A Little Bit of Yew Helps
When a black vine weevil eats a yew leaf, it gets more than food. The same
plant that gives the insect nutrients passes on a dose of a powerful chemical
that can, when combined with certain pesticides, lead to the bug's death.
The weevils, Otiorhynchus sulcatus, invaded the United States from
Europe in the early 1900s and are now a major pest of small fruits like
strawberries and ornamentals like rhododendrons and begonias.
Scientists suspected the yew's qualities when they noticed that pyrethroid
insecticides killed black vine weevils feeding on yew plants but not weevils on
Robert P. Doss, a plant physiologist with the
Agricultural Research Service,
"We've isolated three chemicals in the yew that act as synergists to
increase the effectiveness of pyrethroids," he says.
These are the first insecticidal synergists ever found in the yew, which has
been widely studied as a source of anticancer compounds.
Doss works in the ARS Horticultural Crops Research Unit at Corvallis,
Oregon. He collaborated with scientists at Oregon State University in Corvallis
and Washington State University in Vancouver.
Pyrethroid insecticides are synthetic compounds based on pyrethrins, natural
insecticides found in a certain type of chrysanthemum. They are popular because
they are less toxic than some other commonly used chemicals.
Pyrethroid-based products often contain a synergist to increase their
potency. For example, piperonyl butoxide dramatically increases the potency of
insecticides that kill fleas on dogs and cats by disrupting a key enzyme
involved in insecticide breakdown by the insect. Piperonyl butoxide is a
synthetic version of a compound found in sesame seeds. Doss believes the yew
insecticide synergists may work the same way.
The yew compounds have very complicated chemical structures and took nearly
a decade to isolate.
"Right now, these chemicals would be prohibitively expensive to
manufacture," Doss says. But discovering their structure paves the way for
developing cheaper synthetic versions.
Doss' next step is to test the synergist-pyrethroid combination on other
weevils, as well as on moths, crickets, and beetles that attack crops.By
Kathryn Barry Stelljes,
Agricultural Research Service Information Staff.
Robert P. Doss is in the USDA-ARS
Crops Research Unit, 3420 NW Orchard Ave., Corvallis, OR 97330; phone (541)
750-8773, fax (541) 750-8764.
"A Little Bit of Yew Helps Insecticides" was published in
the November 1998 issue of Agricultural Research magazine. Click here to see this
issue's table of contents.