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Arundo donax Targeted by Weed Experts
By Marcia Wood
May 28, 2002
From California to Maryland, a
streamside invader called giant reed or giant cane is crowding out native trees
like alders, cottonwoods and willows. Known to scientists as Arundo
donax, this member of the grass family sports feathery white plumes called
panicles and can grow 3 to 7 inches a day, reaching 30 feet in height.
But little is known about the biology and ecology of this aggressive weed,
according to Agricultural Research
Service ecologist David F. Spencer at Davis, Calif. He is with the
Exotic and Invasive Weed Research Unit.
Spencer and ARS technician Greg G. Ksander, also at Davis, are developing
equations that predict this troublesome plant's growth at various times of its
life under various environmental conditions. During some of these stages and
climatic conditions, the weed may be particularly vulnerable to control
tactics, such as spraying it with herbicides or unleashing beneficial insects
to attack it, Spencer noted.
Fish and wildlife specialists, water-district managers and other
streamkeepers throughout the United States can apply the data derived from the
equations. That will help them pinpoint the timing that makes the best use of
herbicides, biological control insects or other tools to battle Arundo.
In one experiment, Spencer and Ksander are determining how specific
temperatures affect the plants ability to sprout. They found that
cuttings of aboveground stems and thick underground stems called rhizomes, kept
indoors in temperature-controlled growth chambers, sprouted at 57 degrees F or
68 F. At 45 degrees F, no shoots grew from rhizome sections. At that
temperature, only a single shoot sprouted from a stem cutting, but soon died.
Results from tests with rhizomes that the researchers planted outdoors at
Davis showed that shoots first appeared in late March, when the average weekly
temperature was 53 degrees F. New shoots continued to emerge until November.
The scientists will work this new temperature data into equations that relate
sprouting to temperature and to number of days elapsed.
ARS is the U. S. Department of
Agriculture's chief scientific research agency.