Proceedings of the Sixty-first Annual Meeting of the Northeastern ...

84
BIOLOGY OF MULTIFLORA ROSE: AN INVASIVE SPECIES. P. Bhowmik, D. Sarkar,
and N. Tharayil, Univ. of Massachusetts, Amherst.
ABSTRACT
Multiflora rose (Rosa multiflora Thunberg ex. Murray), a member of Rosaceae, is a
stout, thorny, perennial shrub with arching stems. It is native to Japan, Korea, and eastern
China, and has been introduced into the east coast of North America, via Japan, as an
ornamental plant. During 1940-1960, this species was widely planted in the eastern US
as a wildlife plant for erosion control and as a living fence. It is widely distributed
throughout the US with the exception of the Rocky Mountains, the southern Coastal Plain
and the desert of CA and NV (Fig. 1). Multiflora rose infests more than 45 million acres
throughout the eastern US, ranging from northern TX, AK, MI, AL, and GA in the south, to
the New England coast, central NY in the north, and southern MI, WI and MN. It is able to
invade a large number of habitats, from hillside pastures, fence rows, right-of-ways, and
roadside to forest edges and the margins of swamps and marshes. Multiflora rose can
tolerate a wide range of soils and environmental conditions. It forms dense impenetrable
thickets or completely takes over the pasture. It has been classified as a noxious weed in
IL, KS, MD, MO, OH, PA, VA, WI, and WV.
Multiflora rose primarily reproduces by seeds, but it also can sprout, and form root
at the tips of arching canes that contact the ground. Mature plants may reach 3 m height
and 6.5 m diameter. Stems are reddish to green, 1.5 cm in diameter and bear numerous,
recurved thorns. Leaves are pinnately compound with 5 to 11 sharply toothed, ovate to
oblong leaflets. Petioles are 1 to 1.3 cm long with finely dissected, usually glandular
stipules. Flowers appear in large, showy, densely to sparsely flowered panicles at the
ends of the branches in late May or early June. The five petals are white to pinkish,
obvate and truncate. Fruit is an achene, and achenes are flattened, oval to obvoid,
yellowish to tan in color and enclosed in a smooth reddish hypanthium. Each cane/stem
on a large plant may contain 40 to 50 panicles, and each panicle can contain as many as
100 hypanthia or hips, and each hip, an average of seven seeds. Thus each large cane
can produce 17,500 seeds, and those seeds can remain viable in soil for as long as 20
years. Birds are the primary disperser of the multiflora rose seeds, and passing through
the digestive tract of birds enhances seed germination. Germination is also enhanced by
stratification. Seedlings begin to appear within 60 d if the soil surface remains warm.
Mechanical and chemical control methods are most widely used for multiflora rose.
Repeated mowings for several years are necessary to clean heavily infested areas. July
is the best time for mowing. Bulldozing, chaining, or brush hogging is often effective to
knock down the large established plants. European rose chalcid (seed wasp)
(Magastigmus aculeatus var. nigroflavus Hoffmeyer) and rose-rosette disease
(Phyllocoptes fructiphilus Keifer), which is spread by tiny native mite are the promising
biocontrol agents. Effective control of multiflora rose can be achieved by several
herbicides. Glyphosate at 1 to 2% (V/V), when applied in June-July gave 95 to 100%
control. Triclopyr, tebuthiuron, dicamba, picloram, and metsulfuron also gave good control
of multiflora rose. Continued monitoring of this species for its new habitats, development
of IWM strategies, and adoption of management options are important steps to restrict
this invasive weed.
66