|
This tiny (about a quarter-inch long)
stem-boring moth, Acrolepia sp.,
is being evaluated as a biological
control for Cape ivy.
(K9423-1)
|
A fly and a moth from South Africa
may soon be enlisted to help protect natural treasures in California, Oregon,
and Hawaii. That's because these insects might serve as biological control
agents for Cape ivy, Delairea odorata.
Previously known as German ivy, Senecio mikanioides, Cape ivy was
introduced from South Africa as an ornamental vine in the late 1800s. It soon
escaped and now infests prized natural coastal areas in California up into
Oregon and native upland forests on the island of Hawaii. Willow-dominated
riparian areas in California have been among the most overrun so far.
"In its homeland, Cape ivy is hard to find," says
ARS entomologist Joseph K. Balciunas.
"That suggests there are natural insect enemies helping to limit it in
South Africa." He works in the Exotic and Invasive Weed Research Unit at
ARS' Western Regional Research Center in Albany, California.
"Because Cape ivy is uncommon there, the South Africans didn't know much
about the plant's distribution," Balciunas says. He teamed up with Beth
Grobbelaar and Stefan Neser, of the Plant Protection Research Institute in
Pretoria, South Africa, to search for natural enemies. "In 2 years of
surveys, we've more than doubled the knowledge about native locations where
Cape ivy grows. We've also identified several insects that could serve as
biological control agents here," he says.
In January, Balciunas brought two of those candidates into the insect
quarantine facility in Albany. (See "Foreign Agents
Imported for Weed Control," Agricultural Research, March 2000,
p. 4.)
The Cape ivy gall fly, Parafreutreta regalis, lays eggs in the tips of
stems, where vines and leaves would normally develop. When the larvae hatch,
they feed inside the shoots, causing the plant to produce galls (swellings)
about the size of a large marble. Although the fly may not cause much direct
damage to the ivy, it could slow the vine's ability to spread by decreasing
leaf and shoot production.
The other new arrival is a tiny moth, Acrolepia sp., recently discovered
by Neser. Its larvae—less than one-quarter inch long—form tunnels
between the layers of plant tissue in the stems and leaves as they are feeding.
"Native willows could benefit immediately if these insects keep the ivy
close to the ground by decreasing vine and leaf production," Balciunas
says. Cape ivy harms willows by overgrowing saplings and blocking out light the
trees need to survive.
Balciunas will test the insects in quarantine to make sure they don't feed on
desirable plants—a process expected to take about 3 to 4 years. "Cape
ivy is the only plant in the genus Delairea," he says, "which
makes it more likely that we'll find an insect that feeds specifically on the
weed—a key criterion for a safe biological control agent." He also
plans to test several other beetles and moths that the team discovered in South
Africa.—By Kathryn Barry
Stelljes, Agricultural Research Service Information Staff.
This research is part of Crop Protection and Quarantine, an ARS National
Program (#304) described on the World Wide Web at
http://www.nps.ars.usda.gov.
Joseph K. Balciunas is in the
USDA-ARS Exotic and
Invasive Weed Research Unit, Western Regional Research Center, 800 Buchanan
St., Albany, CA 94710; phone (510) 559-5975, fax (510) 559-5982. |
Share/Bookmark