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  • Invader of the Month_May 2005
    again Mute Swans a native of Asia are the largest species of waterfowl in the Chesapeake Bay region and one of the world s most aggressive bird species Their aggressive behavior has led to the displacement of native birds from nesting and feeding areas Mute swans were responsible for driving the last remaining colony of Black Skimmers from the Chesapeake Bay and for eliminating important tern nesting habitats But it is in the Chesapeake s underwater grass beds that the mute swan is having the most devastating effect Already reeling from decades of water quality degradation this important aquatic ecosystem is now being devoured at an alarming rate by the Chesapeake s burgeoning mute swan population The current population eats an estimated 10 5 million pounds of aquatic grasses every year If the population is allowed to double again the level of consumption and disruption will rise accordingly Aquatic grasses are the base of most of the food chains in the Chesapeake estuary and many plants and animals depend upon them for survival including many commercially important species Native waterfowl graze the same grasses but are only in the Chesapeake Bay region for over wintering Because mute swans are in the Chesapeake year round they spend the summer eating the new plants that are critical for the re establishment of aquatic grass beds Grass bed restoration a key component in the effort to restore the Chesapeake Bay has been severely hampered by mute swans who can wipe out a restoration planting in a few days Animal rights groups have chosen the mute swan as a favorite cause alleging that State and Federal wildlife agencies are using the mute swan as a scapegoat for environmental problems despite the fact that dozens of mainstream conservation groups including the Audubon Society and the

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  • Invader of the Month_April 2005
    to a very aggressive difficult to control weed and has earned Canada thistle the designation of Invader of the Month for April by the Maryland Invasive Species Council Canada thistle has dark green leaves which are oblong variably lobed with spiny edges and are attached to the stem alternately Canada thistle has grooved slender stems which are green or black It grows to a height of 3 5 feet tall branching at the top with numerous rose purple flowers clustered on the top of them Unlike the other thistles which start from seed each year Canada thistle can spread not only from seed but also through an extensive deep horizontal perennial root system which has vegetative buds that producing new plants as it creeps through the soil These horizontal and vertical root systems can reach depths of 6 15 feet Due to this extensive root system Canada thistle generally grows in distinct patches Introduction of this weed to new areas can be from the windborne seed spreading root systems movement of contaminated hay or soil or equipment In Maryland emergence generally occurs in early to mid April starting first as a rosette then with rapid growth culminating with flowering and seed production in mid May through June After seed production Canada thistle will continue to send nutrients to the roots to build its reserves and in the heat of summer will dry down some As the fall weather turns cooler and moisture is available a second flush of Canada thistle will occur but with limited flowering The numerous seeds generally 1 000 1 500 per plant can have a high germination rate They can remain viable in the soil for up to 20 years but most germinate within one year The seeds are attached to a cottony pappus commonly known

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  • Invader of the Month_March 2005
    three most common Amur Morrow s L morrowi and Tatarian L tatarica were all introduced into the United States as ornamental plants They have increasingly spread into natural areas in the Northeast and Midwest states where they can form dense thickets that compete for space light and nutrients with both native trees and wildflowers reducing the numbers and diversity of those plants Although they can invade undisturbed forest they are more often found in hedgerows forest edges in forested floodplains and other disturbed areas with higher light levels Bush honeysuckles are upright deciduous multi stemmed shrubs that can grow to 15 ft They have simple opposite entire sometimes hairy leaves that emerge earlier in the spring than leaves on native shrubs giving the invaders a growth advantage early in the season Their flowers are tubular whitish yellow or pink less than 1 long growing in pairs in the leaf axils Flowers usually appear in April although the bushes can bloom as early as March and as late as June depending on the species Their fruit appearing in the summer is usually red rarely yellow Exotic bush honeysuckles can usually be distinguished from our native shrub honeysuckles by their hairy styles the upright extension of the seed forming structure deep in the center of the flower and by their hollow stems There is one more exotic honeysuckle Japanese honeysuckle L japonica that is a very common mid Atlantic invader but it is a vine not a shrub Invasive honeysuckles reproduce almost entirely by seed which is widely disseminated by birds and small mammals Exotic honeysuckle fruit may not be a preferred food source for birds but Tartarian and Amur honeysuckle fruits often remain on the bushes late into the winter when other food for overwintering birds is gone For migrating birds

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  • Invader of the Month_February 2005
    Archived Invaders In the News Invasive Species of Concern in Maryland Information and Resources The Lesser Celandine IOTM has been updated and re issued Please visit the April 2012 Invader of the Month Click here to view the archived February

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  • Invader of the Month_January 2005
    Month Archived Invaders In the News Invasive Species of Concern in Maryland Information and Resources The Nutria IOTM has been updated and re issued Please visit the April 2009 Invader of the Month Click here to view the archived January

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  • Invader of the Month_November 2004
    rust caused by the fungus Puccinia horiana is a very destructive disease of many chrysanthemums and related species including pot mums spray mums and garden mums The pathogen is not established in the United States or Canada but a recent isolated introduction into Maryland qualifies this pest as the Maryland Invasive Species Council s Invader of the Month for November The disease originated in eastern Asia and eventually spread to Europe Africa Australia Central America and South America Local outbreaks of the disease have occurred in both the United States and Canada however successful detection and eradication processes have kept the disease from being established In 2004 chrysanthemum white rust was found in one nursery in Maryland Eradication was quick and successful preventing the disease from causing extreme losses in the nursery industry or becoming established in the State In countries where the disease occurs weekly fungicide treatments are needed to manage the disease which is costly The first visible symptoms of chrysanthemum white rust are small white to yellow spots up to four millimeters wide on the upper surface of the leaf They may be slightly sunken or dimpled and become brown over time Pustules develop on the underside of the leaf beneath the small spots The pustules originally appear as buff to pink colored but become white as they mature giving the disease its name Symptoms usually develop during cool wet weather appearing 5 to 14 days after infection Hot dry weather or the application of fungicides can mask or suppress disease development This fungus only grows and reproduces on chrysanthemums and related species New infections are initiated by spores released from pustules during periods of high relative humidity and when temperatures are between 40 and 73 F Spores are spread from plant to plant mainly by splashing

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  • Invader of the Month_October 2004
    as Invader of the Month by the Maryland Invasive Species Council for October 2004 Known scientifically as Polygonum perfoliatum MAM is a sun loving plant that prefers moderate to full sunlight and moist conditions It invades forest edges stream banks wetlands roadsides uncultivated fields fence lines and other disturbed open sites It grows very rapidly scrambling over low vegetation and up tree branches into the canopy Thick blankets of MAM vines smother and kill native plants by blocking light and preventing photosynthesis The stems and leaves of MAM are armed with downward pointing hooks or barbs which help it hold onto vegetation as it climbs These barbs also make it difficult to walk through infested areas and painful to remove MAM by hand The leaves are distinctly shaped like an equilateral equal sided triangle and alternate along the narrow delicate stems Like most polygonums a small collar like structure surrounds the stem at each node Flowering begins in June or July and continues through the growing season The small light green inconspicuous flowers are followed by clusters of colorful blue purple fruits each containing a single glossy black or reddish black seed Birds are attracted to the colorful fruits of MAM and are apparently its primary long distance dispersers MAM seeds are transported locally by ants that are attracted to a small food body on the seeds The ants feed only on the food body and may help the survival of MAM by inadvertently planting the seeds Water may also play an important role in dispersal Its fruits can remain buoyant for 7 to 9 days and may be carried during flood events Weevil to the rescue A biological control agent has been investigated for control of MAM and is planned for a test release into the wild in Delaware

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  • Invader of the Month_September 2004
    Invasive Species Council has selected them as Invaders of the Month for September GAS is an amusing acronym for yet another potentially serious threat to American agriculture ecosystems and human health Giant African Snails or alternately Giant African Land Snails GALS are several huge species in the genus Achatina One Achatina fulica can have an eight inch long shell and weigh up to two pounds Because of their large size ease of care and attractive shell patterns these snails are tempting subjects for classroom study and the ever expanding exotic pet trade However they are illegal in the United States GAS eat a wide variety of more than 500 plant species including many agricultural fruits and vegetables They have great reproductive potential laying several hundred eggs at a time and producing three or four times per year The snails are hermaphrodites having both male and female organs so any two can mate and both could produce eggs They can also live up to nine years Three snails smuggled into Florida in 1966 grew to a population of almost 18 000 in 10 years and were finally eradicated at a cost of 1 million The snails also present some public health concern since like other snails and slugs they can carry parasites such as Angiostrongylus cantonensis a tiny rat lungworm This parasite which could be transmitted to humans can produce a rare form of meningitis in those who improperly cook or handle the snails although according to the Centers for Disease Control the illness is not usually serious This parasite is presently established in portions of Louisiana Recently the U S Department of Agriculture seized numerous GAS from classrooms pet stores a snail farm and other sources in several states Teachers and others have voluntarily surrendered specimens after realizing they also

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