The minute mile-a-minute mitigator

A minute of natural history

Mile-a-minute overtaking trees.
by Furryscaly via Flickr CC

Mile-a-minute (Persicaria perfoliata) is one of the most pervasive and damaging nonnative invasive plant species in the United States.  Mile-a-minute, a member of the Buckwheat family (Polyganaceae), was first introduced to the U.S. in 1890 from its indigenous range of Asian and Southeast Asia.  The plant did not successfully establish a permanent population in the U.S. until a reintroduction in the late 1930s when a Pennsylvanian nursery germinated Holly seeds from Japan and in doing so, the stowaway mile-a-minute seeds.

Approximate U.S. distribution as of July 2013. Source: Eddmaps.

www.eddmaps.org#sthash.Oa4NZqHa.dpuf

www.eddmaps.org#sthash.Oa4NZqHa.dpuf

 

 

 

 

 

 

 

 

Mile-a-minute earned its name

Mile-a-minute is an annual trailing vine with distinctive alternate triangular leaves.  Another identifying trait is the round saucer-shaped structures, or ocreae, which occur at nodes and branching points along the stem.  Self-pollinating flowers and subsequent fruit arise from the ocreae. Recurved barbs along the stem and leaf petioles make this plant particularly unpalatable to most potential herbivores.  Low predation rates in the U.S. coupled with the species’ prolific seed production and readily available dispersal mechanisms (water and birds) are traits characteristic of an exceptionally weedy plant.

Most impressing, and most ecologically damaging, is mile-a-minute’s growth rate of up to six inches a day, or 77’ (33.8 m) in a single growing season.  For perspective, mile-a-minute could cover the Statue of Liberty from heal to torch in two growing seasons.  Methods to control this invasive plant include traditional methods of manual removal and chemical pesticide applications.  However, given the rate at which mile-a-minute spreads, traditional methods are not practical of well-established or remote populations.  In 1996, the U.S. Forest Service began researching possible biological control agents.  

Following annual die-back mile-a-minute leaves and stems continue
to weigh down the plants they have climbed and shade groundcover.
by Leslie J. Mehrhoff, University of Connecticut via Invasives.org

Mile-a-minute leaves and ocreae. 
by Leslie J. Mehrhoff

  

 

Fighting nonnative with nonnative: biological control

Biological control is a way of using an invasive species natural predator or disease, most often from the species’ indigenous region, to reduce the invasives’ proliferation and dominance.  Finding a biological control agent that is truly host-specific to your target species takes a lot of research.  Inadequate research into a control agent’s life history and ecology prior to release may have dire consequences, which are worse than the original cause for their introduction.  A classic example of biological control gone awry is that of Cane Toads introduced to Australia in 1937.  Thankfully, the science of introducing biological control agents has come a long way!

Adult R. latipes are approx. 2mm long.
by Amy Diercks, via Invasives.org

Colpetzer et al. published a study in Biological Control (2004) examining potential biological control agents for use on mile-a-minute.  Results from their study supported the introduction of a small host-specific weevil from Asia, Rhinoncomimus latipes, which feeds on mile-a-minute roots as a larvae and foliage as an adult.  In 2004, the U.S. Department of Agriculture approved the use of the weevil as a biological control agent.  After several regional releases, the introduced weevils have successfully established populations throughout the Mid-Atlantic region. 

Ongoing weevil releases, such as one recently conducted in Union County, New Jersey, help sustain and expand the current weevil populations.  Led by state and county agriculture officials, the recent release of 2,000 weevils in Watchung Reservation, Union County’s largest park, is sure to reduce local mile-a-minute growth in the coming years. 
 

The below video is from a recent weevil release in New York City

Amy Diercks, Bugwood.org

Attack of the killer ladybird!

(Image via Wikimedia Commons)

No, unfortunately, there is not a Godzilla equivalent for ladybird beetles, but there is this funny cartoon.  

Now, on to the science!

 

The Science

Many of us are familiar with ladybugs.  These neat insects, more correctly termed ladybird beetles because they are not true bugs, belong to the insect family Coccinellidae.  This time of year gardeners are especially appreciative of ladybirds as the majority of species consume aphids and other pests, which would otherwise damage beloved garden plants.  However, not all ladybirds are native to the U.S.; Europe also has its fair share of nonnative ladybugs.  Several of these nonnative ladybirds are invasive – outcompeting their native counter parts. 

Asian harlequin ladybird
(Wikimedia Commons)

A recent scientific study published in the journal Science (Vilcinskas et al. 2013) indicates that the Asian harlequin ladybirds (Harmonia axyridis), originally introduced to Europe (and North America) for pest control, are now threatening the survival of indigenous ladybug species.   

Vilcinskas et al.’s found that the Asia ladybird is a carrier of inactive spores produced by an obligate parasitic microsporidia.  Although the parasite does not harm Asian ladybird, it has proven lethal to the native, Seven spot ladybird (Coccinella septempunctata).

 

Seven spot ladybird
(Wikimedia Commons)

Original publication citation:

Vilcinskas A, Stoecker K, Schmidtberg H, Röhrich CR, Vogel H. 2013. Invasive harlequin ladybird carries biological weapons against native competitors.  Science. 340(6134): 862-3.

If you are unable to access the original article, a summary article by R. Williams may be found here at The Scientist.

 

Learn More About Ladybirds & Ladybird Conservation Efforts

Spotted lady beetle on a sedge
inflorescence (By L. Shappell)

First, visit The Lost Ladybug Project - resources therein include:

• Tools for ladybug identification, including this one-page field guide.  
• I used this field guide to ID the ladybird pictured in the adjacent photo; it is an indigenous Spotted lady beetle foraging on a sedge (Carex sp.) at one of my field research sites!
• Tips on how to find and photograph ladybirds
• Instructions on how to share your photos and contribute to their citizen science ladybird surveys

To top if off, ladybirds can walk underwater!

Air packets are trapped in the tiny hairs on their feet.  When the air pockets are combined with a polymer secreted into the hairs they can stay grounded through the force of adhesion.  Learn more in this Nature News article.

(Okay, now I'm thinking Ladybird takes over Atlantis, Godzilla-style!)