  SEQ CHAPTER \h \r 1 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

									OFFICE OF

PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES

MEMORANDUM

SUBJECT:	Assessment of the Benefits of Chloropicrin, Methyl Bromide,
Metam-sodium and Dazomet Use In Strawberry Nursery Runner Production 

FROM: 	Leonard Yourman, Plant Pathologist

		Biological Analysis Branch

		Stephen Smearman, Economist

		Economic Analysis Branch

THRU:	Arnet Jones, Chief

		Biological Analysis Branch

		Biological and Economic Analysis Division (7503P)

Timothy Kiely, Chief

		Economic Analysis Branch

		Biological and Economic Analysis Division (7503P)

TO:		John Leahy, Senior Policy Advisor

		Special Review and Reregistration Division (7508P)

Summary

This document presents the assessment of the benefits provided by soil
fumigants in the production of strawberry plants.  Methyl bromide is the
fumigant of choice in strawberry nursery plant production in California
and the southeastern U.S. (primarily North Carolina).  Pest-free
requirements by state regulations for nursery stock must be considered
by nursery managers.  The alternative to methyl bromide is
1,3-dichloropropene (1,3-D) plus chloropicrin used for pathogen (crown
rot and black root rot) and nematode control, and a follow-up treatment
of metam-sodium or dazomet for weed management.  However, certification
for pest-free designation of nursery stock requires a soil treatment
that will result in certification of nursery stock (CDFA, 2003).  The
benefits of using methyl bromide can result in yields that are 10%
greater than yields using treatments of 1,3-D plus chloropicrin on per
acre basis under certain soil conditions where there exists soil with a
high moisture content.  

Fumigation of soils for nursery stock is necessary to attain pest-free
certification, without which, nursery stock plants are unmarketable. 
All California strawberry growers rely on fumigation to provide
pest-free nursery stock (approximately 1 billion plants per year are
produced in California).  

The total national net revenue benefits associated with methyl bromide
are estimated to be $13.2 million for nursery stock if growers were to
switch from 1,3-D plus chloropicrin to methyl bromide.

	

Introduction

As part of the reregistration process, EPA is assessing the benefits of
the use of several soil fumigants: dazomet, chloropicrin, metam
potassium, metam sodium, and methyl bromide (MeBr).  This document
presents the assessment of the benefits provided by soil fumigants in
the production of strawberry plants.  Some of the benefits of soil
fumigants are the improvements in production by reducing pest pressure
(Table 1) and/or reductions in costs resulting from the use of the
fumigant.  The social benefits of a pesticide are divided between the
users of the pesticide, such as strawberry nursery managers, and
consumers of the commodity.  Consumers benefit because higher production
and/or lower costs translate into a cheaper and more abundant supply of
goods.

STRAWBERRY PLANT NURSERIES

California.  California is the world’s major producer of strawberry
plants with an annual production of nearly a billion plants on
approximately 4,000 acres (Norton, 2000).  Plants for field production
are grown in nurseries by asexually propagating rooting runners from
source plants.  The California strawberry nursery industry provides
genetically clean planting material to strawberry fruit growers and
other nursery systems.  Strawberry nurseries annually plant source
stocks in fumigated fields, root the runners that form, and harvest
these runner plants as a final product.  Key pests associated with soils
for strawberry nurseries are identified in Table 1.

California nurseries produce their transplants over a five-year cycle,
transferring plants between low and high elevation nurseries (CUN, 2007;
CUN, 2006).  Screenhouses are used during the first two years and open
field plantings are used during the last three years.  Methyl bromide is
used to treat field soils.  Individual sites are planted to strawberries
once every three years.  The fourth and fifth production years account
for 22% and 77%, respectively, of the current methyl bromide nursery
usage in California.  Transplants produced are distributed widely
throughout the U.S. and other countries.  

Strawberry runners are grown in a complex production system (Table 2). 
A typical nursery system includes both high- and low-elevation nursery
locations, chosen to provide a cold site for October harvest, which
provides fresh plants for fruit production systems, and a warmer site
for December-January harvest, which provides frigo (dormant, cold-stored
) plants for nursery stock and fruit production systems.  

The high elevation nurseries are located in Northern California and
Southern Oregon at elevations of 3,200 to 4,200 feet.  They produce
plants used in October and November plantings for fruit production in
California.

Low elevation nurseries (below 600 feet) are located in the Sacramento
and northern San Joaquin valleys of California.  These low elevation
nurseries produce plants for both propagation and fruit plantings.  The
propagation stock is used by nurseries in California, throughout the
United States, and internationally.  The balance of the low elevation
production is stored for distribution through the spring and summer
months as frigo plants.

Southeastern U.S.  Southeastern U.S. nurseries (primarily in North
Carolina) produce transplants in open fields.  An individual field is
planted to strawberries once every three years (Table 2).  Approximately
85% of transplants produced are sent to Florida (CUN, 2007).  Nurseries
in this region range in area from 3 to 80 acres with three of the
largest nurseries averaging 50 acres and representing 71% of nursery
land area (CUN, 2007).  The typical yield for this region is 200,000
plants per acre.  For the critical use exemption use of methyl bromide,
the Southeastern Strawberry Nursery Consortium requested methyl bromide
to be used on 209 acres for the 2009 use season to manage key soil pests
(Table 1).

Table 1.  Target pests for fumigants for strawberry runner production.

State	Key Pests

California	Diseases: Phytophthora Crown and Root Rots (Phytophthora
spp.); 

Red Stele (Phytophthora fragariae); Verticillium Wilt (Verticillium
dahliae); Anthracnose (Colletotrichum acutatum)

Nematodes: Root-knot (Meloidogyne spp.); 

sting (Belonolaimus spp.); 

dagger (Xiphinema spp.); 

lesion (Pratylenchus spp.); 

foliar (Aphelenchoides spp.); 

needle (Longidorus spp.); 

stem (Ditylenchus spp.)

Weeds: numerous weeds listed (e.g., annual bluegrass, bur clover,
carpetweed, chickweed, field bindweed, goat grass, hairy nightshade,
lambsquarter, malva, nutsedge, pig weed, portulaca, prostate spurge,
puncture vine, purslane, vetch)

Southeastern U.S.	Diseases: Black root rot (Rhizoctonia and Pythium
spp.) (100%); Crown rot (Phytophthora cactorum) (<5%)

Nematodes: root-knot nematodes (Meloidogyne spp.) (100%)

Weeds: Yellow nutsedge (Cyperus esculentus) and Purple nutsedge (Cyperus
rotundus) (50%)

*Source: CUN, 2007; CUN, 2006.

Certification issues for nurseries.  Nurseries providing strawberry
plants for propagation or for fruit production are required to receive
certification of pest-free status.  Certification requirements are
strict and regulations include fumigation standards, as well as
standards for viruses, pathogens, nematodes, and insect control.  For
example, “When nursery stock in the nursery is found by the inspector
to be infested with any plant pest, the certificate may not be issued
until the infested stock has been treated or destroyed to the extent
that the salable stock to be covered by the certificate shall be
apparently free of plant pests” (NCDA, undated).  

Strawberry nurseries are required to produce pest-free plants to meet
certification (e.g., CDFA, 2003; NCDA, undated) and quality standards. 
There are no markets for runners that do not meet the certification
standards.  The failure to adequately manage pests in transplants will
jeopardize overall fruit production.  As the use of methyl bromide is
phased-out in accordance with the Montreal Protocols, alternatives are
being studied as replacements.  Currently, all strawberry nursery soils
are treated with methyl bromide + chloropicrin to manage key pests for
certification requirements.  

According to California nursery regulations (CDFA, 2003) for field-grown
nursery stock, the acceptable chemical fumigants for nematode control
are methyl bromide and 1,3-D.  Container-grown stock may also be treated
with steam or solarization if appropriate conditions for killing
nematodes are met.  The first two years of the five year production of
nursery plants occurs in screenhouses (in California).  However, soil
treatments are required for the final three years of field growth (see
Appendix 1).



Table 2.  Characteristics of nursery cropping systems.

CHARACTERISTICS 	Region 

	Southeastern U.S.	California*

Crop type	Strawberry transplants	Strawberry transplants

Annual Crop 	Annual crop, replanted in same site once every three years
Annual crop, only planted in the same location once every three years

Typica Typical crop rotation 	Various crops planted	The principal
rotational crops are grains, or fallow, for two years.  Usually,
incorporated for increased organic matter.  May also include, endive,
garlic, onions, horseradish, and mint.

Soil texture	93% loam and 7% sandy soils, containing up to 2% organic
matter	80% sandy soils, 10% loam soils and 10% clay soils; 70% with 2%
or less organic matter

Typical dates of planting and harvest 	Plant: April/May

Harvest: Sept/Oct	Low elevation: Planting: May/June

Harvest: January 

High elevation:

Planting: April

Harvest: Sept-Nov

Typical dates of fumigation	Sept/Oct	April (low elevation); Aug/Sept
(high elevation)

Frequency of fumigation	Once in three years 	Prior to planting on
different fields (high and low elevation nurseries)

USDA Plant Hardiness Zones	6a, 6b, 7a, 7b, 8a, 8b	6a, 6b, 7a, 9a, 9b

Source: CUN, 2007; CUN, 2006

Fumigants for Strawberry Nurseries

Methyl Bromide 

California.  Currently all nurseries use methyl bromide for plant
production (including those plants destined for organic fruit
production).  Fumigation is necessary for nematode-free certification. 
In addition, methyl bromide also manages other pests such as soil-borne
pathogens and weeds.  Methyl bromide is shank injected 25-30 cm below
the soil surface, mostly broadcast; always mixed with chloropicrin. 
Research is being conducted to find acceptable alternatives that will
allow certification of nursery stock (e.g., Kabir et al., 2003, 2005). 
California considers 99% of nursery runners produced in the state as
eligible for quarantine and pre-shipment use of methyl bromide (for 2009
use season, 1.1 million lb of methyl bromide were requested to treat
4,600 acres (CUN, 2007).

Southeastern U.S.  Currently, all nurseries in this region use methyl
bromide + chloropicrin, which is shank injected 30-45 cm below the soil
surface.  It is broadcast (50%) or strip fumigated (on 55% of a total
acre).  

Chloropicrin.

California.  Certification guidelines do not list chloropicrin as a
“stand-alone” treatment for certification.  Chloropicrin is always
used with methyl bromide for nursery soils, currently at a ratio of
methyl bromide to chloropicrin ranging from 67:33 to 50:50, depending on
the pest situation and soil conditions.  Chloropicrin is an effective
fungicide, but generally does not adequately control nematodes or weeds.
 Verticillium wilt is a major problem for strawberry growers and
disease-free plants are required so the pathogen is not further
distributed.  Chloropicrin is the more active fumigant against
Verticillium wilt when methyl bromide + chloropicrin or 1,3-D +
choropicrin are applied.  In addition, high rates of chloropicrin are
restricted in some counties in California.  Research (e.g., Kabir et
al., 2005) is ongoing to study alternatives to methyl bromide. 
Currently, California lists only methyl bromide and 1,3-D as acceptable
chemical fumigants.  

Southeastern U.S.  Certification guidelines do not list chloropicrin as
a treatment for certification.  Currently nurseries always use methyl
bromide + chloropicrin.  The currently used ratio of methyl bromide to
chloropicrin for this region’s nurseries is 67:33.  While chloropicrin
is an effective fungicide, weed problems in this region usually require
additional chemical treatments.

1,3-Dichloropropene (1,3-D). 

California.  Methyl bromide and 1,3-D are the only chemical fumigants
eligible for treating open field nursery soils for certification (CDPR,
2003).  Township caps may restrict the use of 1,3-D (Trout, 2005). 
Results of research trials (e.g., Kabir et al., 2003, 2005) showed that
1,3-D + 35% chloropicrin (Telone C-35) that is shank injected may be an
effective alternative to methyl bromide.  The 1,3-D + chloropicrin
treatment may be followed by an application of dazomet to reduce weed
populations.  The use of 1,3-D without chloropicrin is generally not
considered a broad spectrum treatment for strawberry nursery
requirements.  

Southeastern U.S.  Information is being requested to determine if 1,3-D
is allowed for nursery stock certification and, if so, under what
conditions.  Weed problems in this region will likely require additional
treatments with herbicides for less than optimal fumigation products.

Metam-sodium, dazomet (and other methyl
isothiocyanate—MITC—producers).  

California.  These compounds are generally not effective as “stand
alone” products for nursery plant production.  Field trials in
California suggest using dazomet following 1,3-D, iodomethane, or
chloropicrin (e.g., Kabir et al., 2005) to maximize weed control.  

Southeastern U.S.  These products are not alternatives to methyl
bromide.  Follow-up applications after 1,3-D + chloropicrin in research
studies (as have been done in California) are being conducted. 
Restrictions on the use of 1,3-D would limit the usefulness of MITC
products.

Estimated Benefits of Methyl Bromide

To determine the economic benefits of methyl bromide, BEAD used a
partial budget analysis to estimate the changes in production costs on a
typical acre for strawberry nursery crop grown.  This approach allows
the Agency to compare changes to net operating revenue.  Net revenue is
calculated as gross revenue minus operating costs.  This is a good
measure of the direct changes in the income that may be realized by
growers currently using methyl bromide for pest control.  Net revenue
does not represent net income to the users.  Net income, which indicates
profitability of an operation of an enterprise, is gross revenue minus
the sum of operating and fixed costs.  Net income should be smaller than
the net revenue measured in this study.  Fixed costs were not included
because they are often difficult to measure and verify. 

While this is a discussion of the benefits of all fumigants for
strawberry nursery producers, the primary fumigant used by producers in
California and Florida is MeBr.  Therefore the baseline established to
determine the benefits of all potential fumigants is based on using MeBr
and comparing the costs and revenues of growers who use MeBr to the
estimated changes in costs and revenues that may be realized using
another fumigant such as 1,3-D plus chloropicrin which is presented
here.

Per Acre Regional Benefits - California  

In California, MeBr is the primary fumigant used by strawberry growers
with 1,3-D plus chloropicrin as a second choice for many. If growers us
an alternative other than MeBr, a yield losses of approximately 10% are
expected (California Strawberry Commission CUE request).  If growers
choose 1,3-D plus chloropicrin to control pathogens and nematodes,
control costs are expected to increase from $731 to $1,932 per acre, an
increase of $1,201 per acre or 164 %.  Net operating revenue is expected
to drop from the methyl bromide baseline of $4,807 to $1,626 per acre, a
decrease of $3,181 per acre or a 66% decrease.  This is due to both
yield losses and the increase in control costs and harvesting costs.  

The benefits associated with methyl bromide for California strawberry
nursery stock production are illustrated below in Table 3.  Total
California production losses are based on California Department of
Pesticide Regulation data for the 4,000 acres treated with methyl
bromide.  The estimated regional loss is estimated to be $12.7 million
for 1,3-D plus chloropicrin.

Table 3.  Estimated Per Acre Gross Revenue, Operating Costs, and Net
Operating Revenue Impacts for California Strawberry Nursery Production

	Baseline

Methyl Bromide	Alternative

1,3-D + Pic	% Change

Yield (boxes/acre)	332	299	-10

Price  ($/lb)	50	50

	Gross Revenue  ($/box)	16,600	14,940	-10

Methyl bromide

1,3-D + Pic ($/acre)	731

	

1,932	

164

Other Operating Costs  ($/acre)	4,187	4,187

	Harvest Costs  ($/acre)	6,875	7,195	5

Total Operating Costs  ($/acre)	11,793	13,314	12

Net Operating Revenue  ($/acre)	4,807	1,626	-66

Source:  USDA NASS (2006), 2006 Methyl Bromide Critical Use Nomination
for Preplant Soil Use on Strawberry, BEAD calculations.  Assumptions: 1:
fumigation costs include tarp and hand weeding costs; Figures may not
sum due to rounding.

Per Acre Regional Benefits - Southeastern  

Without the use of methyl bromide, Southeastern strawberry nursery stock
producers are likely to experience yield losses of 10%.  If growers
choose 1,3-D plus chloropicrin to control pathogens and nematodes,
control costs are expected to increase from $1,418 per acre to $1,932
per acre, an increase of $514 per acre or 36%.  Net operating revenue is
expected to drop from the methyl bromide baseline of $4,760 to $2,546
per acre, a 47% decrease due to yield losses and increases in control
costs. 

Total Florida production losses are based on USDA NASS 2004 data
estimates for the estimated 209 acres treated with methyl bromide.  The
regional loss is estimated to be $462,726 if 1,3-D plus chloropicrin is
used to replace methyl bromide.

The impacts associated with the loss of methyl bromide as the baseline
for Southeastern nursery stock production are illustrated below in Table
4.

Table 4.  Estimated Per Acre Gross Revenue, Operating Costs, and Net
Operating Revenue Impacts for Southeastern (North Carolina) Strawberry
Nursery Production

	Baseline

metam sodium	Alternative

1,3-D + Pic	% Change

Yield (plants/acre)	188,888	169,999	-10

Price  ($/plant)	0.09	0.09

	Gross Revenue  ($/acre)	17,000	15,299	-10

Methyl bromide ($/acre)

1,3-D + pic ($/acre)	1,418	

1,932	

36

Other Operating Costs  ($/acre)	6,222	6,221	<1

Harvest Costs  ($/acre)	4,600	4,600

	Total Operating Costs  ($/acre)	12,240	12,753	4

Net Operating Revenue  ($/acre)	4,760	2,546	-47

Source: USDA NASS (2006), 2006 Methyl Bromide Critical Use Nomination
for Preplant Soil Use on Strawberry, BEAD calculations.  Assumptions: 1:
fumigation costs include tarp and hand weeding costs; Figures may not
sum due to rounding.

 

National Benefits

Total national net revenue impacts associated with the loss of methyl
bromide are estimated to be $13.2 million for acres treated with 1,3-D
plus chloropicrin as an alternative to methyl bromide.  

Conclusion

Fumigants for strawberry nurseries are necessary to provide pest-free
stock plants to strawberry fruit producers.  Transporting diseased
plants to growers would have a devastating effect on the strawberry
industry.  Currently, methyl bromide + chloropicrin is used by all
strawberry nurseries located in California and the southeastern U.S. 
Without methyl bromide, nurseries would likely use 1,3-D + chloropicrin,
with a possible follow-up treatment of metam-sodium (or similar
fumigant).  Nurseries must be able to have their stock plants certified
as pest-free by state regulators in order to have marketable plants for
use by farmers.

References 

CDFA (California Department of Food and Agriculture). 2003. Summary of
California Laws and Regulations Pertaining to Nursery Stock.   
HYPERLINK "http://www.cdfa.ca.gov/phpps/pe/nipm.htm" 
http://www.cdfa.ca.gov/phpps/pe/nipm.htm ;   HYPERLINK
"http://www.cdfa.ca.gov/phpps/pe/nipm_pdfs/nipm_7.pdf" 
http://www.cdfa.ca.gov/phpps/pe/nipm_pdfs/nipm_7.pdf 

CUN (Critical Use Nomination) for Methyl Bromide Use for Strawberry
Nursery Stock Grown In Open Fields. 2006.
onhttp://www.epa.gov/spdpublc/mbr/CUN2008/CUN2008_StrawberryNursery.pdf

CUN (Critical Use Nomination) for Methyl Bromide Use for Strawberry
Nursery Stock Grown In Open Fields. 2007.
http://www.epa.gov/spdpublc/mbr/cun2009/cun2009_StrawberryNursery.pdf

Kabir, Z., Fennimore, S., Martin, F., Ajwa, H., Duniway, J., Browne, G.,
Winterbottom, C., Westerdahl, B., Goodhue, R., Guerrero, L., and Haar,
M. 2003. Alternative[s] Fumigants for the Control of Soil Pests:
Strawberry as a Model System. Annual International Research Conference
on Methyl Bromide Alternatives and Emissions Reductions. www.mbao.org.

Kabir, Z., Fennimore, S. A., Duniway, J. M., Martin, F. N., Browne, G.
T., Winterbottom, C. Q., Ajwa, H. A., Westerdahl, B. B., Goodhue, R. E.,
and Haar, M. J. 2005. Alternatives to methyl bromide for strawberry
runner plant production. HortScience 40(6):1709-1715.

Messenger, B. and Braun, A. 2000. Alternatives to methyl bromide for the
control of soil-borne diseases and pests in California.  Pest Management
and Analysis Planning Program.
http://www.cdpr.ca.gov/docs/dprdocs/methbrom/alt-anal/sept2000.pdf

NCDA (North Carolina Department of Agriculture and Consumer Services),
undated.  Nursery Regulations, Nursery Certification.   HYPERLINK
"http://www.ncagr.com/plantind/Regs/48a1200.htm" 
http://www.ncagr.com/plantind/Regs/48a1200.htm , 

  HYPERLINK
"http://reports.oah.state.nc.us/ncac/title%2002%20-%20agriculture%20and%
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Norton, J. 2000. Pest management evaluation for California strawberry
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http://www.cdpr.ca.gov/docs/empm/alliance/99-00/evals/99-0192.pdf

Trout, T. 2005. Impact of township caps on telone use in California.
Annual International Research Conference on Methyl Bromide Alternatives
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"http://www.mbao.org/2005/05Proceedings/127TroutT%20mb-pest-use-telone-r
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http://www.mbao.org/2005/05Proceedings/127TroutT%20mb-pest-use-telone-rp
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