Contents:
Narrow Corn Rows | Potato Thresholds | Atrazine
biopiles away
Land-farmed pesticides | Cabbage looper IPM | Midseason corn action
Less chemicals on carrots | Bt resistance in borers | Bees
attack mites
The many projects featured in this special PRO section are only a sampling of
AURI-funded efforts to reduce farm pesticidue use. Other projects funded under the second
through fourth rounds of PRO are summarized below. Some have completed their research and
field tests; others are still active. For the results of PRO round one, refer to the July
1996 issue of Ag Innovation News or contact Donna Christianson at 1-800-279-5010.
Narrow crop row spacing adoption
PRINCIPAL INVESTIGATOR: Gregg Johnson, Southern Experiment Station.
COOPERATORS: Waseca County Corn Growers, Southern Experiment Station, John Deere
Des Moines Works.
PURPOSE: To integrate narrow crop row spacing with banded herbicide and
cultivation in order to improve herbicide management in corn and soybeans.
KEY RESULT: Even in narrow row systems, cultivation appears the single most
important weed management strategy for reducing herbicide use and increasing corn yields.
As a result of this research, producers are in a better position to consider a banded
application of herbicide with cultivation to cut weed control costs. Considering that 1350
to 2100 southern Minnesota farmers cultivate, a banded application could save as much as
$7,000 per farm.
SUMMARY: Most growers using narrow row systems rely on broadcasting herbicide at
the full labeled rate. This research showed, however, that corn yield was just as good
when using a below-label rate broadcast or a full-rate band application of herbicide, as
long as cultivation was used to supplement weed control. Weeds germinating after
cultivation are far less competitive with the crop.
Aphid thresholds for PLRV control
PRINCIPAL INVESTIGATOR: Ted Radcliffe, U of M Entomology.
COOPERATORS: Red River Valley Potato Growers Association, U of M, Area II Potato
Growers Association, MN Department of Agriculture.
PURPOSE: To set cultivar-specific action thresholds for green peach aphids,
which can be used to time insecticide applications to prevent potato leafroll virus in
processing potatoes.
KEY RESULT: With the exception of Goldrush, potato cultivars tested did not
differ greatly in susceptibility to potato leafroll, which largely validates the
established action threshold of 30 peach aphid apterae in 100 leaves.
SUMMARY: Growers spray on a calendar schedule or use an action threshold (30
apterae per 100 leaves) developed specifically for Russet Burbank, a cultivar highly
susceptible to both PLRV and net necrosis (which produces dark chips and fries).
Since most cultivars do not develop net necrosis, it was thought they were more
resistant to PLRV, and that developing cultivar-specific thresholds would result in less
insecticides used to control PLRV-carrying aphids. Contrary to expectation, the study
confirmed that PLRV susceptibility was similar for eight commercial processing cultivars
in Minn. and N.D.: Atlantic, Cascade, Norchip, Ranger Russet, Russet Burbank, Russet
Norkotah, Shepody and Snowden.
Goldrush, however, was extremely susceptible to PLRV and the thresholds established for
seed potatoes may be necessary for this cultivar.
Compost bioremediation for contaminated soils
PRINCIPAL INVESTIGATOR: Paul Bloom, U of M Soil Science, Water and Climate.
COOPERATORS: Western Minnesota Sustainable Farming Association,
U of M, MN Department of Agriculture.
PURPOSE: To determine whether soil highly contaminated with atrazine could be
detoxified safely and rapidly in a biopile as opposed to "natural" degradation
in soil and traditional composting.
KEY RESULT: Since biopiles are less expensive to design and maintain, this
remediation method may be more desirable than composting; researchers say biopiles are
substantially less expensive than landfilling and incineration.
SUMMARY: Biopile technology has the potential to detoxify high concentrations of
pesticides in soil and prevent further environmental contamination. In this lab research,
similar amounts of extractable atrazine were degraded in both compost and biopile
environments.
Biopiles stimulate the growth and activity of native soil microorganisms rather than
the "heat loving" microbes characteristic of traditional composting. Biopiles
are constructed by excavating contaminated soil, adding nutrients and organic amendments,
and aerating through buried PVC pipe or drain tile. They can be covered or underlain by
plastic sheeting to prevent runoff and leaching. The biopile is allowed to react for
several months with minimal maintenance.
Biopile technology is suggested for soils that cannot be land-applied. The Minnesota
Department of Agriculture has identified more than 100 Minnesota pesticide spills that
need biopiling. If savings estimates are verified, biopiles will lower cleanup costs -- 90
percent of which are paid for by taxes levied on farmer-applicators and co-ops purchasing
pesticides.
Land farming for pesticide remediation
PRINCIPAL INVESTIGATOR: Paul Bloom, U of M Soil, Water and Climate.
COOPERATORS: Western MN Sustainable Farming Association,
U of M, MN Department of Agriculture.
PURPOSE: To develop an effective methodology for land application remediation of
pesticide-contaminated soils.
KEY RESULT: A 4X application rate of alachlor-contaminated soil (8 pounds per
acre of active ingredient) can safely be applied to farmland for a depth of 5 inches.
Alachlor's half-life is 9 to 17 days; in land application, it dissipates in approximately
90 days.
SUMMARY: The first year of this study established lab degradation rates and
leaching potential. The next step, a field demonstration, is to assure that degradation
occurs before the pesticide is transported below the soil profile, and that potential crop
damage is limited to under one year.
The former Isanti County Cooperative in Cambridge, Minn. has 750 cubic yards of
excavated sandy soil containing alachlor (Lasso) at concentrations considered too high for
land application with currently approved methods. That soil is being spread on a farm test
site and planted with soybeans. Soybeans make a good cover crop because they're resistant
to alachlor. To establish an adequate cover crop, alachlor concentration in the seed zone
may not exceed 6 ppm. (The soybeans will not be harvested but, rather, plowed down).
Reducing pesticide use in cabbage
PRINCIPAL INVESTIGATOR: William Hutchison, U of M Entomology.
COOPERATORS: MN Fruit & Vegetable Growers Association,
U of M.
PURPOSE: To develop and implement a biologically based IPM system for cabbage,
with emphasis on cabbage looper. Objectives include increasing native parasite levels,
developing action thresholds, and field-testing previously developed thresholds.
KEY RESULT: Data analysis showed consistent moth arrival for cabbage looper,
which provides for more efficient scouting. In addition, the biorational product
"Spinosad" provided good pest control in 1996 field studies.
SUMMARY: Data analysis over six months showed cabbage looper moths' consistent
migration, with the first date of arrival between July 3 and July 11. An average of 173
degree days (10 degrees F or higher) pass between moth arrival and detection of eggs or
larvae. Knowledge of consistent moth arrival and number of degree-days before egg/larvae
stage provides a more reliable early warning system and allows more efficient use of
scouting resources.
Because Bt products are inconsistent on the high-level control necessary in
fresh-market production, Spinosad replaced the Bt product Javelin for this project.
Spinosad has consistent efficacy against cabbage looper and less impact on beneficial
predators and parasites. At 100, 75, and 50 percent of label rate, Spinosad provided good
to excellent protection against cabbage looper, diamondback moth, and imported
cabbageworm.
Reducing pesticide use in sweet corn
PRINCIPAL INVESTIGATOR: William Hutchison, U of M Entomology.
COOPERATORS: MN Fruit & Vegetable Growers Association, U of M, Southern
Experiment Station, Pillsbury/Green Giant.
PURPOSE: To develop hybrid-specific action thresholds for European corn borer in
relation to crop growth stages, and to establish the timing of reduced pesticide rates for
common rust, taking hybrids' genetic resistance into account.
KEY RESULT: Hybrid-specific thresholds have been established for ECB treatment
in "midseason" hybrids such as Jubilee, and fungicide applications have been
shown to be economically reducible for rust-resistant corn. The annual savings for
adopting both management techniques is estimated at $2.1 million.
SUMMARY: ECB treatment thresholds have been recommended for mid-season sweet
corn hybrids such as "Jubilee," ranging from 25 to 50 percent for whorl stage to
5 percent for early tassel or silk stage. Jubilee continues a dominant hybrid in the
Midwest and is representative of most mid-season hybrids.
These results are projected to impact 100,000 acres, or a 75 percent adoption rate over
85 percent of the state's total corn acreage. The traditional four insecticide sprays per
season average can be reduced to 1.5 sprays, for annual savings of $1.8 million.
It has also been confirmed that the fungicide "Tilt" can be reduced for
hybrids Jubilee and Merit, which have at least partial resistance to rust. For common rust
control, fungicide applications could be reduced by 50 percent. Projecting a 75 percent
adoption rate over the 140,000 acres in Minnesota typically subjected to late-season rust
pressure, $346,500 in annual savings may result.
Reducing pesticide use in carrots
PRINCIPAL INVESTIGATOR: William Hutchison, U of M Horticulture.
COOPERATORS: MN Fruit & Vegetable Growers Association
(two growers), U of M, U of Wis.
PURPOSE: To manage aster yellows disease in carrots by monitoring various aster
leafhopper (ALH) vectors and soil nitrogen levels and responding with minimal insecticide
applications when appropriate.
KEY RESULT: Adequate data is now available for establishing a practical,
statistically valid sampling plan for ALH in carrots. Instead of the traditional 100
sweeps/field, 40 to 60 sweeps have proven to be adequate.
SUMMARY: PCR, or polymerase chain reaction, tests for the DNA
"fingerprint" of the yellows supplies an infectivity estimate within 1 to 2
days, a major advantage over the 3 weeks for a conventional greenhouse bioassay. However,
a comparison of the two techniques found marked differences for most of the leafhopper
collections; the reason is not yet known.
Forked carrot yield appeared higher when insecticide was not applied, suggesting that
aster yellows disease may induce forking; further study is needed to confirm.
Managing Bt resistance: European corn borer
PRINCIPAL INVESTIGATOR: William Hutchison, U of M Entomology.
COOPERATORS: MN Fruit & Vegetable Growers Association,
U of M.
PURPOSE: To understand how the European corn borer (ECB) develops resistance to Bacillus
thuringiensis (Bt), and develop management techniques to reduce resistance rates.
KEY RESULT: If field populations of ECB were to develop resistance to
Bt-engineered corn, the resistant ECB population could in part be managed by not planting
Bt corn in the problem area for 1 to 3 years.
SUMMARY: The study confirms there is a cost to ECB for developing Bt resistance,
including the possibility of reduced egg lay, reduced ability to mate or slower
development. Although ECB was found to have cross resistance to some new Bt toxins, there
has been no sign of cross resistance to commercially available Bt strains. In 1996 field
trials, Bt-engineered sweet corn showed a phenomenal 99.9 percent level of control of the
ECB, with no additional protection from conventional insecticides.
Honey bee breeding program
PRINCIPAL INVESTIGATOR: Marla Spivak, U of M Entomology.
COOPERATORS: MN Honey Producers Association (2 commercial beekeepers), U of M,
Wisconsin Beekeepers Association.
PURPOSE: To continue development and implementation of an IPM system to control
parasitic mites in honey bee colonies, chiefly through the breeding of
"hygienic" bees which have the genetic trait for removing mite infested pupae.
KEY RESULT: It appears that environmental conditions, such as higher mite
numbers, foraging or weather conditions, influence the response of hygienic bees. Some of
the same colonies which removed low numbers of mites in 1995 removed significantly more
mites in 1996.
SUMMARY: Instrumentally inseminated hygienic queens are used as breeder stock,
but commercial beekeepers use naturally mated queens in production colonies. Colonies
headed by open-mated hygienic queens were found to be healthier and higher in honey
production than those headed by non-hygienic queens.
USDA-ARS has now requested cooperation in large-scale field tests of formic acid to
treat varroa and tracheal mites. Tests will be conducted using the acid in a gel form,
which is safe for use by humans and nontoxic to bees. Depending on results, formic acid
may be registered for use in bee colonies by the end of the year. Testing will be carried
out by researchers in New Jersey, Pennsylvania, Texas, and Nebraska, as well as Minnesota.
Other PRO projects featured elsewhere in this section include:
* Weed seedling predication software (WeedCast)
* Bioeconomic weed management expert system (WEEDSIM)
* Controlling kidney bean root rot
* Weed competitiveness of canola varieties
* Reduced fungicide use on wild rice
* Reduce severity of wild rice diseases
* Mite management in Minnesota apples
* Extending and expanding fruit IPM
* Strawberries: a new production paradigm
* On-farm pesticide reduction strategies
Two projects, leafhopper-resistant alfalfa and remediation of mixed pesticide spills,
are in the beginning stages and do not yet have results. They will be featured in future
issues.
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