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RE: Mustards as fumigants
I personally agree with you about the value of brassicas as alternatives
to soil fumigants but would like to remind us all that green manures in
general have the value of generally feeding the bottom of the soil -
detrital food chain which must promote an increase in soil respiration,
competition, antibiosis, and at some point, biodiversity. Most any
green manure crop when turned under green and young is, therefore, apt
to have a beneficial effect on the disease problem potential situation
on following crops. When we select soil fumigant act alike green
manures such as the brassicas and sudan grass, we get the double effect
of direct initial mortality to most anything in the soil including the
disease causitive organisms we are concerned about plus apparently some
species of small seeded weeds followed by a great energy rich food
source for recolonizing saprophytes and food wed they support.
Otherwise they would be of limited ecological value - just home grown
cheep fumigants.
I still believe that we are missing the boat by talking about
"alternatives to Methyl Bromide". The fact is that Methyl Bromide IS
the alternative; the alternative to good husbandry and soil health. And
thanks for your excellent article in IPM Practitioner, it informed and
inspired a lot of people.
>----------
>From: Joel Grossman[SMTP:0003216125@mcimail.com]
>Sent: Wednesday, June 05, 1996 9:52 AM
>To: sanet-mg
>Subject: Mustards as fumigants
>
>I was at the methyl bromide alternatives conference, and if my memory
>is
>correct, the problem with brassicas like mustard as a soil fumigant is
>that
>they are phytotoxic to strawberries.
>
>But for many other crops, mustards make good soil fumigants,
>particularly
>when combined with solarization. The plastic tarp used in solarization
>holds in the toxic gases that arise from the decomposition of the
>mustards
>[and other cole crop residues, including cabbage], providing quicker
>and
>better results than without tarping.
>
>The key with strawberries is some R&D to find out the cause of
>toxicity,
>and then find a plant variety that can be used as an alternative
>fumigant
>for the crop. But this line of research is, to the best of my
>knowledge,
>not being pursued.
>
>By the way, there is a 10-page article titled "Brassica Alternatives to
>
>Herbicides and Soil Fumigants," with a page of references on the
>subject,
>in the July 1993 IPM Practitioner [BIRC, Berkeley, CA, 510/524-2567;
>last I
>checked they were selling back issues for $5, if you're really
>interested
>in the subject]. I thought then, and still think now, that the concept
>of
>grouping fumigant green manure/cover crops is a good one. The major
>limitation is that when dealing with home-grown botanical products,
>there
>will be variations in levels of the toxicants in the plants and
>efficacy
>due to climate, soil, growing conditions etc. Also, these plant
>chemicals
>are not always benign -- remember the famous mustard gas of World War I
>was
>a product of these same brassicas.
>
>Joel Grossman
>disclaimer: I wrote the brassica article for the IPMP referred to
>above.
>
>