Researchers discovered that a plant invasive in at least 48 countries across India, Australia, and parts of Africa could escalate the spread of malaria. The so-called famine weed (Parthenium hysterophorus) infests disturbed land, roadsides, pastures, and farmlands. It causes a loss of yield in crops and is toxic to both humans and livestock. The weed thrives in warmer climates, is a native of north-east Mexico, and is endemic in America.

The plant releases chemicals called terpene from their roots that have fragrances that attract malaria carrying mosquitos (Anopheles gambiae). The adult female mosquitoes feed on the weed for the sugars, which provide them with the vital energy required for flight, mating/reproduction, and acquiring a blood meal (required for developing eggs). Female adult mosquitoes that emerge from breeding sites contaminated with famine weed chemicals emerged sooner and tended to live longer (11-12 days), increasing the likelihood to transmit the malaria parasite. Researchers also found that pregnant (gravid) females preferred laying their eggs in water treated with a blend of terpenes extracted from the famine weed roots.

The weed can be removed by the root, but it spreads rapidly via small seeds, making it hard to control and keep up with. Herbicides are also effective, but specialists caution that increased use of chemicals could become hazardous to the environment. There are two biological control agents that are available for famine weed depending on environmental conditions and habitat that could help minimize spread: stem-boring weevil (Listronotus setosipennis) and the leaf-feeding beetle (Zygogramma bicolorata) Researchers are optimistic that they may be able to exploit the fragrances produced by the roots of the famine weed to develop trapping tools to better target egg laying female mosquitoes and further the efforts of disease surveillance and control.

Read the research: Milugo et al. 2021

Invasive mussels are a constant problem across many freshwater systems from the Great Lakes to the Gulf. Zebra and quagga mussels (Dreissena polymorpha and D. bugensis) first arrived in the Great Lakes about three decades ago after hitching a ride from Eastern Europe. Since then, there have been several removal methods initiated and education campaigns launched to inform the public of the dangers of these aquatic dwellers. Some control methods may work for a small number of adults found on a fixed structure, but larger populations are harder to manage, and spread in open waters is unpredictable. Chemicals and molluscicide can often be toxic to native mussels, many of which are threatened or endangered.

Scientists are now studying methods of genetic control. This would allow for targeted treatments in infested waters without the worry of affecting other organisms. The plan is to use RNAi or RNA interference to “turn off” a targeted gene. RNA can act as a translator, helping convert the information stored in a cell's DNA into proteins essential to the body's function. RNA interference would block this process. RNAi research has led to the treatment for rare genetic diseases in humans, and research which involved injecting double-stranded RNA in the nematode worm won scientists a Nobel Prize in 2006.

Using RNAi as a biocontrol with zebra mussels is in its early stages, having started this year, but researchers believe that with the help of the genome that was mapped out in 2019, they can target certain genes. Some potential target genes are those that allow mussels to spread and survive, produce shell formation, and produce the threads that attach the mussels to a surface. The researchers believe they could also target the genes that predict stress responses, such as temperature and toxin tolerance.

To introduce the RNAi to the mussels, researchers would engineer a food source like bacteria or algae. The food could then be distributed to the mussels in a similar fashion as that of molluscicide, which involves a frame and tarp system to pump the chemical or “food” underwater.

Other scientists are considering a different approach for quagga mussels: read more here.

Sea lampreys (Petromyzon marinus) are an invasive species that have been causing population control problems in native fish populations in the Great Lakes for decades. Thanks to barriers, traps, sterilization, and lampricides the problem is not as bad as it was; however, scientists are still looking for ways to keep lamprey numbers down.

This fish has no bones and no jaw, but feeds by latching onto another fish with its unique suction cup mouth. When a lamprey approaches a surface, its annular muscle contracts and the buccal funnel spreads over that surface. A tooth-studded oral disc conforms to that surface, creating a seal, an armed tongue then retracts into the oral passage and seals off the buccal funnel from the pharyngeal cavity. This forms a partial vacuum inside the cavity and a suction force is created, maintaining suction attachment. Once the tongue protracts, the vacuum pressure spreads into the buccal cavity forming a stronger suction. However, scientists were curious about the control and conservation of the suction patterns of the lamprey.

In a study at Michigan State University Department of Electrical and Computer Engineering, researchers constructed “smart” panels to measure the oral suction pressure. With the device, they were able to describe the suction dynamics of juvenile and adult sea lampreys at multiple locations within the mouth. They found the suction dynamics were uniform all the way around the mouth, but that the suction pressure varied. They also found suction was not consistent, but rather occurred in intermittent cycles. They also found suction pressure increased significantly when trying to remove the lamprey. They found that the torpidity of water did not seem to affect the suction dynamics or pressure.

Researchers believe knowing the characteristics of the lamprey’s suction could be useful in the development of devices that detect, record, or respond to the presence of sea lampreys at a time or place.

Read the research: Shi et al., 2021

The avian vampire fly (Philornis downsi) was accidentally introduced to the Floeana Island of the Galapagos in the 1960s. Since then, it has spread across the islands, causing an increase in mortality rates of land bird offspring. The larvae of the fly feeds on the blood and tissue of the nesting birds, especially feeding around the inside of the birds’ nostrils. Recent studies have shown how Darwin’s finches are dealing with the parasitic fly, and how these behaviors may be pivotal for further insights into evolutionary pathways of introduced parasites.

One study, Common et al., 2021, examined which of Darwin’s finches seems to be the most successful host to the avian vampire fly. The parasite seemed to be the most abundant in the nests of the endangered medium tree finch (Camarhynchus pauper) and the least abundant in the nests of the hybrid tree finches (Camarhynchus spp.). Since the arrival of the vampire fly, medium tree finches have started interbreeding with small tree finches, forming hybrid populations. Researchers believe that this hybridization may be a defense strategy against the parasites since they see a much lower number of parasites in the nests of hybrids. There was also a low abundance of parasite activity in the nests of small tree (Camarhynchus parvulus) and small ground finches (Geospiza fuliginosa). These findings lead researchers to believe avian vampire fly survival across different hosts could evolve toward host specialization.

A second study, Katsis et al., 2021, examined how small ground finches (Geospiza fuliginosa) coped with being infected with the avian vampire flies. Researchers found that nestlings exposed to parasites had larger nares (nostrils), and that older nestlings exhibited a lower body mass. They also analyzed behavior to predict the severity of naris deformation. The researchers did this by handling the nestlings. When faced with high parasite infestations, more responsive nestlings had larger, more deformed nares compared to the more docile nestlings. These findings suggest the more responsive nestlings suffer greater fitness costs due to the parasitism. The researchers believe that one reason for this could be that more “vigorous” nestlings are attracting parasite larvae. They believe they may start to see the survival rate of docile nestlings increase, resulting in more surviving to adulthood- potentially changing the behavioral traits of small ground finches at a population level.

Are You Eating My Crops? 4 of 12

The sunn pest (Eurygaster integriceps) is one of the most devastation pests of wheat in the Middle East, and is the fourth headliner in our 12-month series called ‘Are you eating my crops?’. Individual pests chosen for this series have not yet been reported in Texas, but are on the ‘Watch List’ due to their high level of pest importance or risk due to host availability. During this series we will cover several different crop pests, what to look for, what they look like, and where you can find more information about them. If you ever have question or concerns regarding the headliners of this section, feel free to email invasives@shsu.edu.

The sunn pest, sometimes called the cereal bug or wheat shield bug, is a semi-elongated oval shaped bug, about 10-12mm long and 6.1- 7.1 mm wide, with a shield shaped pronotum. The upper surface is slightly concave with a large scutellum that covers almost the entire abdomen. The coloration is highly variable and has no taxonomic value, ranging from gray to creamy brown, to reddish or black. The sunn pest has five instars or nymph stages that are all spherical in shape, but variable in size. The first instar is small, 1.5mm in diameter, and light in color. It becomes black as the exoskeleton hardens. Nymphs are colored similarly to the adults except with 2-3 paired black dots midway between the lateral margin and midline of the abdomen. The eggs are spherical and about 1mm in diameter. They start out as a light green color and nearly translucent, but become dark as the embryo develops, eventually becoming pink with an orange, anchor-shaped mark.

One generation occurs per year. Inactive adults spend the winter and summer months in leaf litter and dense low growing vegetation. The lifecycle begins when overwintering females migrate small grain fields to feed and oviposit. Eggs hatch during the spring and first instar nymphs remain clustered around the eggs. Once the second instar emerge, the nymphs become more active, feeding on the leaves of the plant. Young adults will feed on the developing host plant until they are ready for migration and hibernation.

Wheat is damaged most by the sunn pest, but barley and other cereal and small grains are known to be damaged by pest activity. Nymphs prefer to feed on young leaves, while adults prefer to feed on kernels and ears, which stunts growth and plant development. Damage can be at its worst when overwintering adults feet on young wheat plants. In some areas, crop loss can be as much as 25-100% depending on the severity of the outbreak and if there is an absence of control measures. Chemical control is difficult and not environmentally sustainable.

Wheat is one of the most important crops in the U.S. and sunn pest would be detrimental agriculturally and economically if this pest becomes established in the U.S. To read more about the sunn pest, see the USDA fact sheet.

On July 7, 2021, Customs and Border Protection agriculture specialists at the Pharr cargo facility, Pharr, Texas, conducted an inspection on a commercial shipment of fresh vegetables arriving from Mexico. While inspecting a box of jackfruit, a live pest was discovered. The pest was submitted for identification to a U.S. Department of Agriculture entomology laboratory and was later confirmed as Cyclocephala forcipulata, a scarab beetle found Mexico. If accidently introduced, scarab pests can cause agricultural and economic damage as their larvae eat plant roots and adults feed on the aerial parts of plants. This is the first time this pest has ever been discovered at any of the nation’s posts of entry. The shipment was refused entry and returned to Mexico.

Read the press release.

WLS is a one-day FREE gardening event featuring live music, children’s activities, hands-on demonstrations, and top-quality presentations. WLS provides a venue for local gardening experts to share tips and tools to help residential landscapes of any size and shape become more water-wise and earth-friendly. Attendees can purchase native plants, compost bins, rain barrels and more.

Saturday, September 25, 2021
9 a.m. - Noon
The Recreation Center at Rob Fleming Park, Woodlands, Texas

**TexasInvasive.org will be hosting an education booth at the event. Our booth will feature ways to identify and remove invasive plants in your area, and discuss how to reduce invasive slug and flatworm populations that can harm your yard. We hope to see you there!

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 2020 Webinar Schedule:

• September 15, 1pm- Flowering Rush Biology, Management, and Control. REGISTER.
• October 20, 1pm- Forestry BMPs for Invasive Species. REGISTER.
• November 17, 1pm- USGS and USFWS collaborative project to conduct a national horizon scan for organisms in trade. REGISTER.

The 2021 Invasive Species Research Conference will take place virtually in an online event portal. Learn about current and published research from over 40 presenters in a variety of themed sessions. The event will also facilitate connections between invasive species researchers and practitioners in the Pacific Northwest.

October 5-7, 2021

Click here for more information or to register.

Invasive Spotlight:

Hydrilla
(Hydrilla verticillata)

Hydrilla is an aquatic perennial plant that grows submersed underwater. It is considered one of the world's worst invasive plants. It can quickly form dense underwater stands that raise water pH and temperature, and lower dissolved oxygen, which can affect populations of fish and other organisms. The dense mats provide a perfect mosquito habitat. It can make it difficult to boat, fish, and swim, and can potentially clog dams and water intake systems. Typically, rooted hydrilla have slender ascending branched stems up to 9 m (30 ft) long. Its leaves are small and pointed, 2-4 mm (0.1-0.2 in) wide and 6-20 mm (0.2-0.8 in) long, arranged in whorls of 4-8 leaves, bearing visible serrated teeth along the margins. Usually 1-4 small conical red bumps, or teeth, are evident along the underside midrib. It is easy to confuse hydrilla with native elodea (Elodea canadensis) and non-native Brazilian waterweed (Egeria densa). However, neither has bumps or sharp teeth along the leaf’s underside midrib. Elodea leaf margins are smooth and waterweed leaves are longer, 2-3 cm (0.8-1.2 in) long, with minute teeth on the underside midrib.

Interestingly, hydrilla plants exists as both monoecious and dioecious. Monoecious is when one produces separate “male” and “female” flowers on the same plant, and dioecious is when each plant produces only either “male” or “female” flowers. Only the dioecious type grows in Texas, and because it produces only “female” flowers, it cannot reproduce by seed. The whitish or translucent 3-petaled-&-3-sepaled flowers are tiny, 15-30 mm (0.0625-0.125 in) in diameter, and float on threadlike stalks that are up to 10 cm (4 in) long.

Fleshy buds called turions often form at leaf axils. They look like pinecones and grow up to 5 cm (2 in) long. Hydrilla also forms tubers among its roots. No other submersed species produces these structures. Both turions and tubers, along with stem fragments, act as dispersal units that can grow into new individuals.

Hydrilla is on the federal and TDA noxious weed lists, and TPWD regulated invasive plant list, yet it continues to be sold through aquarium supply dealers and over the internet. It is found in lakes, rivers, reservoirs, ponds, and ditches. It can cover hundreds of acres if left unchecked. Hydrilla is now found across the eastern US from Texas to Maine and is especially widespread in coastal states. Hydrilla is also found in several western states. The USGS Nonindigenous Aquatic Species database point map allows you to see the distributions of both.

If you believe you have identified a suspected hydrilla, please take a picture and REPORT IT! to invasives@shsu.edu.

Opportunities To Get Involved
Looking for participants for the following surveys: 

Citrus Greening Workshops

We need your help to safeguard Texas Citrus, and it can start in your backyard!

TISI is offering educational workshops focused on the Asian citrus psyllid and the pathogen Citrus Greening. The Asian citrus psyllid and the Citrus Greening pathogen is threatening citrus in multiple Texas counties, and we need your help to monitor the spread. The workshop will highlight what you need to look out for, address USDA-APHIS Citrus Quarantines, and offer diagnostic services if you suspect your backyard citrus has either the psyllid pest or Citrus Greening pathogen. This includes providing trapping materials, assisting with management strategies, and more.

Please contact invasives@shsu.edu so we can schedule a workshop (virtual or in-person) for you or your group this year!

Aquarium Watch: Looking for Prohibited Invasive Aquatic Species

Please help texasinvasives.org and natural habitats by looking for 14 prohibited invasive aquatic species being sold in your local aquarium store. With just one photo you can assist us in finding and documenting which stores are selling prohibited species. Texasinvasives.org will contact the appropriate Texas institutions to remove the species for sale.

If you would like more information please email invasives@shsu.edu, and mention you want to assist with our Aquarium Watch.

Weed out invasive annual grasses to keep Texas looking like Texas
The introduction and invasion of Mediterranean annual grasses are pushing out natives and leaving grasslands with a low forage value. Is this becoming the new normal or is there a way to stop the spread of invasives and recover Texas grasslands? sanantonioreport.org

US Influence on Australia's Illegal Pet Trade
The transnational smuggling of live animals poses a threat to Australia's biodiversity, conservation, environmental biosecurity, animal welfare, and human health and wellbeing. Researchers suggest that the unregulated trade of exotic pets in the U.S and other Western Countries has a major influence on Australians' desire for illegal pets. phys.org

Invasive Plants Are Still for Sale as Garden Ornamentals, Research Shows
Ecologists show that 1,330 nurseries, garden centers and online retailers are still selling invasive plant species as ornamental garden plants. This includes 20 species that are illegal to grow or sell nationwide. sciencedaily.com

Survey Suggests Climate Change Has Reduced the Presence of Invasive Argentine Ants
Decades of invasive Argentine ant (Linepithema humile) data has yielded surprising results, suggesting that the distribution has receded, and that climate change was a significant factor on the change. phys.org

In Fight Against Invasive Carp, Scientists Explore New Frontier: Track the Babies
Scientists at the U.S. Geological Survey and the University of Missouri are studying the complex way invasive carp eggs move in rivers, in hopes they can kill them while still young. phys.org

In the Absence of Genetic Variation, Asexual Invasive Species Find New Methods of Adapting to Their Environment
New research has found that two types of weevils (Naupactus cervinus and N. leucoloma), invasive in many parts of the world, have been using epigenetic changes to adapt and respond to different toxins in the plants they eat. The findings have implications for how we consider asexual invaders and how successful they can be. sciencedaily.com

Tool Predicts Which Native Fish Species Are Most at Risk from Lionfish Predators
Due to the growing concern regarding the spread of invasive lionfish (Pterois folitans) populations, researchers have created a tool to predict which fish are in the most danger of decline if, or when, the invasive predators arrive in their waters. phys.org

Raccoon dogs pose a particular threat to ground-nesting birds in Northern Europe
Artificial nest experiments demonstrated that the raccoon dog (Nyctereutes procyonoides), an alien species abundant in Finland, is a common duck nest predator. Racoon dogs laid waste to nests on shorelines, forests, rural landscapes, and urban areas. sciencedaily.com

How the African House Gecko Made Its Way to the New World
Researchers have found evidence that the African house gecko (Hemidactylus mabouia), now considered an invasive species, made its way to the New Worlds hundreds of years ago, aboard slave trading ships. phys.org

Invasive Cane Toads Found to Use Cannibalism to Improve Their Chances of Survival in New Areas
A team of researchers at the University of Sydney, Australia has found that invasive cane toad (Rhinella marina) tadpoles have given their species an advantage by eating the hatchlings of native toads. phys.org

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.
 

Citizen Scientists Spotlight

Citizen Scientists In The Galapagos

Citizen Scientists have rallied again. Seventy-four Galapagos residents were hired and trained to sample the genetic diversity across the small island chain. This is the first science project in the Galapagos to incorporate its citizens! The Barcode Galapagos Project uses local people to gather, prepare, and process samples in DNA sequencing machines set up in three laboratories on the island. They are making a genetic catalog of the biodiversity of the Galapagos and quantifying the variation of each species based on its geographical isolation. Citizen Scientists search the soil and the water for samples of island plant and animal life, big and small, to determine short DNA sequences of thousands of species that can be compared to similar species all over the world. The Charles Darwin Scientific Station has registered 10.659 species, both endemic and introduced, including mammals, bonefish, snakes, fungi, plants, plankton, and bacteria. Researchers say that 30-40% of the species they have sampled so far do not match any of those in a global gene bank. The project is scheduled to end in November 2021, but by then the hope is to have a full catalog of the islands information to help identify new species, fight illegal trafficking and fight invasive species.

The project involves researchers from Ecuador's University of San Francisco; the University of Exeter in England, the University of North Carolina at Chapel Hill and the Galapagos Science Center. Funding has come from U.K. Research and Innovation through the Global Challenges Research Fund and the Newton Fund.

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.

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