Walnut Bleak

Missouri, the top black walnut producer in the USA, has enacted a quarantine to prevent the introduction of Thousand Cankers disease from the Western USA.

Fighting With Fungus

ARS News has a blurb about research efforts by ARS scientists that aim to find more efficient, reliable ways to select pathogens that will be good biological controls to fight invasive plants. Using a combination of DNA sequencing and a measurement of reaction of the plants to the pathogen, the researchers were able select pathogens that were the most species-specific, thereby narrowing down the time and resources needed to find the best biocontrol candidates. For some reason, ARS News doesn't link to the article the blurb is about, but there is an abstract elsewhere on their website. I will post a direct link to the article, which is published in the April 2009 issue of the journal Biological Control, as soon as Elsevier's website is back online :-).

Freedom Of Association

The Telegraph is reporting that hundreds of invasive crayfish have been found dead in the UK...but that's not a good thing. The Turkish crayfish (Astacus leptodactylus) is an Eastern European species that has been introduced to the UK, one of at least four non-native crayfish in UK waters. The recent deaths of the Turkish crustacean have been attributed to a disease called "crayfish plague" caused by the fungus Aphanomyces astaci. Scientists are worried that this fungal pathogen could spread to the UK's one native species, the white-clawed crayfish (Austropotamobius pallipes). The invasive Marmorkrebs crayfish also carry the disease. Unfortunately, the North American signal crayfish (Pacifastacus leniusculus) appears to be immune.

Deep Woods On

The internet is hoarding massive amounts of data, yours for the viewing if only you know where to look for it. Take for example the Exotic Forest Pest Information System For North America. A joint effort of international organizations and government agencies from the USA, Canada and Mexico, ExFor is a relatively small but incredibly detailed database of pests that threaten forest plants, from fungi and viruses to insects and other invertebrates. So far, there are only about 180 species listed in the database, with profiles for more than 140 of them. The profiles include risk assessments regarding the potential for each species to establish in North America and to cause economic damage. A complete list can be viewed here, though some of the full reports are provisional and not yet available to the public.

Blister Blues

The Tahoe Daily Tribune is reporting that white pine blister rust (Cronartium ribicola) is on the move in the Tahoe Basin, the area surrounding Lake Tahoe in California and Nevada. The rust fungus, an introduction from Central Asia, attacks sugar pine, Western white pine, whitebark pine (commonly referred to as the "five-needle" pines), and many species of currants (Ribes spp.) as well. Once infected, the trees are weakened and can die from secondary infections, insect infestations, or from the rust fungus alone.

Given the difficulty of fighting a fungal invader, which can easily spread to new trees through tiny, wind-blown spores, scientists are instead focusing on the discovery of sugar pines that are resistant to the rust. A breeding program currently in progress aims to grow as many resistant seedlings as possible so that they can be planted throughout Tahoe Basin.

If you are curious about the origin and global spread of white pine blister rust, this PowerPoint presentation from Kim Hummer will provide you with all the details.

Botox For The Birds

A story from the AP is suggesting that the recent swarm of bird deaths in Michigan are the indirect result of the proliferation of invasive species in the Great Lakes. The birds are washing ashore at Lake Michigan by the dozen, with the cause of death determined to be avian botulism (type "E"), one of several episodes to occur over the past few years. The botulism itself is not considered invasive, but scientists are speculating that it is getting to the birds through a food chain of invaders: Zebra and quagga mussels (Dreissena polymorpha and D. rostriformis bugensis) containing the bacteria that causes botulism (Clostridium botulinum) are either consumed by birds or consumed by invasive round gobies (Neogobius melanostomus), which are then consumed by birds.

I am not sure if invasive species are specifically to blame here, or if it is just that the invaders are so numerous that they now make up a significant portion of the diet of birds that frequent the Great Lakes. Are zebra and quagga mussels the only ones that can filter botulinum bacteria? Do round gobies harbor more of the bacteria than native fish? The AP article glosses over the surface of the full story, so I did some investigating and found the following hypotheses, summarized from this well-written article from Michigan Sea Grant and this one from Wisconsin Sea Grant:

• Invasive mussels create a type of habitat that is more favorable for the growth of Clostridium botulinum.
• Zebra and/or quagga mussels filter at a much faster rate than native mussel species, allowing the toxins and pathogens that they filter out to build up to a greater degree than similar-sized native species.
• The filtering power of these invasive mussels clears the water, allowing the algae Cladophora to grow. When this algae reaches sufficient numbers and then dies, the resulting anaerobic water conditions encourage the growth of Clostridium botulinum.

It is important to note that none of these hypotheses have yet been proven to be an underlying cause of avian botulism. Research continues in both the US and Canada in order that we might one day understand the cycle of bird deaths and stop it from repeating. Until then, the invasive mussels may seem the most obvious target of blame but it could turn out that the situation is much more complicated.

One Lake At A Time

In an attempt to slow the spread of VHS (Viral Hemorrhagic Septicemia) in their state, the Wisconsin Department of Natural Resources has enacted emergency regulations stating that anyone exiting a body of water must now make sure to drain his/her boat and fishing equipment. VHS, first discovered in the Great Lakes Region in 2005, infects mostly salmonid types of fishes (salmon, trout, etc.) and remains viable in water for up to two weeks, meaning that it could be spread easily by angling activities. Perhaps more frustrating for anglers is the additional rule that any fish taken away from a body of water in Wisconsin must be dead, even bait fish. As a fishing guide says in this story from WJFW, that could be a pain for anyone wanting to visit multiple bodies of water in a single day.

MultiFauceted

The Winona Daily News is reporting that an invasive snail is to blame for the thousands of waterfowl that have been found dead in the Mississippi River. Wildlife officials say that the faucet snail (Bithynia tentaculata) carries intestinal parasites - birds that ingest them can die in a single day. Unfortunately, there doesn't appear to be any way to control this European species, introduced to the US in the late 1800s, without negatively impacting native snails. At least birds of prey appear to be immune to the parasites, a good thing since eagles and other predators have been swooping in to make easy meals of the dying waterfowl.

New And Notable

The EPPO Reporting Service, in the April 2007 issue of their newsletter (.pdf only, unfortunately, so no direct links!), noted the following new arrivals:

• The emerald ash borer (Agrilus planipennis) is spreading in both the European and Far East parts of Russia. Russian ash trees are not amused...and neither are the people that planted them. The import of many Russian street trees in Russia from Canada is being eyed as one possible vector. There is more information here, if you can read Russian.
• Australia is reporting the first known instances of downy mildew (Plasmopara obducens) infecting Impatiens plants (Impatiens walleriana). Well, "busy lizzy" is an invasive in its own right, so I am not sure how I feel about that one. It cannot be good for the Aussie nursery industry though.
• Germany recently reported the discovery of three newly naturalized aquatic plants in that country: variable-leaved milfoil (Myriophyllum heterophyllum), hygrophila (Hygrophila polysperma), and lizard's tail (Saururus cernuus).

We also have two new aquatic invasive plant discoveries in the USA, courtesy of the USGS Nonindigenous Aquatic Species Alert System:

• Eurasian water milfoil (Myriophyllum spicatum) has been found in Montana, in the Noxon Reservoir and in the Cabinet Gorge Reservoir as well.
• Yellow floating heart (Nymphoides peltata) has been found in Nebraska, in a lake in Omaha.

Beeched Wail

From the Sci-Tech section over at CBS News comes this AP article about beech bark disease (BBD), a complex attack on beech trees that is threatening forests across America. First, non-native beech scale insects (Cryptococcus fagisuga) descend on American beech trees (Fagus grandifolia), covering the bark with a white waxy substance. Then, beech scale infestation predisposes beech trees to infection by fungi in the genus Nectria. Studies have repeatedly shown that there is a strong association between the scale and the fungus, though the exact mechanism allowing the fungus to attack remains unknown. To complicate things even further, it turns out that there are at least two different species of Nectria that take advantage of the beech scale attacks, one native to America (Nectria galligena) and one not (Nectria coccinea var. faginata).

Once Nectria fungus has infected a tree, dead spots occur along the trunk - sometimes appearing as oozing sores - and cause callus tissue to form (wound response), disfiguring the tree as it attempts to isolate and fight off the fungus. Under ideal conditions, a beech tree can live for years with a Nectria infection. However, infected trees are much more susceptible to environmental extremes such as drought and deep freezes, and sustain wind damage more frequently than healthy trees. Those open wounds are also ripe for infection with other fungi, and are often an "in" for damaging insects as well.

Scientists expect that as infected American beech trees die out, wildlife dependent on this forest species for food and shelter will suffer. At the very least, forest composition will be changing as BBD continues to spread. Interested readers may want to view the Proceedings of the Beech Bark Disease Symposium (large pdf) that was held back in 2004, or this article about BBD research currently underway at the University of Maine. Also, Dave Houston gave a good talk about BBD for the New England Botanical Club back in 2003 (pdf).

Tip of the virtual hat to Alan Gregory's Conservation News, by way of nuthatch.

Finch Pinch

From the Environment News Service (by way of heavy discussion on the ALIENS-L listserver) comes this article about parasites infecting Darwin's finches. The finches, theorized by Darwin to have evolved from a single species on the Galapagos Islands into 13 different species, have been infected with fly parasites, including Philornis downsi. Scientists have yet to confirm that the parasites are causing increasedmortality of the birds.