[NAFEX] Fwd: Biofumigating Apple Orchards
Lon J. Rombough
lonrom at hevanet.com
Wed Apr 12 09:49:38 EDT 2006
Begin forwarded message:
From: ARS News Service <NewsService at ars.usda.gov>
Date: April 12, 2006 6:12:15 AM PDT
Subject: Biofumigating Apple Orchards
Reply-To: ARS News Service <NewsService at ars.usda.gov>
Evaluating a Natural Fumigant for Apple Orchards
ARS News Service
Agricultural Research Service, USDA
Jan Suszkiw, (301) 504-1630, jsuszkiw at ars.usda.gov
April 12, 2006
--View this report online, plus any included photos or other images, at
Apple growers seeking to use natural substances produced by decomposing
Brassica plants to "biofumigate" their orchards may want to first
consider new findings by Agricultural Research Service (ARS) scientists
in Wenatchee, Wash.
Rapeseed, mustard and other Brassica species are gaining popularity in
Washington and California as a natural means of controlling soilborne
pests before planting time. That's because they release a variety of
chemical byproducts upon decomposing--particularly isothiocynates. But
according to Mark Mazzola, mechanisms other than biofumigation are at
work against Rhizoctonia solani, a fungal culprit behind apple replant
disease. Mazzola is a plant pathologist with ARS' Tree Fruit Research
Laboratory in Wenatchee.
Mazzola and collaborators want to improve the use of Brassicas in
integrated approaches to managing replant disease, which is
traditionally fought with chemical fumigants. In the Pacific Northwest,
this growth-sapping affliction of young apple trees can cause
diminished crop returns up to $40,000 per acre over 10 years.
In trials using ground-up rapeseed as a soil amendment, Mazzola
observed that release of isothiocynates had nothing to do with
Rhizoctonia control. Rather, the control stemmed from changes the
rapeseed caused to the soil environment and microbes living there. Some
flourished, while others perished.
For example, Pythium fungi -- another replant disease culprit -- and
Streptomyces bacteria strains that produce nitric oxide both thrived.
In plants, nitric oxide is an important signaling compound that musters
a pest-fighting response called systemic acquired resistance. Mazzola
theorizes that Streptomyces increases resulting from rapeseed
amendments stimulated this resistance response in apple tree roots,
suppressing Rhizoctonia survival long after the isothiocynates had
disappeared from the soil.
However, Pythium increases required chemical control with mefenoxam.
Thus, Brassica's pest control effectiveness isn't so clear-cut,
according to Mazzola, whose studies appear in the journal Plant
Read more about the research in the April 2006 issue of Agricultural
Research magazine, available online at:
ARS is the U.S. Department of Agriculture's chief scientific research
* This is one of the news reports that ARS Information distributes to
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* NewsService at ars.usda.gov | www.ars.usda.gov/news
* Phone (301) 504-1638 | fax (301) 504-1486
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