Evergreens Touted as a Pesticide Buffer
11/18/99
*******************************
RELAYED TEXT STARTS HERE:
Title: Evergreens Touted as a Pesticide Buffer
Source: Environmental News Network
Status: Copyright 1999, contact source for permission to reprint
Date: November 18, 1999
Byline: John Roach
Trees, shrubs and grasses planted at the edges of a field act like a
strainer to filter droplets from the air. Farmers should plant
evergreen trees, such as pines and cedars, around their crops in
order to reduce the spread of pesticide sprays beyond their fields,
according to an Ohio State University study.
This is the first such study that compares the efficiency with which
different windbreak plants capture pesticide sprays. Evergreen trees
catch two to four times more pesticides than broadleaf plants such as
maple trees, which produce wide, flat leaves, according to the study.
As farmers spray pesticide onto crops, wind captures a portion of the
mist, which contains a wide range of droplet sizes. "The smallest
sizes can be carried off site by even a slight breeze," said Franklin
Hall, a professor of entomology at Ohio State and lead author of the
study, in a statement.
Trees, shrubs and grasses planted at the edges of a field act like a
strainer to filter the droplets from the air. To determine which type
of plants capture the most pesticides, Hall and his colleagues built
a wind tunnel at a university research lab.
The researchers hung branches of various plants inside the wind
tunnel and then sprayed dyed pesticides into the tunnel at speeds
ranging from 5 to 12 feet per second (equivalent to a light breeze)
and measured the amount of dye captured. The researchers determined
that the evergreens captured two to four times more dye than the
broadleaf plants because evergreen needles offer a larger surface
area for collecting sprays, as well as aerodynamic shape.
As the air swirls around the needles, more droplets stick to these
surfaces than if the air were gliding over the smooth surface of a
leaf, the researchers report.
"The other good thing about evergreen trees is that they don't lose
their leaves," said Hall. "So when farmers first apply pesticides in
the early spring, evergreen foliage would already be there to help
collect the spray and reduce off-site movement of pesticides." Only
the Netherlands requires its farmers to use windbreaks. The English
and Australian governments are starting to promote the idea. In the
United States, the U.S. Department of Agriculture Natural Resources
Conservation Service runs a program that assists farmers in planting
and maintaining windbreaks.