Researchers with the University of Massachusetts Amherst, the Nature Conservancy, and the U.S. Forest Service have been spending years developing varieties of American elm (Ulmus americana) that are resistant to Dutch elm disease (Ophiostoma nova-ulmi), the disease that devastated the elm beginning in the 1930s. Most elms succumbed to the fungal pathogen, but other than trees that have been saved through treatment with systemic fungicide, a few have survived in the wild, apparently tolerant or resistant to the disease. Using these trees as a source for new individuals, the team has developed seven varieties that can withstand Dutch elm disease. Two of these are now sold in nurseries for urban plantings.

Previous attempts to hybridize American elm with other resistant species failed because American elm has four sets of chromosomes and the other species have two sets (like humans).

In this program, seeds or cuttings are collected from survivors. Some cuttings are used to root directly. Others, made just before the tree flowers, flower under controlled conditions, which allows the collection of pollen to be used in breeding experiments. The seedlings are being tested for resistance and the ones that pass the test are being planted in forests. The idea is to establish populations of different disease resistant trees that can interbreed, which it is hoped will allow the trees to persist by evolving new resistance as the Dutch elm disease fungus itself inevitably evolves.

Learn more about this fascinating effort to restore one of North America's grandest trees.

You may not realize that in the Upper Midwest, there have not been any native earthworms since at least before the last Ice Age. All earthworms found there are non-native invaders. A new study suggests that these non-native worms are eating up the litter on the forest floor that would otherwise have accumulated, contributing to sugar maple (Acer sacharrum) die-back and perhaps harming other forest dwellers. Because ninety percent of a sugar maple's roots are within the top few inches of soil, removal of the leaf litter increases the likelihood of water stress in the maple. Read more at phys.org.

There are various systems for evaluating the invasiveness and impact of non-native species on ecosystems. Recently a novel ranking system was developed for measuring the socio-economic impact of introduced plants and animals on human well-being. The Socio-Economic Impact Classification of Alien Taxa (SEICAT) borrows from welfare economics by proposing tht alien species be classified on how they affect what people are able to do in their lives, namely their capabilities.

"Assuming that what people do in their lives represents their preferred choices of all their opportunities, SEICAT uses the magnitude of changes in people's activities for classification on a 5-point scale, from Minimal Concern (no changes in activities) to Massive (irreversible disappearance of an activity from a region)," said Professor Sven Bacher, Chair of Ecology at Université de Fribourg.

"In contrast to monetary approaches, SEICAT assessments can be made even when data are scarce; this should allow us to rank large numbers of alien species in a relatively short time," explained Dr Sabrina Kumschick, Centre for Invasion Biology at Stellenbosch University.

Read more at phys.org.

The 2017 North American Invasive Species Management Association Annual Meeting will be held October 23-26, 2017 at the Nugget Hotel and Casino located in Sparks, NV. The meeting provides one of the best professional development opportunities for invasive species professionals in North America. Come ready to learn, recharge, get a new perspective on your challenges and opportunities, and leave energized to boost your invasive species management capabilities. Early Registration ends September 1. More information and registration

A webinar on September 14, 2017 from 1 pm to 2:30 pm (Central) will focus on the interactions between drought and invasive species. Drought creates the potential for invasive plant species to increase in diversity and abundance in a variety of ecosystems, often mediated by the occurrence of disturbances (wildfire, insect outbreaks). Because the frequency and magnitude of droughts will increase in a warmer climate, scientific information on drought effects is needed to inform management and planning to ensure long-term sustainability of forest and rangeland ecosystems. This webinar will explore (1) current issues related to the effects of drought on invasive species, (2) examples of drought-related impacts on ecosystems, and (3) management options for increasing resilience.

More information on the webinar and registration is here.

A webinar on laurel wilt (Raffaelea lauricola) and the insect that spreads it, the redbay ambrosia beetle (Xyleborus glabratus), will take place on September 14, 2017 at 2:00 pm (Central), sponsored by Texasinvasives.org and USDA-APHIS. Presenters from Texas A&M Forest Service will discuss the disease and the insect. More information on registration for the webinar will be available on the Texasinvasives.org Facebook page.  (NOTE: due to impacts of Hurricane Harvey, this webinar may need to be rescheduled.)

Like most invasive plants, white mulberry causes ecological problems by displacing native plants, but it causes additional problems by possibly hybridizing with and transmitting a root disease to the native red mulberry (M. rubra). It also competes with native plants for pollinators and seed dispersers. It spreads mostly with the help of birds and other animals that feed on its berries. It was introduced to the United States from Asia in colonial times. It can grow in a wide range of conditions.

White mulberry is a small deciduous shrub or tree, although it can get to 50 ft. (15.2 m) tall. Its alternate leaves exhibit different shapes that range from ovate to mitten-shaped to deeply irregularly lobed, are 2-8 in. (5.1-20.3 cm) long, and are shiny with blunt teeth and heart-shaped bases. Plants are normally dioecious (male and female flowers on separate plants). Male flowers are small, green and occur in 1-2 in. (2.5-5.1 cm) long catkins. Female flowers are inconspicuous and crowded in short spikes. Fruit are an aggregation of berries (like a blackberry) that range in color from black to pink to white when ripe.

White mulberry is very similar to the native red mulberry, but may be distinguished by the leaves. White mulberry leaves have glossy surfaces whereas the leaves of red mulberry do not, and white mulberry leaves have bare undersides while the lower surfaces of red mulberry leaves are covered with fine hairs and soft to the touch. NOTE: the color of the berries or flowers does not distinguish one species from the other.

Follow this link to learn more about white mulberry.

Tree-Of-Heaven's Prolific Seed Production Adds to Its Invasive Potential
Tree-of-heaven (Ailanthus altissima) is an invasive triple threat, according to a new study. The species produces seeds early in its lifespan, tends to make millions of viable seeds during its life, and continues to produce seeds for decades and, in some cases, for more than a century. Read more at sciencedaily.com.

An Overlooked Seed Disperser: The Cockroach
Researchers have discovered that cockroaches can disperse seeds like birds and mammals. This unexpected discovery was made during a study of the seed dispersal mechanism of Monotropastrum humile, a small herb that thrives in the same temperate forests of Japan that the Blattella nipponica cockroach inhabits. It appears that the plant may even have evolved to be dispersed by the cockroach. Read more at sciencedaily.com.

New Non-Native Species Emerges in Great Lakes After a Mostly Clean Decade
The U.S. Environmental Protection Agency announced Monday that a new type of zooplankton, commonly reported in Europe and Asia, has been discovered in the western basin of Lake Erie. Precisely how the rotifer Brachionus leydigii arrived in the Great Lakes is not known, but contaminated ballast water discharged by oceangoing ships sailing up the St. Lawrence Seaway is a likely answer. Read more at phys.org.

Changing Tides: Lake Michigan Could Best Support Lake Trout And Steelhead
Invasive quagga (Dreissena bugensis) and zebra (D. polymorpha) mussels, invasive round goby (Neogobius melanostomus), and less nutrients from tributaries have altered the Lake Michigan ecosystem, making it more conducive to the stocking of lake trout (Salvelinus namaycush) and steelhead (O. mykiss) than Chinook salmon (Oncorhynchus tshawytscha), according to recent modeling. Read more at sciencedaily.com.

Asian Hornet to Colonize UK Within 2 Decades Without Action
The yellow legged or Asian hornet (Vespa velutina nigrithorax) -- a voracious predator of honeybees and other beneficial insects -- could rapidly colonize the UK unless its spread is combated, according to new research. Read more at sciencedaily.com.

Native Plants Need Re-Seeding After Rhododendron Removal in Scotland
In yet another example that once again emphasizes the need for restoration after the removal of major invasive plants, ecologists working in the Atlantic oak woodlands of Scotland's west coast found that – even at sites cleared of rhododendron 30 years ago – much native flora has still not returned. Instead, only dense mats of mosses and liverworts had grown. As a result, rhododendron eradication programs may require reseeding for the original plant community to re-establish. Read more at phys.org.

Afforestation with Non-Native Trees Alters Island Soils
A healthy global debate has occurred concerning the benefits of using non-native trees for restoring some aspects of ecosystem function in degraded habitats. A new study from Guam illustrates that the benefits don't always outweigh the problems the non-native cause. They found acacias planted to mitigate soil erosion changed the soil chemistry compared to that of native grasslands and forests. Read more at sciencedaily.com.

Survival of Soil Organisms Is a Wake-Up Call for Biosecurity
Tiny nematode worms in soil that attack plants have the ability to survive for at least three years stored in dry conditions, according to a recent study. Furthermore, they were found to still be able to invade plant roots. The research provides new insights into the threats posed by soil transported even unintentionally. Read more at sciencedaily.com.

Levels of eDNA of Invasive Crayfish Is Higher During Breeding Season
When monitoring invasive (in Europe) American signal crayfish, Pacifastacus leniusculus, in tanks, the levels of environmental DNA (eDNA) dramatically increased in proportion with numbers of this crayfish species when the female crayfish were bearing eggs. Read more at 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.

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

--- None scheduled.