September 2016
Imported Red Fire Ants Can Have Complex Ecological Effects

Researchers at Texas A&M University studied the effects of the red imported fire ant (Solenopsis invicta) on small mammal populations, tick loads and pathogen presence in southeast Texas by reducing the ant population in treatment plots and comparing the results to those from untreated plots. They found that their index of small mammal population size was almost two times larger on the treated plots than the control plots. Tick load on hispid cotton rats (Sigmodon hispidus) was no different in the treated plots compared to the control plots, but for the fulvous harvest mouse (Reithrodontomys fulvescens) it was 27 times higher in the treated plots. Drag sampling for ticks uncovered no difference between the treatment and control plots. Seven Ambylomma maculatum ticks were infected with the human pathogen Rickettsia parkeri, although the proportion of ticks infected with R. parkeri was not different between treatment and control plots. These results confirm those of other studies that show that the red fire ant has a negative impact on small mammal populations, and also demonstrate that for at least one species of small mammal, the ants provide a benefit by reducing its tick loads. Additionally, fewer small mammals with fewer ticks in the presence of red fire ants also means that the likelihood of the transmission of tick-borne diseases decreases in the presence of red fire ants. For more information, read the research article.


Credit: USDA APHIS PPQ Archive

cotton rat

Hispid Cotton Rat (Sigmodon hispidus)
Credit: James Gathany, Centers for Disease Control and Prevention

Using Soil Bacteria to Control Cheatgrass

Cheatgrass (Bromus tectorum) is a highly invasive plant that has taken over much of the western U.S. and several other states. This annual outcompetes native plants for water and nutrients and alters fire regimes to the detriment of native plants. In sagebrush areas it threatens the sage grouse and the pygmy rabbit, both threatened by habitat loss. Cheatgrass is typically controlled with herbicide, but it is not very effective, partly because it needs to be applied year after year. Now, a scientist in Washington State who studies soil microbes has discovered a soil bacterium that is helping to control cheatgrass. Dr. Ann Kennedy found that a particular native species of bacterium inhibits the growth of the grass' roots, giving native plants the chance they need to survive and outcompete the cheatgrass. Unlike with herbicides, the bacteria remain in the soil for several years, and are not harmful to the native plants. The method does take a re-orientation of one's view of "control", however, because it takes several years for the cheatgrass to die out as the natives replace them. The researchers see a 50% reduction in cheatgrass after three years. This article provides additional information on this intriguing project.


Cheatgrass. Credit: Gary A. Monroe, hosted by the USDA-NRCS PLANTS Database


Cheatgrass. Credit: Chris Evans, University of Illinois,

Pull Invasives for Bats 

As part of Bat Conservation International's Bat Week, October 24 - 31, events are scheduled across the country to remove invasive plants. Removing invasives can improve habitat for bats by increasing native plant diversity and thereby increasing the diversity of insects available for bats. 

We encourage you to participate. Go to the event scheduler to look for events near you. If there is not an event near you, feel free to organize your own and add it to the list! Your neighborhood bats will thank you!

Ballast Water Treatment Treaty to Come into Force in 2017

Texas is home to a large and important shipping industry. Its ports receive hundreds of ships from around the world. Many of these ships carry ballast water that may contain invasive species. This worrisome fact is made even more so by the arrival of the much larger ships that can travel through the enlarged Panama Canal (the "New Panamax" ships). Not only will these ships be carrying larger ballast loads, they will also be arriving from ports in Asia that had previously only been shipping to U.S. ports on the Pacific Coast, potentially carrying more and new invasive species to Texas ports. However, there is good news on the horizon. On September 8, 2017, the International Maritime Organization's Convention on the Control and Management of Ships' Ballast Water and Sediments will enter into force. Adopted 12 years ago, it has finally been ratified by enough countries to allow it to enter into force.

The Convention will require all ships to take steps to reduce the likelihood that their ballast water carries invasive species. Its guidelines are intended to minimize the uptake of sediment and organisms, require at least 95% of the ballast water be exchanged a minimum of 200 nautical miles from shore, and require that ballast water be treated using acceptable means to sterilize the water.

While not all shipping countries have ratified the treaty, it is still an important step forward in controlling the spread of invasive species.

Read more at and at

ballast cycle


international maritime organization logo
Invasive Spotlight:
Chinese Tallow Tree
(Triadica sebifera)

The Chinese tallow tree is a deciduous tree that grows to 60 feet (18 m) in height and 3 feet (90 cm) in diameter. With its ability to begin reproducing after as little as three years; produce large numbers of seeds that are transported by both water and birds; change soil conditions that suppress the growth of other plants; tolerate shade, flood and saline soils; sprout from roots; and build a substantial seed bank, this highly invasive species can transform native habitats into monoculture tallow forests. It invades stream banks, riverbanks, and wet areas like ditches, as well as upland sites. The Chinese tallow tree is listed on the Texas Department of Agriculture's noxious weed list. It is an important invasive species especially in East Texas.

Its leaves are ovalish to rhomboid in shape, typically with a tip that is pinched into a point. Leaves turn a fiery red in autumn. Dangling yellowish flower spikes in spring yield small clusters of three-lobed fruit that split to reveal popcorn-like seeds in fall and winter.

Follow this link to learn more about the Chinese tallow tree.

Chances tallow tree with fruit

Credit: Chris Evans
Source: The University of Georgia,

TRSE6 autumn 2    Chinese tallow tree fruit

Left: Cheryl McCormick, University of Florida, Right: James H. Miller, USDA Forest Service,

More News

Restoring Guadalupe Bass After the Smallmouth Invasion
The Guadalupe bass (Micropterus treculii) is the Texas State Fish, yet it almost went extinct. One of the major contributors to its decimation was the introduction of smallmouth bass (M. dolomieu) into its rivers in the Hill Country, the only place it's found. However, the fish is on the rebound, thanks to a program to restock the Guadalupe bass in Johnson Creek and the Blanco River. Interestingly, the 2011 drought played an important role. Learn more about the restoration efforts.

Invasive Crawfish Found in NW Minnesota Lake
Two red swamp crawfish (Procambarus clarkia), which are native to southeastern states, were recently found in Tilde Lake, northeast of Moorhead in northwestern Minnesota. The Minnesota Department of natural Resources thinks they may be aquarium or crawfish boil releases. It is illegal to import or possess them in Minnesota. Learn more from

Combatting Feral Hogs, "Texas Style"
Feral hogs (Sus scrofa) cause damage to landowners' property and to wildlife habitat, across the country including here in Texas. A short documentary shows the "innovative" methods Texans are using to combat feral hogs, including using explosives, helicopters and an AR-15 rifle. Learn more from The Daily Caller.

A Tale of Two Invasives
The waterways of Central Europe have seen the decline of many species of arthropods. The culprits appear to be a team of shrimp (Dikerogammarus villosus) and a fish, round gobies (Neogobius melanostomus), both introduced from the Black Sea region. Studies show that the killer shrimp force native gammarid amphipods from hiding places and out into the open water, where the round gobies eat them. Learn more from

Asian Jumping Worms Speed Soil Nutrient Loss in Wisconsin Forests
Asian jumping worms, Amynthas agrestis and A. tokioensis, can be added to the list of non-native earthworms now living in North America. Unlike other earthworms, the Asian jumping worms, first discovered in Wisconsin in 2013, feed in the leaf litter instead of deeper in the soil. They are so efficient at turning the leaf litter into soil nutrients that these nutrients leave the soil before plants can use them. Learn more from

Using Mud Daubers in Search for Invasive Spider
Researchers have discovered that black and yellow mud dauber wasps (Sceliphron caementarium) - also known as the "dirt dauber" – hunt the newly introduced Joro spider (Nephila clavata). The spider was found in northeastern Georgia in 2014 and using the mud daubers could help track its spread. Citizen scientists are being recruited to look for mud dauber nests, the contents of which can then be investigated for the presence of the Joro spider. Learn more from

Beetle a Potential Control Agent for Water Chestnut
Water chestnut (Trapa natans), a native to Europe, Asia and Africa, was introduced to North America in the 1870s. Since then, water chestnut has spread across the Northeast, into Canada and as far south as Virginia. It causes problems by forming floating mats of vegetation that make rivers and lakes impassable for boats and swimmers, and prevent light and oxygen from reaching plants and creatures below. A researcher at Cornell University has found that a leaf beetle (Galerucella birmanica) is likely to be an effective biological control agent. Learn more from

Environmental DNA Used to Detect Invasive Crayfish
Organisms leave traces of themselves in the environment, including cells with their DNA. Scientists have only recently begun using this environmental DNA, or eDNA, to identify the presence of organisms like amphibians and fish, and this technique is even used to detect possible zebra mussels (Dreissena polymorpha) in Texas lakes. A researcher and his colleagues analyzed eDNA to successfully detect the presence of the highly invasive rusty crayfish (Orconectes rusticusat) in a dozen Wisconsin lakes. This is another example of using eDNA to monitor hard-to-detect species to provide early warnings of newly arrived invasive species. Learn more from


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 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 designed to help organize and track volunteer-based eradication efforts.

Upcoming Workshops:

Saturday, October 15, 2016
Location: St. Michael's Catholic Church (Jasper, TX)
Contact: Sue Singletary

Saturday, October 22, 2016
Museum of Handmade Furniture (New Braunfels, TX)
Contact: Deedy Wright

Saturday, October 29, 2016
Location: Collins Academy (Jefferson, TX)
Contact: Stella Barrow
Register for this workshop through; search for Citizen Scientist Training, or contact Stella Barrow.

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