  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 Soil Fumigants (Methyl Bromide,
Chloropicrin, Metam-Sodium, Dazomet) Used by Forest Tree Seedling
Nurseries

FROM:	John Faulkner, Economist

		Economic Analysis Branch

		Leonard Yourman, Plant Pathologist

		Biological Analysis Branch

		Biological and Economic Analysis Division (7503P)

THRU:	Timothy Kiely, Chief

		Economic Analysis Branch

		Arnet Jones, Chief 

		Biological Analysis Branch 

		Biological and Economic Analysis Division (7503P)

TO:		Special Review and Reregistration Division 

PRODUCT REVIEW PANEL DATE:  April 11, 2007

Summary

This assessment focuses on the benefits of fumigants to forest seedling
nurseries.  Methyl bromide and chloropicrin are important to forest
seedling nurseries in order to satisfy demand for tree seedlings to
reforest land and provide forests for fiber, wildlife and conservation
purposes.  Without the use of methyl bromide and chloropicrin, yield
losses would likely be 5% or greater and production costs would be
higher.  In addition, seedling quality would be compromised resulting in
slower growing trees, greater yield loss if the poor quality seedlings
are rejected, and the spreading of pathogens, weeds, and other pests to
forests, if the seedlings are contaminated with such pests.  Maintaining
pest-free nursery soils is critical to producing healthy seedlings and
the foundation for establishing economically viable forest land. 
Billions of tree seedlings are produced in tree nurseries throughout the
U.S. and provide benefits far beyond the nurseries themselves, but
transfer to the millions of acres of forests that depend on healthy
seedlings for the establishment of healthy forests.

Introduction—Production Practices of Forest Seedling Nurseries

Forest seedling nurseries in the U.S. supply conifer and hardwood
seedlings that are used for reforestation, forest establishment, fiber
production, and wildlife and conservation uses.  The impact of seedling
quality and size on the success of forest establishment cannot be
overstated. The quality of seedlings is highly correlated with the
success of the regeneration process and corresponding long-term economic
and use benefits, where seedling quality results in greater survival
rates and faster growth.  Maintaining pest-free nursery soils is
critical to producing healthy seedlings and the foundation for
establishing economically viable forests. 

In a survey conducted in 2001-2002 by the Southern Forest Nursery
Management Cooperative, there were nearly 2 billion pine seedlings
produced by nurseries in the southern U.S. alone.  This accounted for
80% of U. S. pine seedling production.  Nurseries in the U.S. are
located in eight climate zones (USDA Zones 3 to 10) and have mostly
light or medium soils.  The majority of seedlings are species of
conifers, especially pine.  In addition, 30-60 species of hardwoods,
such as oaks, hickory, poplars, and ash, are produced.  Nurseries
produce seedlings adapted to their respective regional conditions, with
variables such as climate, elevation, and soil type. 

Some forest tree nurseries include those owned and managed by commercial
forest companies, such as Weyerhaeuser and International Paper.  These
nurseries typically are 100-400 acres in size, with fumigation and new
plantings occurring on one-quarter to one-third of the acreage during a
growing season.  Other nurseries owned by federal, state, or private
concerns range in size from fewer than 25 acres to 100 acres.

Conifer seedlings are typically grown for one or two years in seedling
beds.  Managers typically fumigate a particular conifer seedling bed
with methyl bromide once every 3-4 years, i.e., one-quarter to one-third
of the total nursery land is fumigated each year to produce two or three
harvestable forest seedling crops per single bed fumigation.  Typically,
a one- or two-year fallow or cover crop period occurs, followed by
fumigation.  Effective fumigants, such as methyl bromide, permit less
frequent bed fumigation per harvestable seedling crop.  For hardwood
seedlings, beds are fumigated prior to each seedling crop, as hardwood
species are generally more prone to root rots and damping-off diseases
than conifers, although the production volume of hardwoods is smaller
than overall conifer production.

At the appropriate stage of maturity, forest seedlings are harvested in
the nursery, packaged, and transported to the planting site.  Seedlings
are usually culled or sized during the harvesting process, with culled
trees discarded.  Large nurseries grade their seedlings and may sell
lower grade (#2) seedlings at a reduced price, or discard all but the
highest grade (#1) seedlings.  

In the southern U.S. approximately 50% of forest tree nurseries are
treated with methyl bromide (1620 acres out of 3250 acres of nurseries).
 Methyl bromide is particularly effective where high nutsedge
populations are endemic.  In southern nurseries, bareroot production
includes pine (91-96% of production) and hardwood species (4-9% of
production).  

In northeast nurseries production includes conifers (10-15 spp.), grown
for 1 year (8% of production), for 2 years (4%) and 3 years (14% of
production).  Hardwoods grown include 30-50 species with one-year old
plants (55% of production) and 2-year old plants (9% of production). 
Shrubs and forbs (>75 species) occupy 10% of production.

Target Pests for Fumigants

For many nurseries only #1 grade seedlings are sold or planted, #2 grade
and cull seedlings may be discarded and, therefore, overall production
can be reduced.  Fumigation is relied on to manage pests that interfere
with the growth of healthy seedlings.  Pests include fungal (e.g.,
Phytophthora, Pythium), nematodes (e.g., Criconemoides,
Helicotylenchus), and yellow and purple nutsedges (Cyperus spp.) (Cram
and Fraedrich, 1997).  Nutsedges are generally considered among the
major pests of forest seedling nurseries, and are a particular problem
in the southeastern U.S. and the pests most difficult to manage.  Table
1 indicates the key pests targeted by fumigants for forest seedling
nurseries in major production regions.

Table 1.  Target pests for fumigants in soils of forest seedling
nurseries.

Region	Key Pests

Southeast1	Weed: Nutsedge (Cyperus spp.); Pathogens: Fusarium, Pythium,
Rhizoctonia; Nematodes: Criconemoides, Helicotylenchus

Northeast2	Fungi: Phytophthora (damping-off, root rot), Fusarium
(damping-off, root rot), Cylindrocladium;

Weeds: Cyperus (yellow nutsedge) [40%], Cirsium (Canada thistle) [70%]

West3	Pathogens: Fusarium, Pythium, Phytophthora, Cylindrocarpon, Phoma;
Weeds: Cyperus (yellow nutsedge)

1 Includes: Alabama, Arkansas, Georgia, Louisiana, Mississippi, North
Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia

2 Includes: Illinois, Indiana, Kentucky, Maryland, Michigan, Missouri,
New Jersey, Ohio, Pennsylvania, West Virginia, Wisconsin

3 Includes: Washington, Oregon

Pest-free Designation

Nurseries providing seedlings for reforestation and other purposes must
ensure the planting of high quality, disease-free stock.  Depending on
regional regulations government certification requirements may (e.g.,
CDFA, 2003; NCDA, undated) or may not apply.  Regardless, zero tolerance
for damaging diseases and plant-parasitic nematodes apply for internal
quality control and grading requirements are implemented in order to
minimize the prospect of spreading nematodes and diseases from state to
state.  

Fumigants Used Forest Seedling Nurseries 

The fumigants used by tree nurseries are methyl bromide (under a
critical use exemption) + chloropicrin, chloropicrin,
1,3-dichloropropene (1,3-D) + chloropicrin, 1,3-D + chloropicrin +
metam-sodium, 1,3-D + metam-sodium, and dazomet as a follow-up
application to 1,3-D + chloropicrin or chloropicrin.  

Methyl bromide (used with chloropicrin in a formulation ranging from
67-98% methyl bromide) has been the standard fumigant for forest
seedling nurseries.  As the phase-out of methyl bromide continues,
research is ongoing to identify other effective fumigants. 
Inconsistency in pest management performance by alternatives where pest
pressure is high has been the primary reason that methyl bromide is
currently used with a critical use exemption label.  A fumigant at one
location may be an acceptable alternative, while at another location it
may not be (James et al., 2001).  While direct yield losses, in terms of
seedlings/hectare, may not be large on average, intensive seedling
production relies on the ability of nursery managers to meet quality, as
well as yield, goals.  In addition, economic issues such as increased
application costs (e.g., costs associated with application of
metam-sodium and a separate chloropicrin application) may have an impact
on overall feasibility of these alternatives for the forest seedlings
sector.

The use rates and characteristics of fumigants used in forest tree
nurseries are listed below:

Methyl bromide (350 lb/acre) + chloropicrin (7 lb/acre)

In general, a 98:2 ratio of methyl bromide:chloropicrin is used in some
eastern (north and south) nurseries due to high populations of weeds
(most importantly, nutsedge).  Conifer beds are generally fumigated once
in 3-4 years, beds growing hardwoods may be fumigated every year.

Methyl bromide (236 lb/acre) + chloropicrin (116 lb/acre)

In general, a 67:33 ratio of methyl bromide:chloropicrin is used where
weed problems may be less severe, and where disease problems are more
damaging.  This may be the situation in many nurseries in the western
U.S.  Pest problems, however, can be highly variable throughout the U.S.
even between locations in close proximity.

Historically, methyl bromide + chloropicrin is broadcast and shanked-in
at 350 lbs/ac.  After application the land is tarped (Masters, 2007).  A
total of approximately 500 acres of bareroot nurseries require
fumigation, with 42% of those acres treated per year.  An average of 20
acres is treated per day.  The formulation is generally 67% methyl
bromide, 33% chloropicrin, but 50-50% formulation may be as effective. 
Seventy percent (70%) of the soil fumigation is conducted in the late
summer on land that is in fallow.  Since the plantback is 5-6 months
later, the only urgency to remove the tarp is unexpected rainfall that
can make tarp removal difficult.  Thirty percent of all fumigation
occurs in the spring when soils are wet, and soil temperatures are cool,
preventing the use of methyl isothiocyanate (MITC) agents, such as
metam-sodium and dazomet.  Although this is not the optimal time of the
year to fumigate, high pathogen loads in some situations make it
necessary.  The only effective treatment at this time of the year is
methyl bromide + chloropicrin.  Based on these weather conditions and
limited plantback window, lower formulations of chloropicrin are used.

Chloropicrin (300 lb/acre)

Chloropicrin is an effective fungicide, but may not be effective against
high weed pressure (Carey, 2000; Carey, 1996; Enebak et al., 1990). 
Chloropicrin is an essential component of methyl bromide fumigation and,
when used at 100% active ingredient, has been tested by nurseries as an
alternative to methyl bromide (Enebak, personal communication, 2007). 
It is typically used with methyl bromide in formulations that contain
between 2% and 50% chloropicrin, with 2% and 33% being the most common. 
The decision to use a higher component of chloropicrin with methyl
bromide is generally a decision based on pest pressure.  Beds with high
weed populations usually demand higher amounts of methyl bromide, while
high pathogen populations require higher amounts of chloropicrin. 

Dazomet (356 lb/acre) or Metam-sodium (432 lb/acre)

These MITC producers may become alternatives to methyl bromide in some
nurseries, especially when used with chloropicrin.  They can be
effective against pathogens and weeds if soil conditions (soil texture
and moisture) are amenable.  If nematodes are present in high numbers,
these compounds would likely be used with the nematicide
1,3-dichloropropene.

Metam-sodium and dazomet have shown inconsistent results in managing
weeds, especially with moderate to high weed pressure.  They do not
consistently provide acceptable levels of nutsedge control, nor do they
effectively manage some important fungal pathogens (root rot and
damping-off pathogens).  This is a major reason that methyl bromide
continues to be a choice fumigant for this industry.  

Metam-sodium is generally incorporated with other chemicals, which may
add expense and increased fumigation.  For use in nurseries, application
of metam-sodium will be followed by tarping to avoid killing seedlings
in adjacent beds.  Field trials show that seedling size (diameter and
height) and root volume were inconsistent, non-uniform, and reduced with
dazomet, leading to higher counts of Grade #2 seedlings and culls
compared to greater numbers of Grade #1 seedlings with methyl bromide. 
Reduced efficacy requires production cycle compensation by increasing
the frequency of fumigation or lengthening the fallow period in order to
obtain better control of weeds and other pests.  These strategies result
in reduced seedling production.  Soil temperature requirements (above
4-6° C/ optimal 12-18° C) of dazomet or metam-sodium constrain their
use in some areas (north and west) Landis and Campbell, 1989; Fraedrich
and Dwinell, 2003; Carey, 1996; Carey, 1994; Enebak et al., 1990;
Darrow, personal communication, 2002).  A recent study found that
dazomet resulted in reduced seedling growth (Enebak et al., 2006).

Metam-sodium (432 lb/acre) + chloropicrin (102 lb/acre)

This treatment can be effective against weeds and fungi, especially with
low to moderate pressure and light soils (Carey, 2000; Carey, 1996;
Carey, 1994).  The application of metam sodium + chloropicrin involves a
three-step process, application of metam-sodium, then injecting
chloropicrin, and finally, application of the tarp (Enebak, personal
communication, 2005).  According to extension specialists in Alabama,
the incorporation of metam sodium using a rotovator is a slow process,
and the area to be treated within a given treatment window (determined
by weather: temperature, moisture, wind) is limited.  This window of
application is generally 4-6 weeks, and under the best application
methods, this treatment may take four times as long to apply as the
typical methyl bromide treatment.  Therefore, to treat the necessary
acres each year requires a four-fold increase in labor and additional
available equipment in order to apply metam-sodium, chloropicrin and
tarp.  According to the label, and depending on soil and weather
conditions, there would be a two to six week delay before planting after
application of metam-sodium, chloropicrin and tarp-covering.  This can
affect market production costs.  

The equipment needed to treat the area in spring and fall may not be
available without the purchase of additional applicator units.  This may
increase the cost to growers, as would the “set-up” time for the
treatment with additional machinery.  In order for tarps to be placed on
the treated metam-sodium areas, workers must return into the treated
area to lay down tarps after chloropicrin has been injected into the
soil.  In this case, out-gassing occurs, and workers must wear personal
protection equipment that is not desirable given the temperatures that
normally occur at the time of application.

1,3-D (232 lb/acre) + chloropicrin (125 lb/acre)

This combination is effective against nematodes and plant pathogens and
against moderate weed infestation.  It is most effective in sandy-type
soils with optimal moisture content.  It may not be effective against
high nutsedge pressure (Carey, 1996; Carey, 1994).  Chloropicrin is a
key component since 1,3-D alone is not an effective fungicide or
herbicide.

Non-Chemical Production

Container-grown tree seedlings are produced in a limited capacity
throughout the forest nursery industry.  One Michigan grower produces
greenhouse-grown plug plants, which are grown for 1-2 years, then
planted in beds for an additional 1-3 years.  Containers can also be
used for special circumstances where species survival or a genetic value
of the planting stock makes them economically feasible.  Recent surveys
indicate that of the 1.2 billion seedlings grown in the southeastern U.
S. in 2002-2003 fewer than 5% were produced in containers (McNabb and
VandersSchaaf, 2003).  An estimate of less than 10% of the national
forest seedling production is containerized.  Container production is
used for specialty purposes, for example, to reforest mine-spoil sites
which are extremely harsh edaphic environments requiring a soil plug
system to obtain adequate seedling survival (Lowerts, personal
communication, 2003).  

A large investment would be necessary to shift the national production
to containerization, as well as a shift for many nurseries in the
well-established production systems of growing seedlings.  According to
Darrow (personal communication, 2002) the transition from bed to
container production would require additional capital and operating
costs.  Investment would be necessary for the purchases of greenhouses,
container filling and sowing machines, containers, outdoor holding
areas, fertigation systems, and new seedling transport systems both in
the nursery and in the field.  Not all sectors of seedling production
would have this capital available to them.  It is likely that smaller
bareroot operations would close and many state-run nurseries would opt
to close rather than budget state funds for such a significant capital
outlay.  Seedling prices could increase by up to six times current
prices.  A typical one-year old bareroot seedling currently sells for
$0.04 each, while the typical container seedling of the same species
begins at $0.12 each.  In addition to an increase in seedling costs,
there are significant cost increases associated with transportation and
planting container stock.  Fewer container plants can be transported per
truck and fewer seedlings can be carried by individual tree planters. 
More trucks and more fuel are needed to get seedlings to the planting
site and more labor and time are needed to plant a given area.  One
study found that daily production decreased from 9.7 ha per day with
bareroot seedlings to 7.3 ha per day with containerized seedlings, a
decrease of 25%, without increasing planting crew size (Lowerts,
personal communication, 2003). 

The result of containerization would be a significant increase in
reforestation costs and a decrease in the rate of reforestation. 
According to the U. S. Forest Service, 48% of all reforestation in the
U. S. is done on non-industrial private lands, an additional 42% is done
on industrial lands, and 10% on government lands (Moulton and Hernandez,
2000).  Non-industrial forest owners are sensitive to reforestation
costs, decreasing their investment in direct proportion to increasing
costs (Hardie and Parks, 1991; Royer, 1987).  A reduction in
reforestation efforts could have serious long-term negative impacts on
the sustainability of the forest economy.  Industrial owners will also
be negatively impacted by increased reforestation costs as raw material
costs increase (typically about 40-60% of the cost of final fiber
products), impacting the competitiveness of their industry.  

The infrastructure investment necessary for containerization could force
many nurseries out of business.  Seedling production costs would
increase, resulting in seedling price increases of over 250%.  New
transportation and planting systems would have to be adopted. 
Reforestation costs would go up significantly and probably result in
fewer non-industrial forest owners reforesting after harvest.  The
potential long-term effect of these changes on the forestry economy is
enormous.  Overall, containerization would result in a significant
increase in seedling production, transportation, and planting costs and
would most likely decrease reforestation rates.

Benefits of Fumigants for Forest Seedling Nurseries

Tables 2-4 summarize the benefits of methyl bromide + chloropicrin
compared to four feasible alternative fumigants for forest seedlings:
1,3-D + chloropicrin, metam-sodium + chloropicrin, metam sodium, and
dazomet.  Benefits of fumigants include:  (1) yield (quantity produced)
and revenue losses avoided (2) quality (not estimated), which affect the
price or value of seedlings and forest health, and (3) production costs
savings from the higher-cost of using an alternative, additional pest
control requirements, and shifts in other production or harvesting
practices.  However, the cost of purchasing additional equipment needed
to apply metam sodium was not estimated.  This cost would be a one-time
or transitional cost.

The following measures were used to quantify the impacts in Tables 2-4. 
The yield and cost estimates in Tables 2-4 are base on the Methyl
Bromide CUN (critical use nomination for forest seedlings (EPA, 2006)

(1) Benefits per acre.  It is relatively easy to measure, but may be
difficult to interpret in isolation.

(2) Benefits as a percent of gross revenues.  This measure has the
advantage that gross revenues are usually easy to measure; however,
changes of even a small percentage of gross revenues could have
important impacts on the profitability of the activity.

(3) Benefits as a percent of net revenues.  We define net revenues as
gross revenues minus operating costs.  This is a very good indicator as
to the direct losses of income that may be suffered by the owners or
operators of an enterprise.  However, operating costs can often be
difficult to measure and verify.

Table 2.  Benefits of Methyl Bromide and Alternatives in the 
Southeast--Conifers

 Southeast	Methyl Bromide	1,3-D + Chloropicrin	Metam Sodium +
Chloropicrin	Metam Sodium	Dazomet 

Yield Lossa (%) 	0%	3%	3%	5%	5%

   Yield (seedling) per Acre 	300,000 	     291,000 	     291,000 	    
285,000 	     285,000 

* Price per Seedling	$0.042 	$0.042 	$0.042 	$0.042 	$0.042 

= Gross Revenue per Acre 	$12,584 	$12,206 	$12,206 	$11,955 	$11,955 

-  Operating Costs per Acre 	$6,370 	$7,423 	$7,873 	$7,512 	$7,399 

= Net Revenue per Acre	$6,214 	$4,783 	$4,333 	$4,443 	$4,556 

Impact Measures:

1. Per Acre	$0 	$1,431 	$1,881 	$1,771 	$1,659 

2. Percentage of Gross Revenue 	0%	11%	15%	14%	13%

3. Percentage of Net Revenue 	0%	23%	30%	29%	27%

a Yield loss estimates from the Critical Use Nomination for Methyl
Bromide, Table C.1. “Alternatives Yield Loss Summary” (CUN Forest
Tree Seedling Nurseries, 2005 for the 2008 Use Season).  The yield loss
estimates do not address the greater effect of seedling quality for
forest plantings.  Forests planted with undersized seedlings will have
reduced survival and slowed growth if initial seedling health is
compromised.  

Table 3.  Benefits  of Methyl Bromide and Alternatives in the 
Northeast—Conifers and Deciduous

 Northeast	Methyl Bromide	1,3-D + Chloropicrin	Metam Sodium +
Chloropicrin	Metam Sodium	Dazomet 

Yield Lossa (%) 	0%	3%	3%	5%	5%

   Gross Revenue per Acre *	$19,732 	$19,140 	$19,140 	$18,745 	$18,745 

-  Operating Costs per Acre 	$13,241 	$15,376 	$16,051 	$15,241 	$15,681


= Net Revenue per Acre	$6,492 	$3,765 	$3,090 	$3,505 	$3,065 

Impact Measures:

1. Per Acre	$0 	$2,727 	$3,402 	$2,987 	$3,427 

2. Percentage of Gross Revenue 	0%	14%	17%	15%	17%

3. Percentage of Net Revenue 	0%	42%	52%	46%	53%

* From a variety of tree seedlings with different yields and prices per
acre.

a Yield loss estimates from the Critical Use Nomination for Methyl
Bromide, Table C.1. “Alternatives Yield Loss Summary” (CUN Forest
Tree Seedling Nurseries, 2005 for the 2008 Use Season).  The yield loss
estimates do not address the greater effect of seedling quality for
forest plantings.  Forests planted with undersized seedlings will have
reduced survival and slowed growth if initial seedling health is
compromised.  

Table 4.  Benefits of Methyl Bromide and Alternatives in the 
Northwest--Conifers

 Northwest	Methyl Bromide	1,3-D + Chloropicrin	Metam Sodium +
Chloropicrin	Metam Sodium	Dazomet 

Yield Lossa (%) 	0%	3%	3%	5%	5%

   Yield (seedling) per Acre 	24,528 	       23,792 	       23,792 
23,302	23,302

* Price per Seedling	$0.31 	$0.31 	$0.31 	$0.31 	$0.31 

= Gross Revenue per Acre 	$7,591 	$7,364 	$7,364 	$7,212 	$7,212 

-  Operating Costs per Acre 	$4,123 	$4,754 	$4,462 	$4,256 	$4,754 

= Net Revenue per Acre	$3,469 	$2,609 	$2,901 	$2,956 	$2,457 

Impact Measures:

1. Per Acre	$0 	$859 	$567 	$513 	$1,011 

2. Percentage of Gross Revenue 	0%	11%	7%	7%	13%

3. Percentage of Net Revenue 	0%	25%	16%	15%	29%

a Yield loss estimates from the Critical Use Nomination for Methyl
Bromide, Table C.1. “Alternatives Yield Loss Summary” (CUN Forest
Tree Seedling Nurseries, 2005 for the 2008 Use Season).  The yield loss
estimates do not address the greater effect of seedling quality for
forest plantings.  Forests planted with undersized seedlings will have
reduced survival and slowed growth if initial seedling health is
compromised.  

Quantifiable benefits originate from yield losses and cost increases
avoided.  Dazomet and metam sodium have slightly higher yield losses
than 1,3-D + chloropicrin, and metam-sodium + chloropicrin.  Additional
costs for all the alternatives include extra hand weeding and other
pesticide costs.  Indirect yield losses due to lengthening of the
production cycle, resulting in less land in production and more in
fallow or longer time for seedlings to reach appropriate size, were not
quantified.  Additional losses may also arise due to a shift from high
quality Grade #1 seedlings to lower quality Grade #2, which causes a
loss of about 30% of value, and more seedlings that must be culled. 
Unfortunately, data were lacking to measure this shift.  Thus, total
losses are underestimated.

The measure of net revenue impact may not be completely accurate partly
because many nurseries are publicly owned and seedling prices or
production costs are subsidized.  Although attempts were made to
appropriately value the seedlings at a true market price, benefits as a
percentage of gross revenues and of net revenue should be viewed with
caution.  Direct yield effects are similar across the regions, mainly
because the same studies were used to predict impacts.  The range of
yields in the studies is rather large because both dazomet and
metam-sodium provide inconsistent pest control.  Indirect losses arising
from shifts in the production cycle were not quantified.  In the
Northern region this impact is expected to be more pronounced due to
cooler temperatures and longer time required for production of a
seedling crop.  Changes in production costs arise due to differences
between the costs of methyl bromide and the alternatives, shifts in the
production cycle (increasing the frequency of fumigation or lengthening
the fallow period) and additional expenses such as supplementary
irrigation.  These costs vary across regions, because of differences in
pests, production systems, and regional differences in costs of water
and labor.  

Summary of Benefits

Table 5 summarizes the benefits of MB and chloropicrin compared to metam
sodium.  These estimates are conservatively low.  Since metam sodium
provides inconsistent control, these benefits would likely be higher
where control is poor and where pest pressure is high.

Table 5.  Benefits of MB + chloropicrin over metam sodium*

Region	SE	NE	NW

yield gain	5%	5%	5%

per acre	$1,771 	$2,987 	$513 

% of gross revenue	14%	15%	7%

% of net revenue	29%	46%	15%

* the gain of using MB + chloropicrin over metam sodium alone

Yield.  The use of methyl bromide and chloropicrin avoid a yield loss of
at least 5% over metam sodium.  Where pathogen pressure is great the
yield losses would be larger.  If 1,3-D were the only fumigant
available, then the yield losses could be greater.  However, we have no
data to quantify these yield losses.  Yield data comparing all the
fumigants would be helpful, particularly yield with using metam sodium
or 1,3-D without chloropicrin.

Pest Control Costs.  Fumigants, particularly MB and chloropicrin, reduce
the need for hand weeding and other pesticides, thus saving operating
costs. 

Quality.   MB and other fumigants result in a larger percent of higher
quality seedlings.  The lower quality seedlings are discarded or have a
lower value or price.  These benefits could not be quantified, however.

Forest Health.  Seedlings free of pathogens and other pests help
establish forests with less pest pressure, thus resulting in faster
growth and less use of pesticides.  These benefits were not quantified.

Limitations of Analysis

Yield data.  BEAD was only able to quantify yield losses of up to 5%. 
However, metam sodium and dazomet can have erratic results often with
yield losses greater than 5%; however, we have no basis to estimate this
loss.  Also, we have no yield data for 1,3-D and metam sodium used alone
without other fumigants.  Such data would be useful to BEAD.

Delays in Production.  Impacts associated with delays in planting as a
result of using alternatives to MB were not estimated.

Prices and Costs.   The prices of seedlings, fumigation costs, and other
operating costs were based on the 2004 economic analysis that was used
for the current MB CUN (Critical Use Nomination).  Prices and costs may
have changed since then; however, we believe relative cost impacts have
not changed much.  The costs of additional equipment required to treat
with metam sodium (for those nurseries not currently using metam sodium)
was not estimated.  

Quality Impacts.   We have no basis to estimate the impacts on the
quality of seedlings and the impacts of spreading pathogens and other
pests into the forests as a result of contaminated seedlings.

Partial Budgeting.  The impact estimates were made by comparing budgets
with MB and chloropicrin to budgets with alternative fumigants.  Such
analyses do not consider transitional costs from one production method
to another, nor adoption to new production methods over time, which may
mitigate the impacts.

Conclusions

Soil fumigation with methyl bromide and/or chloropicrin for management
of soil-borne pests provides substantial benefits to tree seedling
nurseries and to the public.  While relatively few acres are treated
each year, good nursery practices contribute to health of tree seedlings
and to the long-term health of forests.  The value of methyl bromide in
part depends on the availability of chloropicrin, since methyl bromide
is currently used in combination with chloropicrin.  The estimate of the
benefits of chloropicrin is in comparison to production with
metam-sodium, which is less effective on most soils because it does not
penetrate as well.  In addition, use of metam-sodium is more costly
because it cannot be applied simultaneously with 1,3-D for nematode
control.  Chloropicrin is also necessary as a component of a methyl
bromide alternative, 1,3-D + chloropicrin.  This combination has been
tested and in some nursery locations has been found to be an effective
alternative to methyl bromide.  However, without chloropicrin, 1,3-D is
generally not effective for managing soil-borne pathogens or weeds.

Soil fumigation with methyl bromide + chloropicrin, in general, makes
nursery tree production viable on nearly half the nursery acreage
currently cultivated.  If soil pests cannot be adequately controlled,
the costs of establishing a nursery would likely outweigh the value of
future revenue.  Thus, the direct benefits of soil fumigation to manage
nursery pests are increased yield  and reduced production costs.  These
benefits are estimated to be at least 15-46% of net revenue.  In
addition, the non-quantified benefits include increased tree quality and
forest health in the U.S.

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 Tables 2-4 show that the net revenues are greater with metam sodium
than with metam sodium + chloropicrin.  However, chloropicrin is
considered very important and in many cases worth the extra cost, but is
not cost effective if the yield gain is only 2% over metam sodium alone.
 Therefore, we believe that the yield benefit of chloropicrin is greater
than 2% in many cases.  In addition, there are likely to be quality
benefits.

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