Biologically Based Technologies for Pest Control Page: 49
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Chapter 3 The Technologies 49
(grobacterium spp.) and affecting crops such as
grapes. No pesticides work against this disease
(138). Strains of a related species (A. radio-
bacter) suppress the disease, but each strain
works only against certain disease strains. Two
microbial pesticides for crown gall are sold in the
United States, Galltrol by the AgBioChem Com-
pany and Norbac 84C by the NorTel Lab, with
annual sales exceeding $100,000 (138).
In 1994 at least three new microbial products
that enhance plant growth, in part by suppressing
root-dwelling bacteria, came on the market:
Kodiak, Epic, and Quantum 4000 from the
Gustafson Company (138). These seed treat-
ments, which colonize growing roots once seeds
germinate, are used in combination with chemi-
cal fungicides. Sales in 1994 were for seeds suf-
ficient for planting three million to five million
acres of cotton, peanuts, and beans; this figure is
expected to expand to 20 to 30 million acres by
the year 2000 (138). The first commercial prod-
ucts for control of postharvest plant disease
(which blemishes and causes rot on harvested
crops) are just now coming on the market also.
Bio-Save 10 and 11 (products based on the bac-
terium Pseudomonas syringae from EcoScience
Corporation) and Aspire (product based on the
yeast Candida oleophila from Ecogen) became
available in 1995 for control of major posthar-
vest diseases of apple, pear, and citrus (161).
Disease-suppressive soils and composts
reduce crop diseases, it is thought, through the
action of bacteria, fungi, or other microbes that
dwell in these materials. Suppressive soils occur
naturally in some areas or can be created by spe-
cific farming practices. Almost all are main-
tained by individual farmers, and no commercial
products are available (138). Suppressive com-
posts are widely used in horticulture but are not
advertised for their disease-suppressive charac-
teristics.
Pastures, Rangelands, and Forests
Pest problems in these habitats pose special
problems. The lands generally are of lower eco-
nomic value, making it difficult to justify the
costs of expensive pest control programs basedon conventional pesticides. Many forests and
rangelands also encompass environmentally sen-
sitive habitats, such as those adjacent to water-
ways, where use of pesticides may be restricted
or prohibited. The most commonly used BBTs in
these areas are various forms of biological con-
trol because of the low costs and general lack of
impacts on nontarget organisms.
Rangelands and pastures are two of the few
areas where BBTs currently are used for weed
control. Classical biological control agents have
been introduced against 40 U.S. weeds. Cur-
rently the approach has provided some level of
suppression for 18 weeds and excellent control
over some or most of the range of seven of these
species (420). The successes include musk thistle
(Carduus nutans), controlled by the weevil Rhi-
nocyllus conicus, and skeletonweed (Chondrilla
juncea), by Puccina chondrillina (420).
A number of programs propagate and distrib-
ute weed natural enemies to enhance their
effects. The Oregon Department of Agriculture's
weed program has introduced 42 natural enemies
against 20 target plant pests since it began in the
1970s. Program staff now collect and transfer
biological control agents across weed-infested
areas to maximize the agents' impacts. In Mon-
tana, county extension agents cooperate with
high schools and local 4-H clubs to run a similar
program involving high school students (266). At
least seven commercial suppliers now harvest
weed biological control agents collected from the
field for sale to ranchers, land managers, and oth-
ers (155).
Rangeland managers sometimes modify live-
stock grazing practices to help reduce weed pop-
ulations. The extent and the effectiveness of this
practice are unclear. In areas managed to con-
serve native biodiversity, the use of livestock to
help reduce weeds is sometimes undesirable
because the cattle do not confine their impacts to
target weeds (332). Under some circumstances,
however, cattle grazing can enhance plant biodi-
versity. Other BBTs for weed control are not yet
in use. Plant diseases have been evaluated as
potential microbial pesticides for five weeds of
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United States. Congress. Office of Technology Assessment. Biologically Based Technologies for Pest Control, report, September 1995; [Washington D.C.]. (https://digital.library.unt.edu/ark:/67531/metadc39770/m1/55/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.