I have attached all the articles I received both over sanet
and the small fruit mail group along with my original
message so that all who are interested may learn as much
about this subject as I did.
My sincere thanks to everyone.
Dallas Co., MO
Extension Assistant/Water Quality
I recently attended one of the research stations field days
on Strawberries. There seemed to be a great dependence on
chemical fumigants to control weeds, and kill every other
living creature. It was mentioned that there is a variety
of mustard being used as a fumigant. I am interested in
finding out what variety it is.
It was also suggested that there is a fairly good cropping
rotation in use in the New York area to control diseases and
pests. I would also be interested in this information.
Thanks in advance.
Extension Assistant/Water Quality
P.O. Box 1070
Buffalo, MO 65622
All of the brassicas and crucifers and radishes have some
fumitoxic effect when used as a green manure because they
contain isothiocyanates/glucosinolates which contain sulfur.
However, some of the crops that are used more specifically
'Humus' is the variety bred for high-glucosinolates
for use as a fumitoxic green manure. Bred at Idaho
oilseed radish (Raphanus sp.) is big in Canada/Europe
mustards used as cover crops
When solarization with clear plastic is used in combination
with a fumitoxic brassica, the effect is pronounced; this
is limited to a high-value crop (such as strawberries)
as a matter of practicality though.
All of this stuff is much better in the context of a
whole-farm approach that emphasizes biological processes
such as crop rotation, composting,
green manuring, microbial inoculants, etc. rather than
a single practice (crucifer solution) within a largely
chemically-dependent farming system.
Several researchers presented results of using cole crops, particularly
broccoli, as a soil fumigant at teh 1995 Annual International REserach
Conference on Methyl Bromide Alternatives And Emissions Reductions in San
For California strawberry production, see: F. V. Sances (Pacific Ag
Research, Arroyo Grande, CA), and E.L. Ingham (Oregon State University,
For verticillium wilt control: Chang-Lin Xiao, Judith Hubbard, et al,
Dept. Plant Pathology,U California- Davis.
If you cannot find their addresses elsewhere, you may want to contact the
conference coordinator: Margie Killacky, 3425 N. First #101; Fresno, CA
93726; tel 209-244-4710.
Hillsborough County Cooperative Extension Service
University of Florida
We in New Hampshire are looking at the annual hill production
system for strawberries and have relied on Chandler as our primary
cultivar to date. In addition, about 100 strawberry growers in the state
rely on standard short-day cultivars such as Allstar, etc. Methyl
bromide use is unusual simply because there are no commercial applicators
to do the job (2 growers do have their own equipment). Most growers have
a 5 or 6 year rotation scheme that includes a year of Sudan grass as part
of the rotation to reduce nematode pressure.
For our annual hill system, we do fumigate under the plastic
mulch but not in the aisles.
William Lord (firstname.lastname@example.org)
Extension Specialist, Fruits and NH State Liaison, IR-4 and NAPIAP
Department of Plant Biology
137 Spaulding Hall, 38 College Road Fax: (603) 862-4757
Univ of New Hampshire, Durham, NH 03824 Phone: (603) 862-3203
I believe the mustard you are talking about is a rape (canola). It
is used to reduce the nematode population. Other pathogens that
fumigation kills may not be affected by only using the canola. I
know that Dr. John Halbrendt at Penn State University Fruit Research
and Extension Center, PO Box 309, Biglerville, Pa 17307 has done a
lot of work with canola as a cover crop and green manure crop.
However, I'm pretty sure Dr. Halbrendt has not done any work with
strawberry. Especially as to annual production.
Colorado State Univ.
Rogers Mesa Research Center
3060 HWY 92
Hotchkiss, CO 81419
Phone: (970) 872-3387
fax: (970) 872-3397
! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !
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.
disclaimer: I wrote the brassica article for the IPMP referred to above.
I recently attended the USDA_ARS weed control field tour in Prosser,
Washington. The rapeseed variety Jupiter and the brown mustard variety
Green Wave both appeared fairly effective in controling weeds after
incorporation. Hope this helps.
This is in response to Karen's question about brassicas as a soil fumigant.
Last year I set up an experiment in a commercial pea field here in SW
Washington to investigate the pest control potential of several crops
planted as overwintering covercrops. I will say right off that my
experiment was washed down the river in 3 successive floods this spring.
Oh well - the trials and tribulations of on-farm research. But what I did
learn was some of the literature on the subject.
Excuse the ad nausium message. Just thought others might be interested in
the topic. I am always collecting information for future reference and
would appreciate hearing from others who are researching or following this
topic. This is an experiment which I hope to repeat in the near future.
Soil fumigants are expensive and in some cases being phased out. I think
we need to seriously investigate alternatives.
Managment of the cover crop is critical to the success of pest control.
Winter cover crops are fall planted and plowed down in the spring. Fall
planting should be timed so that the cover crop puts on enough growth
before winter, but not so much growth that flowering occurs before plow
down. Not only is excess vegetative growth difficult to plow down, but
also, the seed can become a weed.
Winter hardy plants are likely to be the most effective for pest control
because it is the decomposition of green plant material which gives these
plants their pesticidal properties. Correct me if I am wrong, anybody, but
I do not think that a dead plant when plowed down will produce the same
chemicals as decaying green tissue. I have not seen any tests of this,
just my opinion.
Planting of the successive crop should not occur within 2 weeks of plow
down - otherwise the crop will likely suffer the same fate as the pests.
The mode of action of these cover crops does not appear to be very
discriminatory. They likely affect beneficial organisms as well as
pathological ones. I do not know if any research has measured this, but it
is my understanding.
To enhance the action of the pesticidal crop, tarping is suggested - this
will prevent the active chemicals from being volatilized.
Weed control - small seeded weeds are the most likely to be controled due
to some penetration factor. I am sure this is related to seed coat and
uptake, but I do not have any results to quote.
Current research includes:
2 references from SARE/ACE report:
1. 1992. Rapeseed planted as a green manure in potatoes for control of
root-knot nematode. Control was up to 80%, yields were boosted 10-50%, and
weed biomass was reduced up to 50% - compared to standard pesticide plots,
I believe (not clearly stated in abstract). Project coordinator is Jeffrey
Stark, U. of Idaho, 208-397-4181.
2. 1992. European fodder radish as alternative to aldicarb (soil
fumigant) in sugarbeets for cyst nematode control. Infestation reduced
57%, yields boosted by 5 tons/A (30% greater than aldicarb-treated plots).
Radish acts as a trap crop. Project Coordinator is David Koch, U of
1994. Weed control with green manures and cover crops - white mustard,
rapeseed, annual rye, and sudangrass - in green pea, potato and mint.
Kassim Al-Khatib, WSU Mt Vernon Research Station, 360-424-6121. I do not
know if any results have been published yet.
Suppression of root-knot nematode populations with selected rapeseed
cultivars as green manure. H. Mojtahedi, et al. 1991. J of Nematology
Managing M. chitwoodi (Columbia root-know nematode) on potato with rapeseed
as green manure. H. Mojtahedi, et al. 1993. The American
Phytopathological Soc. 77(1):42-46.
Cover crops for root lesion nematode (P. penetrans) suppression. 1994(?),
Oregon Hort Society, Diane Kaufman & Russ Ingham, OSU.
Carol A. Miles, Ph.D.
Washington State University
Extension Agricultural Systems
360 NW North Street
Chehalis, WA 98532
PHONE 360-740-1295 FAX 360-740-2792
<Winter hardy plants are likely to be the most effective for pest control
<because it is the decomposition of green plant material which gives these
<plants their pesticidal properties. Correct me if I am wrong, anybody, but
<I do not think that a dead plant when plowed down will produce the same
<chemicals as decaying green tissue. I have not seen any tests of this,
<just my opinion.
If you looked at the plant pathology literature, you would find that
dried plant residues are just as effective. Indeed, dried cabbage
residues are excellent, and could be collected and moved to fields
where needed. The refs for this are in the IPM Practitioner article
mentioned in a previous post [which I sent once, but which the sanet-mg
server seems to be sending out endlessly, ad nausem].
RE your inquiry about a mustard crop alternative for methyl bromide
use, you might want to contact Dr. John Halbrendt at Penn. State's
Bigglerville Research Center. He has been working on that option for
several years. My recollection is that he has had good results with a
cv. named "Humus". The procedure was to grow the mustard and plow
it under while soil moisture levels were sufficient to facilitate
conversion of the naturally occuring glucosinilate (?) in the
mustard crop to methyl isothiocyanate (the active ingredient in the
no longer available fumigant, Vorlex). Anyway, John would be the
person to contact for details. Good luck.
Colo. St. Univ. - Orchard Mesa Research Center, Grand Junction, CO
Harold Larsen ph: 970-434-3264
Colo. St. Univ FAX: 970-434-1035
Orchard Mesa Research Center EMail: OMRC@coop.ext.colostate.edu
3168 B .5 Road
Grand Junction, CO 81503-9621
Some of the most extensive testing I know of was done by Jim Stapleton
out of the University of California. I don't recall whether he looked at
strawberries, but he tested the effect of a number of cover crops
(mustard etc) in a factorial experiment with solarization. I don't have
Jim's address right now, but he is in the Amer. Phytopath. Soc. as well
as U. C., I believe.
Check w/ Marvin Pritts <email@example.com> at Cornell regarding the crop
rotation for strawaberries. He used it w/ matted row system, northern
adapted varietes. If you get any useful information on alternatives to
methyl bromide could you please pass this information on to me?
North Carolina State University
207 Research Station Rd.
Plymouth, NC 27962
while this may be true we have had some problems with mustards such as
rapinni which seems to be a collector of insects of all types which is great
as long as that is not your crop i would be interested in seeing other
results for the mustards especially for fumigation .how wouldyou use the
mustards for this ?
Rt 19 Box 111-D
Santa Fe, NM 87505
505 988 3096
This letter was printed the other day in the Watsonville
Register-Pajaronian. It was written in response to several venomous
letters from the strawberry industry assailing a local teacher for teaching
about pesticides (methyl bromide) and getting her kids to write letters to
Feel free to use it in your endeavors.
June 1, 1996
P.O. Box 50055
Watsonville, CA 95077
To the editor,
I am writing to deliver some factual evidence to the debate on
Watsonville school children being educated about the hazards of pesticides.
Not only do the children of Watsonville have the right to learn the truth
about the health impacts of pesticide use in their communities, it is only
through such education that they can begin to protect themselves from harm
should they take jobs in the agricultural sector or live near farmland.
The truth is, the Watsonville area, according to data submitted to the
California Department of Pesticide Regulation by farmers themselves, has
some of the most intensive use of pesticides in the entire state and indeed
A new study published jointly by the University of California and
the state found that strawberries, a major Watsonville area crop, are by
far the most intense users of pesticides in California at 234 pounds of
pesticides per acre of berries. That equals almost 150,000 pounds per
square mile, to put it in more tangible terms. While the vast majority of
this total pesticide use is made up of the soil fumigants methyl bromide
and chloropicrin, over thirty different synthetic pesticides were used by
the strawberry farmers of Santa Cruz County last year. This same study
found that the use of pesticides has increased in recent years and that
state wide, pesticide use amounts to six pounds per capita. In Santa Cruz
County pesticide use totaled 1.5 million pounds in 1993, the last year for
which complete data are available. Pesticide use in Monterey County
totaled 8.2 million pounds that same year.
County records show that in 1995 growers used almost 633,000 pounds
of methyl bromide on 1,865 acres of Santa Cruz county farmland. Strawberry
fields accounted for at least 80 percent of this use (506,000 pounds). In
1992, the strawberry crop was the target of 61percent of all the pesticides
applied county wide ( including 98 percent of the Captan used (a Prop 65
listed carcinogen) and 79 percent of the Benomyl used (a Prop 65 listed
reproductive toxin). It is not an exaggeration to say that your area is
one of very heavy pesticide use, even for California.
However, even more important than the heavy use of pesticides is
the high potential for human illness from offsite drift of these
pesticides. Breathing methyl bromide for example is serious health threat.
Methyl bromide is a highly toxic gas and it never stays where it is put.
According to the latest studies, anywhere from 30-60 percent gets into the
air depending on the application method and weather, despite the plastic
tarping placed on top. Methyl bromide goes right through plastic. It
doesn't take a plastic glue failure, a strong wind or kids ripping off the
plastic for there to be methyl bromide in the air around strawberry fields.
Applications of methyl bromide to California strawberry fields average
around 200 pounds per acre. That means 60 to 120 pounds vaporizes into the
surrounding breathing space from each acre of strawberries.
The Department of Pesticide Regulation and the farmers know this.
But instead of monitoring how much methyl bromide is in the air, they use
computer models to guess where the methyl bromide will go after it leaves
the field and use this information to establish a "buffer zone" around
fields where methyl bromide is used. It is dangerous to enter this buffer
zone after a methyl bromide application. The DPR's methods of computer
modeling have been questioned by experts in the field of risk assessment.
As reported last February in the Los Angeles Times, the DPR is using an old
version of the computer model and using weak meteorological data averaged
statewide, instead of local weather data that gives a better picture of
where the methyl bromide will drift.
The scientist who developed these computer models while working for
the state (now a private consultant on air pollution) compared the DPR
buffer zones to more realistic buffer zones using an updated computer model
and local, up-to-date weather data. He found that in Salinas for example,
DPR buffer zones should be 4 to 10 times larger than currently mandated for
various field sizes and pesticide application rates. A DPR buffer zone of
40 feet should be 510 feet, A DPR buffer zone of 140 yards should be more
than a quarter mile. This raises serious questions about the safety of
people living, working and going to school close to methyl bromide treated
In testimony before the California Assembly in February, Dr.
William Pease, a toxicologist at UC Berkeley and the Environmental Defense
Fund, illuminated the health effects of methyl bromide as a nerve toxin, a
reproductive and developmental toxin, and went on to show that the state
has not established methyl bromide air pollution standards to protect
humans from chronic exposure to methyl bromide. Nobody is monitoring how
much is in the air and the methyl bromide levels that are legally allowed
in the air are derived from studies on rats and rabbits, even though
primates, including humans, have been shown to be more sensitive. The one
study that attempted to measure the chronic effects of low level exposure
ended with six dead beagles after just a few days. It was determined by
the researchers that "the cumulative effect for methyl bromide induced
neurotoxicity made it difficult to estimate an exposure level which the
dogs could tolerate for a 28-day or 1 year exposure study."
Methyl bromide is being used near people. Subdivisions and schools
are increasingly close to agricultural areas in California. An
Environmental Working Group (EWG) report completed in February found that
Santa Cruz county had three elementary schools and day care centers within
1.5 miles of over 25,000 pounds of methyl bromide use. Neighboring
Monterey County had 24 schools within the same range and 4 schools within 2
miles of more than 80,000 pounds of annual methyl bromide use. One of
these, the Ohlone elementary school, is literally surrounded by strawberry
farms, a pastoral but potentially dangerous setting.
In addition to methyl bromide, strawberry fields get their share of
toxic fungicide and insecticide treatments as well. A recent record of
pesticide applications during from March and April to a strawberry field in
Castroville reads like a hit list of noxious pesticides. This one field
was treated with multiple fungicides, insecticides and herbicides during
the two month period: three times with Captan, twice with benomyl
(Benlate), twice with iprodione (Rovral), once with metalaxyl (Ridomil),
five times with Malathion, once with glyphosate (Roundup), twice with
abamectin (agri-mek) and six times with sulfur along with several other
compounds. Benomyl, captan and iprodione are all classified by the EPA as
carcinogens. Malathion is a potent nervous system toxin.
It is hardly surprising that some of the pesticides that go onto
strawberries in the fields remain on the fruit when it gets to the
supermarket. An Environmental Working Group report, "The Shopper's Guide to
Pesticides in Produce", in which we analyzed FDA pesticide residue data, ,
found that when compared to 41 other fresh fruits and vegetables,
strawberries ranked worst for pesticide contamination. This report is
available on the World Wide Web at www.ewg.org.
The facts speak for themselves and should not be obscured by those
condemning the Watsonville teacher for using the classroom to convey
"political" beliefs. There is nothing political about the right-to know.
And one more thing, it is worth noting that Teresa Thorne, who penned a
recent sharply worded letter to the Pajaronian assailing the teacher and
public schools generally as havens for misinformation, failed to mention
that she is an employee of the California Strawberry Commission.
It is not surprising that the strawberry industry was the first to
condemn the discussion of pesticides in Watsonville schools. Knowledge is
a powerful thing.
Environmental Working Group
Kert Davies ENVIRONMENTAL WORKING GROUP
1718 Connecticut Ave. NW, Suite 600
Washington, D.C. 20009
EWG web page: http://www.ewg.org
202-667-6982 fax 202-232-2592
Any opinions expressed are mine and not my employer's.