December 2020
Tegus on the move

Authorities have been monitoring and tracking the invasive Argentine black-and-white tegu (Salvator merianae) population in Central and Southern Florida for a decade. In May 2020, confirmed tegu reports placed the lizard in two counties in Georgia. Since then, the tegu has been found in four counties in South Carolina, with isolated reports in Alabama, Louisiana, and Texas. The invasive Argentine tegu is native to South America, has black and white mottling, grows up to 4 ft long, is docile, and an omnivore with a voracious and vast appetite. They eat anything from eggs, small animals, seeds, fruits, and vegetables. They will pluck eggs from ground nesting birds, endangered sea turtles, crocodiles, and alligators. Because of their insatiable appetite, they could become very problematic for farmers by stealing eggs from chicken coops, eating fruit/vegetable crops. Females lay about 35 eggs per year. During the winter, they go into a state of brumation (similar to hibernation). The south eastern U.S. is prime climate for them and has many areas of suitable habitat: grassland, woodland areas, and especially areas with substantial seasonal rain.

The Argentine tegu was first introduced to the U.S. via the exotic pet trade. Since then, individuals have been released into the wild by their owners, or have escaped. The tegu is very hardy, making spread difficult to control once a reproductive population is established. The USGS is currently conducting surveys and research to better understand tegu group dynamics so a more productive removal strategy can be developed. There are no official estimates of how many there are in the United States.

Authorities ask if you have a tegu or any other exotic pet, to please take the necessary precautions to prevent escape. If you are unable to care for or no longer want your exotic pet, please do not release it into the wild. Instead contact a Reptile Adoption group or local wildlife center. Tegu in particular are still desired as pets and in some areas there is a long waiting list of families that can provide a suitable home. 

Argentine black and white tegu (Salvator merianae)
Argentine black and white tegu (Salvator merianae). Credit: Florida Fish and Wildlife Conservation Commission.

USGS scientinst conducts radio telemetry on Argentine black-and-white tegus in the Florida Everglades.
USGS scientinst conducts radio telemetry on Argentine black-and-white tegus in the Florida Everglades. Credit:

Bye Bye Pink Bollworm

The pink bollworm (Pectinophora gossypiella) has been eradicated from the cotton-growing areas of the continental U.S. and northern Mexico after a multi-decade, multifaceted efforts, according to a recent publication by Agricultural Research Service (ARS) and University of Arizona (UofA) scientists, in the Proceedings of the National Academy of Sciences.

Pink bollworms were a major cotton pest in the southwestern U.S., especially in cotton-growing areas like Arizona, California, Texas, and New Mexico. The adult moths live a short two weeks, but a single female can lay 200 or more eggs. When the eggs hatch, the larvae will bore into the cotton bolls to eat the seeds. When the larvae mature, they cut their way out, drop to the ground, and cocoon near the soil surface. The boring, eating and cutting behavior can destroy the fibers of cotton, reducing quality and crop yield. As a result, there were as many as nine pesticides developed specifically for the control of pink bollworm.

In 1996, cotton was genetically engineered to produce proteins from the bacterium Bacillus thuringiensis (also called Bt cotton) because it kills pink bollworms and other cotton pests but is harmless to humans and beneficial insects. To reduce resistance, non-Bt cotton refuges were planted. Working with farmers, this strategy reduced the pink bollworm population by 90% in 10 years.

In 2006, based on analysis of computer simulations, and 21 years of field data from Arizona, it was proposed that Bt cotton and sterile insect releases would interact synergistically to reduce the pest’s population size. A multifaceted team was formed and soon billions of sterile pink bollworm moths were being dropped from planes onto fields in order to overwhelm field pest populations, and only Bt cotton was planted. In 2005, Arizona estimated its pink bollworm population to be 2 billion; by 2013, it was zero. This strategy saved Arizona alone over $190 million between 2014-2019, and reduced the use of insecticide by 82%. With complementary regional efforts, the pink bollworm was eradicated throughout the cotton-growing areas of the continental U.S. and northern Mexico. The research paper, mentioned above, concluded the eradication of this pest improved the overall environment, brought back beneficial insects, and that the ecology returned to a more natural balance.

Pink Bollworm. Illustration by Arthur Cushman
Pink bollworm (Pectinophora gossypiella). Illustration by Arthur Cushman.

pink bollworm (Pectinophora gossypiella) pink bollworm larvae (P. gossypiella)
Pink bollworm. Top: Adult. Bottom: Larvae. Credits: Top: Mississippi State University. Bottom: Todd Gilligan, CSU.

Texas State Renews Habitat Conservation Pact

A seven-year contract between Texas State University, the City of San Marcos and the Edwards Aquifer Authority (EAA) for habitat conservation was approved by The Texas State University System Board of Regents during its meeting earlier this month (12/12/2020). The contract is a renewal of the agreement originally established in 2012, which implemented the EAA Habitat Conservation Plan Program for the San Marcos River. The EAA Habitat Conservation Plan Program is required by the federal Endangered Species Act.

The contract stipulates four main objectives: removal of non-native plants, enhancement of Texas wild rice, removal of floating plants, and management of key recreation areas. In doing so, Texas State University will be reimbursed up to $2.8 million by the EAA through the city.

Habitat conservation plan and management of the Edwards Aquifer also includes and is subject to pumping restrictions during droughts, control of the spring headwaters and the river, restoration of the habitat for the endangered species, and removal of invasive species. Conservation efforts are reliant on contracts such as these, as well as permit holders and volunteers in order to maximize efforts.

  The Edwards Aquifer Region
 Edwards Aquifer Region. Credit:
North American Invasive Species Management Association Training Webinars

The program is designed to provide the education needed for professionals and students who are managing or learning to manage invasive species. The courses include the most current invasive species identification, control and management techniques, and how to comply with local and federal regulations.

Participants may register and enroll at any time and will receive a certificate of invasive species management from NAISMA upon completion of the program.

All live webinars are open to the public. Recorded webinars are available to members of NAISMA.

NAISMA 2020 Webinar Schedule:

  • New NAISMA webinars available in 2021


Invasive Spotlight:
Yellow Floating Heart
(Nymphoides peltatum)

Yellow floating heart is a freshwater floating perennial that grows in slow-moving water ways, such as lakes, ponds, swamps, channels, and even mudflats. It grows rapidly, covering the entire surface of the water, shading out and outcompeting native vegetation. Decomposing vegetation impacts water quality causing severe declines in algae, disrupting the entire food web. Thick mats can create stagnant, low- oxygen water conditions that create ideal conditions for mosquitos, but force fish to relocate, and make water recreation impossible.

Yellow floating heart possesses runners (stolons) that grow up to 2 meters, and aggressively root in the substrate. The round to heart-shaped leaves float and range from 1.2 - 5.9 inches in diameter (3 - 15 cm). They have slightly wavy margins, and usually grow in an opposite and unequal arrangement. Leaves are green to yellow-green and often purplish underneath. Flowers are bright yellow with five petals, each with fringed edges, and range in size from 1 - 1.5 inches (3 - 4 cm) in diameter. Two to five flowers grow from each node above the water surface on a stalk. The plant usually flowers between May and October.

Yellow floating heart was intentionally introduced in the U.S. as an ornamental plant in water gardens, and escaped captivity. It has since spread to numerous states both intentionally and accidently. It is spread naturally by producing daughter plants that break off and float to new areas, via rhizomes and tubers, and by hairy seeds that are spread by water currents or animals. Watercrafts also spread it by fragmenting and carrying it to new locations. Although this species is prohibited in some states, including Texas, it is widely available for purchase online. As a TPWD regulated species, it is illegal to sell, buy or transport yellow floating heart in Texas.

Yellow floating heart threaten aquatic habitats, especially in East Texas. Click here to learn about native look-alikes, management, and more. If you believe you have identified a suspected yellow floating heart, please REPORT IT! here.

If you are a private or public water property owner with exotic aquatic species that you wish to remove, you may now have new options for removal due to rule changes recently issued by TPWD. See TPWD adopted rule changes.

yellow floating heart
Yellow floating heart (Nymphoides peltatum), example of thick mat. Credit: Lyn Gettys, University of Florida.

yellow floating heart flowers
Bright yellow flowers with five petals. Credit: Mark Malchoff, Univ. of Connecticut.

yellow floating heart leaves
Round to heart-shaped floating leaves. Credit: Vick Ramey, University of Florida.


Website Changes: Coming 2021!!

As merges with Texas Invasive Species Institute (TISI) there will be some changes to the appearance and overall design of the monthly iWires and website. The newsletter will still be emailed and posted monthly, while continuing to report on the Texas invasive species news that you have all come to rely on and enjoy. The website will have an updated aesthetic, but will still be located at and will provide you all the Invasive Species reporting functions, workshops and resources you need to successfully report and manage invasive species.

There are many exciting changes to look forward too: streamlined “report it” function, virtual Citizen Scientists trainings and certifications, searchable database of invasive species information and a searchable iWire article database with a ‘related articles’ tag function. We will continue to alert you of changes until the site is fully launched.

TISI Home Screen JPG

Zebra Mussel Watch

TWPD has designated Lake Buchanan as “infested” with zebra mussels (Dreissena polymorpha) after a series of sampling efforts. Lake Buchanan is the second largest of the Highlands lakes, located west of Burnet and north of Inks Lake in the Colorado River Basin in Central Texas. Lower Colorado River Authority (LCRA) scientists discovered zebra mussel larvae in plankton samples taken from three sites around the lake in October, and at two of three sites taken around the lake in November, all samples were confirmed by TPWD. In December, settled zebra mussels were discovered around Buchanan Dam. Additional surveys for settled zebra mussels were conducted, but none were found. The current population appears to be small, but the presence of both larvae and adults found several months apart indicated an established, reproducing population of zebra mussels. Inks Lake, located downstream, is likely to become infested. TPWD is encouraging boaters and homeowners on Lake Buchanan and Inks Lake to keep an eye out for zebra mussels.

If you believe you have identified a suspected zebra mussel, please REPORT IT!

Park authorities remind everyone to Clean, Drain, and Dry their boat, trailer and gear to prevent spreading aquatic invasives from lake to lake. Here is how you can help Stop Aquatic Hitchhikers by appropriately cleaning your recreational gear.

mussel signal KNK
 Credit: Kylee N Kleiner, TRIES

More News

A New Study Shows How Invasive Species Change During Biological Invasion
Several scientific studies have shown how species introduced by humans in new places are different compared to those in their native areas. This was interpreted as an adaptation to the new place after introduction. However, a new study shows such differences occur before the introduction. This finding questions the interpretations of previous studies and opens the possibility of new management strategies to combat the negative impacts of invasive species.; Research paper.

Research Successfully Removes Invasive Quagga Mussels from Lake Michigan
Scientists reported reductions in cladophora algae and quagga mussel (Dreissena bugensis) density in Lake Michigan’s offshore waters near Sleeping Bear Dunes National Lakeshore after an underwater project by the Invasive Mussel Collaborative.

New Conservation Bill from Sen. Bennet Would Fund Wildfire Mitigation and River Clean-Ups, Create 2 Million Jobs
Colorado introduced the Outdoor Restoration Force Act that will fund a range of projects from wildfire mitigation to river clean-ups. The money would be split between state, local governments and federal efforts at the Departments of Agriculture and the Interior, as well as the Environmental Protection Agency. The fund could create and sustain 2 million jobs.

Another Invasive Lizard Species Has Landed in Florida: The Red-Headed Butterfly Eating, Agama Lizard
The red-headed Agama picticauda lizard (Agama agama) is new to South Florida. While not yet considered to be as serious of a threat to local species as the tegu or the Burmese python, scientists are still on their toes about their potential effects on Florida’s animal kingdom.

Invasive in the U.S., Lifesaver Down Under
New research reveals the yellow-Spotted monitor lizard (Varanus panoptes) and Gould's monitor lizard (V. gouldii) should be regarded as 'ecosystem engineers' as they provide food and shelter to other reptiles, insects and mammals, helping prevent extinction.; Research paper.

Invasive Harlequin Ladybird Causes Severe Decline of Two-Spotted Ladybird, New Study Shows
Scientists have led an 11-year study which shows how the invasive harlequin ladybird (Harmonia axyridis) caused the severe decline of the two-spotted ladybird (Adalia bipunctata) on broad-leaved trees and shrubs in northern Switzerland.

Study Examines Attitudes Toward Non-Native Birds
A new study from the Cornell Lab of Ornithology examines the public attitude towards non-native bird species, such as European Starlings (Sturnus vulgaris) and House Sparrows (Passer domesticus), and whether people are willing to manage them to protect native cavity-nesting birds. The study also highlights the importance of monitoring through citizen scientists.; Research paper.

International News

Scientists Took a Rare Chance to Prove We Can Quantify Biodiversity by 'Testing the Water'
An invasive species eradication program in the UK provided the ultimate case study to evaluate the success rate of eDNA sampling in identifying species abundance and biomass in natural aquatic habitats.; Research paper.

Miniature Guttural Toads on Mauritius And Reunion Stun Researchers
Researchers in South Africa have found that invasive guttural toads (Sclerophrys gutturalis) body size have reduced by up to one-third compared to their South Africa counterparts after 100 years after their introduction to the islands of Mauritius and Réunion.; Research paper.

Genetic Research Reveals the Origin, Diversity and Colonization History of the Invasive 'Tramp Slug'
Based on genetic variation, the origin, routes of colonization, and rate of spread of the invasive tramp slug (Deroceras invadens) has been investigated. Their results can be compared against historical records of when this species first turned up around the world.; Research paper.

Crab-22: How Norway's Fisheries Got Rich – But on An Invasive Species
When the fishermen of a Norwegian fishing village learned of the million-dollar Alaskan king crab fishery, they realized the crab could be more boom than bust. Today, the invasive red king crab (Paralithodes camtschaticus) is largely credited with rescuing the fishing villages, but at what cost.

Kerala’s ‘Pink Phenomenon’ Can Choke Water Bodies and Drains, Warn Scientists
The widespread growth of an aquatic plant called Red Cabomba (Cabomba Furcata) has painted the water bodies of a village in Kerala’s Kozhikode district pink. Hundreds have descended to the village in the middle of the novel coronavirus disease (COVID-19) pandemic to witness it.


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 detect and report invasive species as citizen scientists. Workshops, which are free, are designed to introduce participants to invasive species and the problems they cause, cover aspects of invasive species management, and teach identification of local invasive plants, and to train participants to report invasive plants using the TX Invaders mobile application. The workshop is 7 hours long (usually on a Saturday, but scheduling is arranged with each individual host group). The workshop satisfies Master Naturalist training requirements.

Sentinel Pest Network workshops serve to increase the awareness and early detection of a set of particularly important invasive species, to help prevent their spread into Texas or their further spread within Texas. Participants learn to identify species such as the Emerald Ash Borer, Cactus Moth, Asian Longhorned Beetle, and other pests of regulatory significance, and to report them. The workshop is 3.5 hours long. The workshop satisfies Master Naturalist training requirements.

Upcoming Workshops:

--None scheduled--

*Coming soon in 2021: Virtual Seminars and training!!*

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