April 2020
First Case of Apple Snails Damaging Rice Crop Reported in Louisiana

The apple snail (Pomacea maculata) is a major pest in rice fields in Asia. While it is found in coastal states from South Carolina to Texas, as well as in Arizona, it has not caused significant damage to rice crops – until now. The snail has destroyed a 50-acre field of rice in Louisiana. Louisiana State Univeristy AgCenter entomologist Blake Wilson said, “There was no trace of rice. If you didn’t know better, you’d think it was a snail production farm.” Two years ago the farmer's crawfish traps were clogged with snails, but no rice damage occurred.

Wilson said he wants to know why the snail population was so high in this field compared to nearby fields.

AgCenter rice specialist Dustin Harrell said apple snails have been a problem in Texas rice fields. “Most of it is from clogging drains and causing breaks in the levees,” he said. “This is the first time in North America with significant damage in a stand of rice."

The farmer plans to replant and control the snails with copper sulfate.

Read more at thenewsstar.com.

Credit: wwltv.com

More on the Great Conundrum of Pablo Escobar’s Hippos

Last month we reported on the hippos (Hippopotamus amphibius) that the Colombian drug kingpin Pablo Escobar introduced to Colombia. This opinion piece continues the discussion on the impacts that the research on those hippos and other large introduced herbivores is having on the thinking by conservationists about what state we are trying to protect. Are such species helping to "rewild" areas?

The author argues that because what we do in the name of restoration and conservation is actually human intervention, perhaps what we are doing is not "natural". And if not, then perhaps allowing certain invasives that restore aspects of ecological function to remain should not be dismissed. "As the crisis of biodiversity becomes more dire, it’s possible we’ll need to disrupt the planet further to save it." On the other hand, we would argue that if such species do more to improve an ecosystem than to harm it, then by definition they may no longer be considered "invasive" – only "non-native".


COVID-19 Pauses Green Crab Trapping in Washington

Concerns over COVID-19 are keeping resource managers and their volunteers across the Olympic Peninsula and Western Washington from continuing their work to manage the invasive European green crab (Carcinus maenas). This crab is known worldwide for out-competing other crustaceans like Dungeness Crab and eliminating eelgrass beds. Management efforts that are on hold include field work, sampling, capture and removal, training, and establishing more early detection sites. Postponing trapping to at least mid-April could mean some prime capture times will be missed.

There is concern for the safety of the volunteers who are older retirees, who may be more susceptible to the coronavirus because of their age. “We’re not asking people to do anything they’re uncomfortable doing, and any participation is elective,” said Emily Grason, a marine ecologist and the University of Washington’s Crab Team program manager.

Learn more at sequimgazette.com.

trapped green crabs
Credit: Adrianne Akmajian, Makah Tribe Fisheries Management

National Invasive Species Awareness Week 2: May 16 – 24

The goal of NISAW Week 2 is to connect individuals and public officials with local organizations who offer invasive species removal, restoration, or awareness events and opportunities. Ultimately, the North american Invasive Species Management Association (NAISMA) wants to create positive outcomes in habitats through education, legislation and local action. NAISMA provides tools to help organizations:

NISAW Toolkit: https://www.naisma.org/programs/nisaw/#toolkit.


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:

  • May 20 – Kurt Dreisilker, Morton Arboretum: How the Morton Arboretum approaches invasive species prevention and EDRR – REGISTER
  • June 17 – Forest Eidbo, Minnesota DNR: Making educational signage that people actually read, according to the experts – REGISTER
  • July 15 – Gary Lovett, Cary Institute of Ecosystem Science: Invasive forest pests in the U.S.: Impacts and policy solutions – REGISTER
  • August 19 – How biocontrol agents are approved and how to access them for your invasive species management needs (go to NAISMA 2020 Webinar Schedule page to register.
  • September 16 – Leaps and Bounds – How to jump over the barriers to preventing the spread of invasive species – REGISTER


Invasive Spotlight:
Malta Star-thistle
(Centaurea melitensis)

Malta star-thistle is an annual (rarely a biennial) that occurs in open, disturbed sites such as grasslands, rangeland, open woodlands, fields, pastures, roadsides, waste places and fields. It is a native of southern Europe and northern Africa. It crowds out native plants, and its spiny flower heads can make it painful to walk through. High infestations of star-thistle can cause water stress in native species even in years with normal rainfall.

Malta star-thistle grows as a rosette when young in winter and produces a spiny, yellow-flowered head that typically reaches 1 m tall. As a rosette, it can be distinguished from other similar species by its lobed simple leaves whose lobes are smoothly rounded and terminal lobe is usually simple, broad, and rounded or oval. Other rosettes with which the species might be confused usually have either more angular lobes, or the lobes are further toothed, serrated, or divided. The leaves start off quite small in mid-winter and subsequently grow to 3” to 5” (7.5 to 13 cm) as the rosettes enlarge. The rosette may also have a fuzzy whitish center. Rosette leaves typically wither by flowering time. The flower stems are stiff and openly branched from near or above the base (sometimes unbranched in very small plants). Stem leaves are alternate, and mostly linear or narrowly oblong to oblanceolate. Margins are smooth, toothed, or wavy, and leaf bases extend down the stems (decurrent) and give stems a winged appearance. The yellow "flower" is actually many flowers (the plant is a composite or asteraceous) and it looks as though it is trying to squeeze out of the flower base: it never widens like a dandelion flower.

Control is easiest when the plant is in its rosette stage and before flowers open. Small infestations can be controlled by hand. Larger infestations may require herbicide application. The same methods used to control yellow star-thistle (Centaurea solstitialis) can be used to control Malta star-thistle.

Follow this link for more information on Malta star-thistle.


Credit: Howard Homan, Invaders of Texas

Malta Starthistle rosette

Credit: Chuck Sexton, Balcones Canyonlands NWR


Credit: Terri Whaley, Invaders of Texas

More News

House Cats Have More Impact On Local Wildlife Than Wild Predators
A GPS tracking study of more than 900 house cats (Felis catus) demonstrates that "when they kill small birds and mammals, their impact is concentrated in a small area, having a bigger effect than wild predators do." Learn more at NPR.org.

Tiny Fly from Los Angeles Has a Taste for Crushed Invasive Snails
A native species of tiny phorid fly, Megaselia steptoeae, has been discovered in Los Angeles, California that has a taste for smashed invasive Draparnaud's glass snails, Oxychilus draparnaudi. This is unusual because first, the majority of phorid flies whose lifestyles have been observed are parasitoids of social insects like ants, and second, the flies presumably fed on something other than this species of snail before the snail was introduced to California. Learn more at sciencedaily.com.

Gypsy Moth Larvae Love Poplar Leaves Infected by Fungi
Black poplar leaves infected by fungi are especially susceptible to attack by gypsy moth (Lymantria dispar dispar) caterpillars. A research team found that young larvae preferred leaves covered with fungal spores and grew faster and pupated earlier than those feeding only on leaf tissue. The results shed new light on the co-evolution of plants and insects, in which microorganisms play a much greater role than previously assumed. Read more at sciencedaily.com.

Analysis Identifies Most Worrisome Invasive Plants that May Arrive Soon in Northeast
More than 100 new invasive plant species could expand into the Northeast U.S. due to climate change. To help resource managers in the Northeast meet this challenge, researchers "are offering a new analysis that narrows the large list down to five priority species with the greatest potential impacts". Learn more at Universituy of Massachusetts Amherst. NOTE: their short summary publication has maps that illustrate where in Texas these species may become a problem.

Invasive Species with Charisma Have It Easier
"The social acceptance of attractive invasive species with charisma is higher than that of unattractive invasive species. This can hamper nature conservation measures designed to contain the spread of a species…" Read more at sciencedaily.com.

Great Lakes States Urge Residents to Help Stop Spread of Invasive Species
"As residents head outdoors to freshen backyard ponds and launch fishing boats, state and provincial resource managers are urging everyone to keep a few simple guidelines in mind to keep the Great Lakes safe. Each Great Lakes state and province has made its own efforts toward preventing the spread of invasive species." Learn more at greatlakesnow.org.

Northern Pike Moved into a Unique River in Eastern Wyoming, and Are Decimating Native Fish
The Niobrara River in Wyoming is home to several minnow-sized fish species that are adapted to the river's unique ecology. Now non-native northern pike (Esox lucius) have begun to move upstream, where they are devastating the populations of the native fish. Learn more at the Casper Star Tribune.

What Is the Asian Hornet Invasion Going to Cost Europe?
"Since its accidental introduction in 2003 in France, the yellow-legged Asian hornet Vespa velutina nigrithorax is rapidly spreading through Europe. Scientists have now tried to estimate the costs of the invasion regarding the potential damage to apiculture and pollination services." Read more at sciencedaily.com.

Water Hyacinth Causes National Power Outage in Uganda
"A huge floating island of water hyacinth (Eichhornia crassipes) in Lake Victoria triggered a nationwide blackout in Uganda after clogging a turbine in a hydroelectric power station." Learn more at bbc.com.

Parasite Carried by Grey Squirrels Negatively Impacts Red Squirrel Behavior in Europe
"Research reveals a new mechanism of how grey squirrels affect native red squirrels in Europe through parasite-mediated competition. " Read more at sciencedaily.com.


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.

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.

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