Dengue fever is a common tropical disease that affects millions of people every year. The yellow fever mosquito, or Aedes aegypti, is the primary vector of dengue virus (DENV), as well as several other human transmittable viruses. For decades, researchers have strived to develop different ways to reduce the risk of vector transmission from mosquitoes and humans.

In a recent study, researchers decided to target the vector mosquitos with a special bacterium, then release the “infected” mosquitoes into the population, thus bringing the fight to the microorganismal playing field. The bacterium chosen is called Wolbachia. It was noted that dengue is not contracted in all geographic areas where Aedes aegypti is present. For example, in North Queensland, Australia, dengue infection is unusual. Turns out this is because mosquito populations were found to carry Wolbachia, a natural occurring infection in many insect species. This bacterium itself is benign toward humans, but can block the transmission of DENV from one person to another. However, it was found that under very hot conditions, the density of certain strains of Wolbachia could decrease, making it harder to spread and decrease the efficiency of the viral blockers, despite the bacteria’s general stability at high temperatures.

With this knowledge, researchers went to work knowing it was important to find the right strain(s). They transferred a Wolbachia strain, called wAlbB, to bacteria-free Aedes aegypti specimens, then released them into a vector population. After several years of research, the results suggest that the mosquitoes introduced to certain strains of the Wolbachia bacterium could successfully self-spread through a population, so much so that almost all local Aedes aegypti had acquired the bacterial strain. The release of additional Wolbachia mosquitoes into dengue hotspots was approved. There was an overall reduction of dengue fever (62.4% in 20 releases sites) and there was an evident reduction of dengue as Wolbachia frequency increased (75.8% reduction estimated at 100% Wolbachia frequency). The results spur hope in areas prone to tropical disease. Researchers hope more dengue-prone areas will be approved for Wolbachia mosquito release.

Read the Article: Hoffmann et al., 2024

Mysterious Snail

Authorities warn that Chinese mystery snail (Cipangopaludina chinensis) could become another problematic gastropod. They are sold as popular aquarium pets and as their current “invasive” status suggests, they become problematic when populations are established in the wild. They are known to compete with native snails for food and habitat and are known to carry parasites transmittable to humans, such as the intestinal fluke Echinostoma cinetorchis.

Chinese mystery snail received their name because female do not lay eggs, but instead give birth to fully formed juveniles. This gives the appearance that snails ‘mysteriously appear’. The embryos develop inside the female and the young are born in shallow water. Females can produce up to 100 juveniles in a single brood (birthing). Each generation lives an average of 3-5 years. Chinese mystery snails are generally found in lakes, ponds, ditches, streams, rice-paddies, or slow-flowing/quite bodies of water with soft substrates, such as sand or mud. Populations prefer densely vegetated areas. These snails are prone to great population booms and busts. They can tolerate stagnant or polluted water, but cannot survive very low oxygen levels and usually die off during algae blooms when the water is warm. When this happens, dead snails are usually found washed up around the shoreline.

Mystery snails have been reported in multiple U.S. states, including Texas. It is important to note mystery snails are different from the other invasive snails commonly found in Texas, such as apple snails (Pomacea maculata) and giant African snails (Lissachatina fulica). They can be distinguished from one another by their shell color and shape.
As a basic reference: apple snails can grow up to 1.5 inches and have a rounded shell. The color varies, but they produce bubblegum pink egg sacks above the water line. The giant African snail has a very elongated shell that can measure between 2-8 inches. Chinese mystery snails can grow up to 1.5 inches and their shell has 6-7 whorls in a tight conical shape. For additional information, please see the links above.

The best course of management is prevention. Authorities would like to remind the public to refrain from dumping their aquariums and bait contents into any water source. It is also important to sanitize fishing and boating equipment before moving from one body of water to another. Live animals of any sort should never be released into the wild. Please report any invasive species snail sightings to invasives@shsu.edu.

Feral Pigs, Donkeys, and Deer. Oh My… They What?

If you are a resident in Texas, there is a high probability that you are aware of feral pigs (Sus scrofa). Either you have had a one-on-one encounter, you know somebody who knows somebody, you have seen evidence of their presence at a local park, or you read an article about them. Regardless, they all over Texas, the U.S., and many other places worldwide. They are known as one of the most troublesome invasive mammals due to the amount of property and agricultural damage they leave behind. There are many proposed methods of control and/or culling, some of which have become controversial due to the overall questionable efficacy/result (but that is for another article).

A recent study suggest that some large invasive mammals may not be as detrimental to the environment, or specifically on plant abundance and diversity, when compared to native species. The study specifically looked at mammalian herbivores that that weighed more than 99 pounds, with the feral pig high on the list of those observed. Large herbivores affect ecosystems by consuming low-nutrient vegetation and dispersing seeds/nutrients as they go, regardless of native/introduced status. The primary quandary surrounding the study was, “if nativeness is a real biological variable, then it must be measurable.”

Results found that there was no evidence that the “introduced” large mammals negatively impacted the abundance and diversity of plants, based on the meta-analysis. Results also presented no evidence to support that introduced mammalian herbivores were more likely to facilitate introduced plant species compared to native mammals. Instead, the data strongly supported that functional traits more likely shape an organism’s impact on the environment, rather than its degree of invasiveness vs. nativeness. For example, how selective vs general a mammal diet is would more strongly correlate to its effect on plant life. Feral pigs are dietary generalists, and despite being ‘invasive,” they have been known to double native plant diversity in an area after feeding by suppressing the dominant competitors.

This research reminds us that words have power. It’s important to understand the vocabulary used when dealing with native, non-native, and invasive organisms. The researchers follow up by recommending the use of more caution when reporting an introduced organism is ‘harmfully’ impacting the subsequent environment and remind us that it is easy to label something as ‘invasive’ just because ‘it does not belong’.

Read the Research: Lundgren et al., 2024

Don’t Mess With Texas Citrus

TISI is offering FREE diagnostic services if you suspect your citrus has either the psyllid pest or the Citrus Greening pathogen, or you would like your citrus plants to be part of our screening survey.

The Asian citrus psyllid (Diaphorina citri) and the Citrus Greening pathogen (Candidatus liberibacter asiaticus) are threatening citrus in multiple Texas counties. By taking samples and monitoring the spread, it is easier to ensure that you and your neighbors are not affected. This pest and pathogen are extremely detrimental to Texas citrus, both economically and agriculturally. The presence of either can greatly affect citrus yield.

If you are interested in having your citrus trees checked or being part of the survey, please contact invasives@shsu.edu. If you are located within 200 miles of our headquarters, we can collect samples and/or provide traps and monitoring services. Otherwise, we will send you easy step-by-step instructions so you can do it yourself. Not only will we share the results and management strategies (where applicable), but you will become part of a multi-county monitoring survey that is striving to improve the health of Texas citrus!

Also Available: TISI offers educational workshops that highlight information about the Asian citrus psyllid, the pathogen Citrus Greening, and what you need to look out for in your own backyard. If you are interested in this, TISI will provide trapping materials, assist with management strategies, and more. Don’t waste another second.
Help us stop the spread!

This 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 2024 Webinar Schedule:

• April 17, 1pm CST- Field mapping protocols- What to consider when mapping for invasive plant species. REGISTER.
• May 15, 1pm CST- Invasive Lionfish. REGISTER.
• July 17, 1pm CST- Chondria tumulosa impacts to coral reefs in Hawaii. REGISTER.

We congratulate the Texas Gulf Coast Cooperative Weed Management program (CWMA) on another rousing success after their annual Fall Workday held on February 22nd, 2024. CWMA partnered with the Whooping Crane Festival and the City of Port Aransas Nature Preserve for a tree planting event. In 2 hours, 35 volunteers and CWMA members planted 66 native Texas trees, shrubs, and plants to restore wildlife habitat at Joan and Scott Holt Paradise Pond, Port Aransas. The collection of plants included 22 45-gallon trees, 8 30-gallon shrubs, 25 5-gallon shrubs, and 11 4-inch perennials.

If you know of any groups, orgs, or citizen scientists participating in invasive species or environmental efforts and would like to share their story, please contact invasives@shsu.edu.

The designation of the International Amistad Reservoir in the Rio Grande basin has been raised from “positive” to “infested” with invasive zebra mussels, signifying that an established reproductive population is present in the lake. The Amistad Reservoir is located along the Texas-Mexico border near Del Rio. Zebra mussel larvae was first detected in a water sample taken in early 2022, and again in later 2023, in an additional four water samples. In early 2024, adult mussels were found on previously submerged rocks exposed by low water levels. Read the full press release here.

TPWD emphasized how important it is for boaters, marina operators, and the general public to Clean, Drain and Dry all boats and water craft equipment before moving them, and to remain vigilant to stop the spread of aquatic hitchhikers. If you believe you have seen a zebra or quagga mussels, please take a picture and REPORT IT!

Invasive Spotlight:

Russian Wheat Aphid 
(Diuraphis noxia)

Russian wheat aphids (Diuraphis noxia) are small, lime-green insects with a distinct football-shaped body. They grow to be approximately 1.6-2.1 mm in length and many of their morphological characteristics require a hand lens or microscope to see. Sometimes the body is covered in a powdery coating of wax, giving them a pale appearance. The legs, antennae, and cornicles (a pair of back-ward pointed tubes on the dorsal side of the lower abdomen) are short compared to other aphids. They can be distinguished from other aphids by a second tail-like structure located on the abdomen called a supracaudal. When viewed from the side it gives them the appearance of having a double tail. This structure can be very difficult to see on smaller Russian wheat aphids and on winged forms, but can be more easily viewed on non-winged forms.

Russian wheat aphids, like most aphids, predominantly reproduce asexually. Aphids are female and each gives birth to live daughters that carry embryonic granddaughters. This allows them to produce multiple generations rapidly, which is the key to the explosive population growth achieved by many aphid species. When deemed suitable for the colony, males and oviparous (sexual) females will ‘appear’ so sexual reproduction can occur, and fertilized eggs can be produced. Aphid nymphs are sedentary and gregarious on the host plant, forming dense colonies. As the colonies increase in number, the aphids benefit as a group, causing them to develop and reproduce at a higher and higher rate. In their native range of Asia, the Russian wheat aphid also produce through sexual generation when a mated females lays eggs that overwinter. No males have been found in North America and it is believed that this species only reproduced asexually in the U.S. This inability to produce overwintering eggs may limit the northern range of the Russian wheat aphid in North America because it is more cold tolerant than greenbugs.

Russian wheat aphids feed on a variety of natural grasses and crop grasses, primarily wheat, barley, and rye. The Russian wheat aphid infestation causes leaves to curl up and remain longitudinally ridged. These straw-like enclosures areas provide a protected space for highly dense colonies to form, protected from temperature, predators, parasites, and chemical insecticides. Russian wheat aphid feeding causes purple or white longitudinal streaking on the leaves. It is not a known vector of wheat disease.

Russian wheat aphids are often mistaken for greenbugs (Schizaphis graminum), which are similar in color and size. The following differences can be used to distinguish these aphid species apart. Greenbugs long antennae and cornicles are often longer than the body, and they have a dark green stripe. Russian wheat aphids prefer to feed in rolled leaves on the upper parts of plants. Greenbugs are typically found on the undersides of lower leaves, but do not cause leaf to roll. Leaves damaged by greenbugs turn brown and appear scorched.

This invasive aphid pest has been reported in the Texas Panhandle and west Texas. When searching for the Russian wheat aphid, it is often useful to look for damage first, and then look for the aphids. For more information about Russian wheat aphid, see the TexasInvasives.org information page. If you believe you have seen Russian wheat aphids or evidence of their presence, please take a picture and report the location to invasives@shsu.edu. We will review your report and get back to you as swiftly as possible. Citizen Scientists are often our first line of defense. We appreciate your diligence and dedication.

General Note About Aphids: Aphids are phytophagous (plant feeding) insects that pierce the plant and sucks out the phloem. In most cases, aphids cause little to no damage to the health of the plant and their excrement, aka honeydew, is utilized by other insects and can be very beneficial. The honeydew can even attract secondary pollinators. It is not always necessary to intervene or spray chemicals when aphids are discovered. However, when an infestation occurs, they are known to cause leaves to curl, turn yellow, and/or stunt growth. If this happens on your garden plants, typically the application of Neem oil or Insecticidal soap can remedy the problem in place of harmful chemicals. If the aphid infestation present is found to be an invasive species, please see the appropriate management suggestions.

Get Involved Today!!

The Texas Invasive Species Institute (TISI) and The Texas Research Institute for Environmental Studies (TRIES) have many surveys and projects underway. These facilities strive to provide yearly invasive species presence and absence data to the authorities. Pre-screening is one of the first lines of defense in the war against invasives. However, sometimes it is hard to do it alone.

With the aid of the public and citizen scientists, we could cover a much wider area, and gather a more substantial amount of data. When it comes to protecting our environment, there is an opportunity for everyone! Together we can make a difference, one research project at a time.

See how you can get involved by reading the projects listed below or see all the available projects on the Texas Invasives website HERE.
 

These Aggressive, Venomous Fish Are Taking Over the Gulf of Mexico
TPWD would like to remind the public about the dangers of dumping aquarium pets, such as lionfish (Pterois volitans). While they are pretty, this invasive fish is aggressive, venomous, and has no natural predators in the Gulf of Mexico. khou.com

How Ants Are Breaking Down Biogeographic Boundaries and Homogenizing Biodiversity
Ants that have been transported by humans out of their native zones reshape ant communities. However, it seems that the human impact on biodiversity is overriding the biogeographical patterns that have resulted from millions of years of evolution. phys.org

How To Get Rid of Bastard Cabbage And Other Invasive Plants
Bastard cabbage (Rapistrum rugosum) is an invasive plant that poses a threat to many native plants, including our Texas blue bonnets (Lupinus texensis). They grow in collections of small yellow flowers and are often mistaken for Texas wildflowers. kvue.com

Bradford Pear Trees Look Pretty but Smell Like Rotten Fish. Should Texas Ban Them?
Bradford pear trees, also known as callery pears (Pyrus calleryana) are listed as an invasive species in Texas. So why do people keep planting them? statesman.com

How Climate Change Drives the Spread of Invasive Plants
As the climate warms, the number of invasive species around the world are expected to increase 36% by 2050. Climate change is altering the environment to favor invasives, which is causing biodiversity loss. phys.org

Invasive Plant Time Bombs: A Hidden Ecological Threat
A new study has found invasive plants can stay dormant for decades or longer before rapidly expanding and wreaking ecological havoc. sciencedaily.com

Yellowstone Seeks to Stiffen Invasive Species Rules, Ban Some Boats
Keeping the major rivers in Yellowstone free of invasive species is an important task. To do this the park is looking to enforce additional restrictions, such as a 30-day “dry time” and a one strike ban policy. wyomingnews.com

Invasive Pacific Oyster Proliferation During Blob Marine Heat Wave Portends Similar Events as Seas Warm
During the Washington Pacific Blob heat wave, there was a rise in sea temperatures. A recent study examined how the heat wave effected the wild Pacific oyster populations. phys.org

Invasive Beetle Species Found in Central Valley
A new invasive species of beetle, called almond beetle (Carpophilus truncates) was recently found infesting almonds and pistachios in the San Joaquin Valley, California. theriverbanksnews.com

A Crown Rust Fungus Could Help Manage Two Highly Invasive Plants in Minnesota
Invasive crown rust (Puccinia coronata var. coronate) was recently found it could be beneficial in managing glossy buckthorn (Frangula alnus) and reed canarygrass (Phalaris arundinacea), two highly invasive wetland plants. phys.org

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, teach identification of local invasive plants, and 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.