Mineral Coating Could Cut
Chemical Use in Agriculture
By Judy McBride
November 1, 2000
KEARNEYSVILLE, W.Va., Nov.
1--Tomorrows orchards and vineyards--even row crops--may have a
ghostly appearance, based on studies spearheaded by
Agricultural Research Service
Researchers at ARSs Appalachian
Fruit Research Station in Kearneysville, W. Va., and collaborators have
controlled insects and diseases and prevented sunburn and heat stress by
covering fruit trees, vines or vegetable crops with a white, reflective coating
of a specially processed kaolin--a type of clay.
Cooperative research and development between ARS and
Engelhard Corporation of Iselin, N.J.,
is producing kaolin-based products that could turn out to be among the most
versatile agricultural products ever to hit the market, said ARS
administrator Floyd P. Horn. The agency is the U.S. Department of Agricultures chief
And uses for kaolin films dont end here, according to ARS soil
scientist Michael Glenn who conceived of many of their agricultural
applications and initiated the cooperation with Engelhard. He and coinventor
Gary Puterka see kaolins potential as a carrier for just about any
chemical used on the farm--pesticide, herbicide or pheromone.
It can serve as a matrix to hold chemicals on the plant or soil and
get more even distribution, said Puterka, an entomologist. You may
be able to reduce the active ingredient by 50 percent or more. The latest
patent application jointly filed by ARS and Engelhard covers this use of
The first commercial product--Surround Crop Protectant--went on the market
in 1999 after pear growers learned that it controlled pear psylla, a
devastating insect that is becoming pesticide resistant. This year, Engelhard
upgraded it to a wetable powder formulation called Surround WP.
Since kaolin is a physical barrier, it must be reapplied to cover new growth
or after a heavy rain, which limits its feasibility in rainy areas.
However, the severe mid-Atlantic drought of 1999 proved another advantage of
the kaolin film in orchards. Treated Empire trees produced apples averaging 17
percent larger than fruit from untreated trees--even trees that were irrigated,
said Glenn. And there was no loss in number of fruit. Sekel pears reacted a
little differently: Film- covered trees doubled the number of fruit with no
loss in fruit size.
Glenn explained that the specially processed kaolin coat reflects the
heating infrared wavelengths, as well as the burning ultraviolet rays.
Its the ability to keep the tree cooler under a blazing sun that
On the West Coast, kaolin film prevented sunburn on apples and walnuts,
Glenn added. Sunburn damage makes a perfect niche for rot organisms. So packers
pay bottom dollar for produce with blemished skin or shells, or reject it
altogether. In studies here and in South America, South Africa, and
Australia/New Zealand--the kaolin- based product has cut sunburn damage
on apples in half, on average, Glenn said.
Around the country, kaolin film has controlled well over a dozen species of
insects and mites. Studies to evaluate it against the glassywing sharpshooter
in California vineyards are in progress, and results so far look encouraging.
According to Puterka, the specially formulated kaolin particles have the
potential to work against almost any insect. The key is getting good coverage
of the crop.
And with some changes in formulation, Glenn and Kearneysville colleague
Michael Wisniewski are demonstrating that the films have potential to control
diseases in orchards or keep vegetable crops viable several degrees below their
normal threshold for frost damage.
Read more about kaolins agricultural applications in the November
issue of Agricultural
Scientific contact: Michael Glenn and Gary Puterka, ARS Appalachian
Fruit Research Station, Kearneysville, W.Va., phone (304) 725-3451, ext. 321
[Glenn], ext. 361 [Puterka], fax (304) 728-2340,