November 2017
Giant Salvinia and Zebra Mussels Extend Their Range

October and November were busy months for the Texas Parks and Wildlife Department (TPWD): its biologists have confirmed that both invasive giant salvinia (Salvinia molesta) and zebra mussels (Dreissena polymorpha) have extended their ranges.

Giant salvinia was confirmed at three locations on Lake Fork – the largest total infestation ever found on the lake – Oct. 26, within hours of being notified by a local property owner (and illustrating the importance of people keeping an eye peeled). A containment boom was placed to isolate the worst-affected cove. However, because it is "scattered throughout the lake,... eradication would be almost impossible at this point." If you find it, please report it!

For more information, see the TPWD news release.

Meanwhile, TPWD biologists have classified Lake Georgetown as "infested" with an established, reproducing population of zebra mussels and have also changed the status of Lake Livingston to "infested". This was soon after Richland-Chambers Reservoir was classified as "positive", as we reported in last month's "iWire".

Routine water sampling in Lake Georgetown found larvae, and a follow-up survey Nov. 6 revealed young settled zebra mussels attached to rocks along the shoreline. This was surprising because no evidence of zebra mussels was found as recently as spring of this yerar. Brian Van Zee, TPWD inland fisheries regional director, said, “It just goes to show how rapidly zebra mussels can colonize and establish themselves in our lakes once they are introduced.”

Lake Livingston was previously classified as "positive" with multiple detections of zebra mussels. It has now been upgraded to the "infested" classification after ongoing research confirmed that zebra mussels have developed a reproducing population in the lake.

In 2017, four Texas reservoirs have become infested with zebra mussels, bringing the statewide total to 13 infested lakes.

For more information on the presence of zebra mussels in these two lakes, see the TPWD news release.

zebra mussel
Credit: Amy Benson, US Geological Survey,

Giant salvinia on Lake Fork.  Credit:

salvinia in hand
Credit: TPWD

Citizen Scientists of the Month

Speaking of giant salvinia, residents of Uncertain, Texas, have taken up the battle against the invasive species with the help of a small Brazilian insect known as the salvinia weevil (Cyrtobagous salviniae). By releasing these tiny soldiers onto the pervasive plant, they're hoping to save the lake and their home. Thank you, Greater Cado Lake Association of Texas, for your inspiring efforts!  See their great work described in this wonderful video by Great Big Story, and in this video.

GCLA releasing weevils
Greater Cado Lake Association members releasing salvinia weevil in Lake Cado.  Credit: Darren Braun, Texas Monthly

Native Trees, Shrubs Provide More Food for Birds

Plant native trees and shrubs in your yard, and you can really help songbirds. In a study of the Carolina chickadee (Poecile carolinensis) in the metropolitan DC area, researchers found that native trees and shrubs support much more 'bird food' -- caterpillars -- than non-natives do. Over the course of her four-year study, doctoral student Desiree Narango looked at 203 yards. One thing that has stood out to her is the sheer number of different trees that are planted in these yards: over 375 species.

It became apparent quickly that while this high diversity may look like a good thing, some trees are better than others with regard to sustaining food webs. In particular, "native trees are better at providing caterpillars for birds," said Narango. There are a lot of non-native plants -- such as zelkova, ginkgo and lilac -- that don't provide any resources for breeding birds.

Narango also found that the number of caterpillar species a plant supports predicts how strongly chickadees prefer it. "When these birds would choose a tree, all the other birds in the neighborhood were choosing those trees, too… In a way, our chickadees were telling us what all of the birds want during that period," said Narango.

Learn more at

Carolina Chickadee

Carolina chickadee with caterpillar
Credit: Desiree Narango and Doug Tallamy, University of Delaware

New K-9 Initiative Could Transform Pest Surveys

It’s a potential game-changer for U.S. plant health protection: highly trained detector dogs that can find a specific invasive pest or disease in the field.

These detector dogs could accompany pest survey specialists during a foreign pest or disease outbreak, speeding the efforts of USDA’s Plant Protection and Quarantine (PPQ) program to determine the infestation’s boundaries and identify pest-free areas. They could also work at ports, sniffing entire shipments of commodities to detect traces of insect larvae or plant disease.

Read this article for more information.

See also this article at

PPQ dog sniffer

'Super Invader' Tree Hits South, But Flea Beetle May Be Hero

The tallow tree (Triadica sebifera), a "super invader" with toxic leaves and no natural enemies in North America, is conquering the South.

Overtaking forests from Texas to Florida, tallows grow three times faster than most native hardwoods, and each one casts off 100,000 seeds a year. U.S. Forest Service data show tallow now spreading across 10 states. Its growth nearly tripled in Texas in the last two decades, and increased 500 percent in Louisiana, where its higher tolerance for salinity enables it to crowd out moss-covered bald cypress (Taxodium distichum) in swamps and bayous. Populations also are up along the Atlantic coast, from Florida to the Carolinas.

Some scientists say introducing a flea beetle from the tallow's native habitat in eastern China may be the best alternative. The flea beetle (Bikasha collaris) generally ignores other plants as it eats the roots and leaves of the tallow, a host-specific tendency tested on about 150 other plant species in a decade of laboratory work in the U.S. and China, researchers said.

The USDA-APHIS has been working on an environmental impact assessment, which will include a public comment period. If approved, the bugs could be released sometime in 2018.

Read more. This article also includes a video.

Learn more on the biological control of Chinese tallow.

Chinese tallow tree
Linda Price, Invaders of Texas

flea beetle
Credit: Gregory Wheeler, USDA

APHIS Posts New Weed Risk Assessments

APHIS’ Plant Protection and Quarantine (PPQ) has posted Weed Risk Assessments (WRA) for the following two weed species:

While neither species is in Texas, the WRAs for both species conclude that they could grow in Texas, and that they have a high probability of becoming invasive. Please keep a lookout for them!

The purpose of a WRA is to evaluate the likelihood that a weed species will escape, naturalize, and spread in the United States, and harm U.S. natural and agricultural resources.

To view or print these or other assessments, visit APHIS’ Noxious Weeds Program Risk Assessments Web page.


Invasive Spotlight:
Gypsy Moth
(Lymantria dispar)

The gypsy moth (GM) consists of two subspecies, the Asian and the European. The European GM has established in the northeast United States, where it can cause extensive damage by defoliating trees over large areas when infestations are high; the Asian GM has not established in the U.S. Each GM female could lay egg masses that in turn could yield hundreds of voracious caterpillars with appetites for more than 500 species of trees and shrubs. Defoliation can severely weaken trees and shrubs, killing them or making them susceptible to diseases and other pests. Caterpillar silk strands, droppings, destroyed leaves, and dead moths are a nuisance in homes, yards, and parks.

Adult moths vary in appearance. Males are tan to brown with irregular black wing markings, feather-like antennae, and a wingspan of 37 to 50 mm. Females are usually larger, with a wingspan of up to 62 mm. They are whitish in color with faint darker, wavy bands across the wings. The female European gypsy moth is flightless, however the female Asian gypsy moth is a strong flier. Asian gypsy moths are significantly larger than the European gypsy moths.

GM caterpillars are hairy, about 2-3 mm long when newly hatched, and grow to about 60 mm long. They have two rows of large spots along the back, usually arranged in five pairs of blue and six pairs of red from head to rear.

GM infestations spread in several ways. Adult female moths may fly to previously uninfested areas to lay eggs. Or, newly hatched GM caterpillars may climb to tree crowns, where the wind picks up their silken thread and carries them to other areas. In addition, people can inadvertently transport egg masses. GM egg masses are tolerant of extremes in temperature and moisture and travel well on logs, lawn furniture, nursery stock, pallets, shipping containers, and on the hulls and riggings of ships.

Because of its potential negative impacts in Texas, the gypsy moth is a Report It! species as part of the Sentinel Pest Network, a component of If you believe you have found a gypsy moth, please report this species.

Follow this link for more information on the gypsy moth.

Dark = male, light = female.
Credit: John H. Ghent, USDA Forest Service

gypsy moth caterpillar
Credit: echoe69 (flickr) (CC license)

gypsy moths laying eggs
Females laying eggs.
Credit: James Tourtellotte, CBP,

More News

Economists Develop Decision-Making Method for Lionfish Management
The lionfish (Pterois volitans) has invaded the Texas coastal and offshore waters. Researchers used mathematical modeling to produce a decision-making framework that natural resource managers can use to properly account for the cost for targeted removal of lionfish from a priority area, such as a marine sanctuary, potentially helping to reduce management costs. Read more at

Poison-Ivy an Unlikely Hero in Warding Off Exotic Invaders?
The invasive Japanese knotweed (Fallopia japonica) causes much more severe damage to floodplain forests along the Susquehanna River, Pennsylvania, than previously thought. Furthermore, the researchers point to a key role for the often-maligned poison-ivy (Toxicodendron radicans) as a native species that can not only compete with knotweed but also help sustain the growth of new trees. Read more at

EU Trade Ban Brings Down Global Trade in Wild Birds by 90 Percent
Trade of wild birds has dropped 90 percent globally since EU banned bird imports in 2005. International trade of wild birds is a root cause of exotic birds spreading worldwide. Learn more at

Gene Drive Technologies for Ecosystem Conservation: Use with Care
Scientists working in the vanguard of new genetic technologies have issued a cautionary call to ensure that possible applications in conservation will only affect local populations. Researchers examined the possible consequences of the accidental spread of existing CRISPR self-propagating gene drive systems, such as the one proposed to control mosquitoes. Read more at

Invasive Frogs Give Invasive Birds a Boost in Hawaii
Puerto Rican coqui frogs (Eleutherodactylus coqui) were accidentally introduced to Hawaii in the 1980s, and today there are as many as 91,000 frogs per hectare in some locations. New research has found that native birds were unaffected, while some non-native birds were more abundant, in the presence of the frogs. Read more at

Healthy Marine Ecosystem Resists Invading Non-Native Algae
Research on kelp ecosystems off the California coast indicates that when healthy, they can resist invasion by the non-native algae Sargassum horneri. Learn more at


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

Sentinel Pest Network and Invaders of Texas 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 designed to help organize and track volunteer-based eradication efforts.

Upcoming Workshops:

Saturday, January 20, 2018
Location: Headwaters of the Incarnate Word (San Antonio, TX)
Contact: Pamela Ball

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