

This insect, originally from Asia, is a serious threat to many species of deciduous hardwood trees in the United States (e.g., maple, elm, willow, birch, horsechestnut, and poplar). During its larval stage, the Asian longhorned beetle (ALB) bores deep into a tree's heartwood, where it feeds on nutrients. This tunneling damages, and eventually kills, the tree. It has the potential to devastate recreational and forest resources and industries, as well as urban and suburban environments.

ALB is a large, distinctive-looking insect measuring 1 to 1.5 inches long, not including its antennae. These antennae, which give the insect its common name, are as long as the body itself in females and almost twice the body length in males. The insect's body is shiny black with white spots; the antennae are banded in black and white. In Texas it may be confused with the cottonwood borer, which also has a black-and-white pattern. However, the cottonwood borer has white cross-stripes with length-wise stripes as well instead of spots, and it has black antennae instead of the banded antennae of the ALB (see photos at right).

Symptoms of infected trees include unseasonably yellow or drooping leaves when the weather has not been especially dry; dead or fallen branches; dime-sized (3/8 inch or greater) perfectly round exit holes; shallow scars in the bark (egg-laying sites); and sawdust-like excrement (frass) in branch crotches or at the base of trees.

ALB is presently not found in Texas, and let's keep it that way! One way it can infest new areas is through inadvertent transport within infested firewood. Please, do not move firewood: burn only local wood.

Because of its potential negative impacts in Texas, the Asian longhorned beetle is a Report It! species as part of the Sentinel Pest Network, a component of Texasinvasives.org. If you believe you have found an Asian longhorned beetle, please report this species. We also ask that you please collect a specimen to aid in identification.

Follow this link for more information on the Asian longhorned beetle.


Credits: Michael Bohne, Marshall Coulter

    ALB evidence

Top Left: Oviposition site and exit hole (J. Forman Orth, Massachusetts Dept. of Agricultural Services)  Top Right: Frass (City of Toronto Parks, Forestry and Recreation)  Bottom: Exit hole (Joe Boggs, Ohio State University, Bugwood.org)

ALB alert

More News

Invasive Plants Dye Woodpeckers Red
Eastern populations of "yellow-shafted" Northern Flickers (Colaptes auratus) have been appearing with red feathers. A new study has found that the pigment comes from berries of two exotic honeysuckle species that the birds eat. The berries apparently are causing orange feathers in Cedar Waxwings (Bombycilla cedrorum) as well. Learn more at sciencedaily.com.

A New Tool for Wetland Management
"A team of environmental engineers and a wetland ecologist have created a computer model that can help wetland managers increase the size of migratory bird habitat and combat invasive vegetation using existing resources." Learn more at sciencedaily.com.

Is Palmageddon Coming to California?
Recent detection in California of the South American palm weevil (Rhynchophorus palmarum), which has traditionally been found in South and Central America, the Caribbean and Mexico, has scientists, farmers and nursery industry officials worried because it threatens California’s $70 million ornamental palm industry and $30 million commercial date industry, as well as native palms. Learn more at universityofcalifornia.edu and at the Center of Invasive Species Research.

'Snotty Gobble' Could Be Good Weed Controller
A native parasitic plant found commonly throughout southeastern Australia and known as snotty gobble (Cassytha pubescens), is showing great promise as a potential biological control agent against introduced weeds that cost millions of dollars every year to control. Learn more at sciencedaily.com.

Cost-Benefit Analysis of Giant Hogweed Control Strategies in Germany
Determining the balance between costs and benefits of controlling an invasive species is rarely done, yet should be an important consideration when developing policy. Researchers in Germany have produced such a cost-benefit analysis for controlling giant hogweed (Heracleum mantegazzianum), which poses not only threats to native landscapes, but health hazards to humans and limited accessibility to sites, trails and amenity areas. They found that benefits can outweigh costs of control by up to 225 times. (NOTE: Giant hogweed is a Report It! species of the Sentinel Pest Network in the Texasinvasives.org program.) Read the research article.

Ornamental Plants' Potential Benefits for Native Bees, Beneficial Insects
Researchers in Georgia have found that flowering ornamental plants (exotic and native) "have the potential to support beneficial insect communities, such as pollinating bees, wasps, and predatory plant bugs." The invasiveness of the exotic ornamental species was not addressed in the study. Learn more at sciencedaily.com.

Climate Change May Benefit Native Oysters, But …
"Amid efforts to restore native oyster populations on the West Coast, how are oysters (Ostrea lurida) expected to fare under climate change in the decades and centuries to come? Not too badly, according to a study, but there’s a big “if” involved." Two species of introduced oyster drills (Urosalpinx cinerea and Ocinebrellus inornatus), which attack the oysters, may also increase in numbers due to warming. Learn more at sciencedaily.com.

Climate Change, Species Invasions Harming Popular Native Fish In Ontario Lakes
As the climate warms, so do lakes, allowing fish that prefer warmer waters to invade. Such is the case with Ontario lakes, where a popular recreational and commercial fish - the native walleye (Sander vitreus) - is at risk of disappearing as the competitive, predatory smallmouth bass (Micropterus dolomieu) invades the lakes. Learn more at phys.org.

Deadly Cat Poop Causes Rift Among Animal Defenders in Hawaii
"Two wildlife issues have collided in Hawaii, pitting one group of animal defenders against another in an impassioned debate. The point of contention? Deadly cat poop and the feral felines (Felis catus) that produce it." Learn more at phys.org.


Removing Johnson grass, and girdling and pulling glossy privet (using tools purchased with funds awarded through our Small Grant program) at Walnut Creek Metropolitan Park, Austin, TX, on September 24, 2016.
 Walnut Creek 1  Walnut Creek 2  Walnut Creek 3

Removing glossy privet at Headwaters at Incarnate Word, San Antonio, TX, on October 26, 2016.
Headwaters eradication 1   Headwaters eradication 2

If you would like to highlight a successful invasive species project or nominate a special person to be highlighted in an upcoming iWire, please send the details to iwire@texasinvasives.org.

Sentinel Pest Network and Invaders of Texas Species Workshops

Invaders of Texas workshops train volunteers to become citizen scientists to detect and report invasive species. Workshops, which are free, include information on the Sentinel Pest Network, which serves to increase the awareness and early detection of the Emerald Ash Borer, Cactus Moth, Asian Longhorned Beetle, and other pests of regulatory significance.

Workshops are tailored to meet the interests of your volunteer group, and supplementary session examples include an introduction to the TX Invaders mobile application and the Eradicator Calculator, a feature on Texasinvasives.org designed to help organize and track volunteer-based eradication efforts.

Upcoming Workshops:

For more information or to register to attend a free workshop, please visit the Workshop Page.