Methyl bromide alternatives

14 Pages·1996·3.1 MB·English

Historic, Archive Document
Do not assume content reflects current
scientific knowledge, policies, or practices.

aSB952
-B75M47 yl bromide alternatives
Vol. 2, No. 3 July 1996
tt. Ao
OS) AY Cod velop, uncertainty about the potential
impact of certain pests on seedling
Bromide: The USDA
production, and an inability to prevent
and control pests through alternative
Forest Service
practices essentially mean that fumi-
Perspective
gation is currently the nursery
manager’s best “insurance policy”
Research conducted by USDA’s For- against potential problems.
est Service, combined with the efforts
“We're aggressively seeking to de-
of cooperators and the insight of nurs-
velop better integrated pest manage-
ery managers, could help develop inte-
grated pest management programs ment programs that will provide nurs-
ery managers with the necessary infor-
that will be needed when methy! bro-
mation to manage complex pest prob-
mide is no longer available.
lems through alternative chemical,
cultural, physical, and biological con-
The impending loss of this chemical
and the major concerns expressed by trol practices,” Sesco reports. “Our
various commodity groups, including goal is to provide nursery managers
ornamental and forest nurseries, have with the best information possible to
underscored the heavy reliance on me- manage potential pests.”
thyl bromide to provide broad-spec-
To accomplish this, the Forest Service
trum control for pest problems.
is supporting research efforts at its
“The potential loss of methyl bromide laboratories in Athens, GA, and St.
has emphasized the need for a better Paul, MN. In addition to the Forest
understanding of the pest problems Service’s State and Private Forestry
that affect forest tree nursery produc- and National Forest System, coopera-
tion in the United States and for the tors include USDA’s Agricultural Re-
Inside This Issue development of alternative strategies search Service, State natural resources
to prevent and control these prob- agencies, universities, and commercial
and industrial nurseries. Research col-
lems,” says Jerry Sesco, the Forest
Service (FS) deputy chief for research. laborators are investigating alternative
Loss of Methyl Bromide:
pest management practices and col-
Forest Service Perspective
Many nursery managers presently rely lecting information that will be used in
A Proposed New Quarantine on routine fumigation with methyl developing integrated pest manage-
Treatment for Fruit Flies bromide because of its broad-spectrum ment (IPM) programs. Research ef-
ability to control diseases, nematodes, forts include collecting information on
Telone C-17: Possible Replace-
insects, and weeds that can affect factors that influence pest outbreaks
ment for Methyl Bromide
seedling production and quality, ac- and developing alternative pest man-
on Bell Peppers
cording to Sesco. A basic lack of un- agement strategies to prevent and
Potential Alternatives to derstanding of how pest problems de- control losses.
Methyl Bromide
for Floricultural Crops
This newsletter provides information on research for methyl bromide alternatives from
Broccoli: A Potential Alternative USDA, universities, and industry.
to Chemical Soil Fumigants
Address technical questions to Kenneth W. Vick, USDA, ARS, National Program Staff,
Alternatives Being Explored Bldg. 005, Room 237, BARC-West, 10300 Baltimore Ave. Beltsville, MD 20705.
Phone [phone], Fax [phone].
in Germany
Technical Reports Address suggestions and requests to be added to the mailing list to Doris Stanley,
USDA, ABS, Information Staff, 6303 Ivy Lane, Room 444, Greenbelt, MD 20770.
Upcoming Meetings Phone [phone], Fax [phone].
U.S. Department of Agriculture
Vol. 2, No. 3 Methyl bromide alternatives, July 1996
“Our strategy has been to focus on de- and Dwinell from the Athens lab to re- quality is reduced and mortality in-
veloping both short- and long-term fine techniques for use of dazomet in creased in other nonfumigated fields.”
IPM systems,” says Stephen W. southern nurseries beginning this fall.
Fraedrich. An FS plant pathologist at The impact of fungi and nematodes on
the Southern Forest Experiment Sta- Researchers at the St. Paul station seedling production is of particular in-
tion in Athens, GA, he and colleague have extensively screened potential terest, he says.
L. David Dwinell are working with biological control agents to suppress
plant pathologists Jennifer Juzwik and the pathogenic soilborne fungi. “In the North Central States, soil-
water management is critical in con-
Cynthia M. Ocamb, who are located at
the FS North Central Forest Experi- “Preliminary studies showed that ap- trolling root diseases,” reports Juzwik.
plying selected bacteria, along with “Maintaining optimal soil moisture is
ment Station in St. Paul, MN.
ectomycorrhizal fungi, protects con- a key factor in minimizing Fusarium
“In the short term, it is imperative that tainerized seedlings against various losses in both fumigated and
IPM systems are developed which will Fusarium fungi,” Juzwik says. nonfumigated nursery beds.”
minimize or prevent the disruption to ‘“We’re also conducting bareroot nurs-
U.S. forest tree nursery operations be- ery field trials with these same antago- “We have also examined the effect of
cause of the loss of methyl bromide,” nistic, beneficial microorganisms.” bare-fallowing, which can control dis-
ease losses in the Pacific Northwest
Fraedrich says. “Therefore, we’re
placing greater emphasis on the use Scientists at the Athens lab are study- nurseries,” she continues. “But we
and application of other soil fumi- ing seedborne fungi and their possible have found that this practice is not ef-
gants as well as other pesticides for role in disease development in nurser- fective for the control of root diseases
these short-term systems. However, ies. Seed orchard and cone harvesting in the North Central States.”
conditions are being studied because
because of increasing public attention
they may influence the establishment Future research efforts by the Forest
to environmental and health issues,
there are likely to be increasing chal- of pathogenic fungi with seeds. Service will include assessments of
They’re also evaluating the efficacy of
lenges to using other chemicals in the
a nonpathogenic bacterium, e soil solarization
future. For the longer term, we’re
Burkholderia cepacia, that is report-
working to develop cultural, physical,
¢ the impact of cover crops and
edly antagonistic to some plant patho-
and biological pest management strat-
organic amendments on soil-
genic fungi.
egies as well as a better understanding
borne pests such as nematodes
of precisely when specific chemicals
At both locations, FS scientists are ex- and pathogenic fungi
are needed.”
amining ways to disinfest the surface
¢ efficacy studies of other pos-
of seeds with chemicals such as hy-
In St. Paul, Juzwik and colleagues
sible chemicals
drogen peroxide as well as investigat-
have refined application methodology
ing potential biocontrol agents to sup-
of the chemical dazomet, enhancing
e factors that influence the devel-
press seedborne pathogens.
its efficacy for field soil sterilization
opment of pest problems
and control of root diseases in conifer
Efforts are also under way at both lo-
seedlings.
* various combinations of chemi-
cations to determine the underlying
cal, cultural, physical, and bio-
causes of disease development.
“Root diseases caused by fungi such
logical pest control strategies.
“Studies done in Georgia show that
as Cylindrocladium spp., Fusarium
seedling quality was increased in some
spp. and Pythium spp. are a major
Even if a single chemical alternative is
nursery beds by fumigation,” explains
problem facing forest nurseries,” ex-
found to replace methy] bromide, a
plains Juzwik. “In trials in the North Fraedrich. “But in other beds, we’ ve
more integrated approach for manag-
Central States we’ ve found dazomet as observed no differences in seedling
ing pests over the long term is needed
quality in fumigated and non-fumi-
effective as methyl bromide in con- because of increasing environmental
gated treatments. We want to know
trolling root diseases, with no harmful and human health concerns about
why certain fields remain productive
effects on seedling quality.” She and
chemical use. Resourceful forest
colleagues will work with Fraedrich without fumigation, while seedling
managers working with research orga-
2
U.S. Department of Agriculture
Vol. 2, No. 3
Methyl bromide alternatives, July 1996
nizations, including FS researcher sci- proach to be applicable as a treatment
Telone C-17: Possible
entists, could help the industry live against Mexican fruit fly in citrus dur-
without methy] bromide. ing processing and containerized ship- Replacement for
ping,” Mangan says. The in-transit pe-
Methyl Bromide on
riod for produce being shipped from
production areas is typically 1 to 3 Bell Peppers
A Proposed New weeks. Mangan’s approach would in-
clude placing recording devices in
Quarantine Treatment Experimental research by Southwest
multi-ton shipping containers to track
Florida Farms, a division of Gargiulo,
for Fruit Flies the actual gas mixture and temperature
Inc., Immokalee, FL, shows that
over time. That way, inspectors at the
Telone C-17 worked as effectively as
receiving port can determine the
ARS entomologist Robert Mangan methyl bromide in fumigating soil to
treatment’s integrity.
hopes that a combination of controlled rid it of pests before planting bell pep-
temperature and an altered mix of pers.
The specific mixtures of oxygen, ni-
oxygen, nitrogen, and carbon dioxide
trogen, and carbon dioxide gases are
can keep shipped citrus free of live “There were no obvious differences in
proprietary information of the
Mexican fruit flies, a quarantine pest control of nematodes or soilborne dis-
project’s industry partner,
in California and Texas. Parts of eases in plots fumigated with methyl]
TransFRESH Corp., Salinas, CA.
California’s San Diego County are bromide and those treated with the
ARS has a Cooperative Research and
currently under quarantine for this chemical Telone C-17,” says Tom
Development Agreement with
fruit fly. Mangan is proposing the Mueller. Director of research and de-
TransFRESH to test the new method
new treatment as an alternative to me- velopment for Gargiulo, Mueller says
for 3 years. Under this agreement, re-
that both treatments controlled the
thyl bromide, the chemical fumigant
searchers will look for the perfect in-
now being used that will be discontin- weed nutsedge fairly equally. He
transit treatment that will protect cit-
ued by 2001. combined Devrinol herbicide with
rus, mango, avocado, and other fresh
Telone as an in-bed treatment.
fruit from pests such as Mediterra-
He is testing the proposed method on
grapefruit at the ARS Crop Quality nean, Mexican, Caribbean, and other “We planted bell peppers in
fruit flies.
Immokalee back in January of this
and Fruit Insects Research Unit in
year, which is a late planting for this
Weslaco, TX. His goal is in-transit
“Keeping shipped U.S. produce free
treatments against the threat the Mexi- area of Florida,” he says. “The late
of pests is essential to maintain and
winter was also particularly cold,
can fruit fly poses for any citrus crop
expand markets here and elsewhere,
grown in California or Texas. “We which delayed crop growth. So, we
such as in Pacific Rim countries,”
are testing lots of combinations of the only harvested the crop twice. First
Mangan says.
harvest yields were considerably
gases,’ Mangan says. “Results are not
conclusive, but some combinations ap- Typically, USDA’s Animal and Plant higher from the Telone treatment, but
pear very effective at killing Mexican the second-pick yields were higher
Health Inspection Service requires that
from the methyl bromide treatment.
fruit flies.”
a method must kill 99.9968 percent of
However, overall yields were slightly
pests before it can be approved as an
Krista Shellie, a plant physiologist at higher from the Telone treatment.”
official quarantine treatment.
Weslaco, is testing fruit quality for the
Mueller’s research was part of a large-
quarantine treatments program.
scale study initiated and conducted by
Grapefruit hold up well for a number
DowElanco in collaboration with the
of the proposed treatments.
U.S. Environmental Protection
Even if this approach succeeds, it Agency and the State of Florida’s De-
would be only one of many kinds of partment of Agriculture and Consumer
methyl bromide alternatives that are Services and its Department of Envi-
needed. “We would expect this ap- ronmental Protection.
U.S. Department of Agriculture
Vol. 2, No. 3 Methy! bromide alternatives, July 1996
In December 1995, Mueller and col- decades. Development of alternatives We experimented with buried
leagues treated one-half of a 16-acre for the diverse crops and horticultural manifolds, but found that this method
field with Telone C-17, using conven- practices inherent in the nursery and doesn’t uniformly heat the soil,”
tional farm equipment. They injected greenhouse industries is a significant MacDonald states.
the chemical into a preformed, raised challenge.
bed and immediately covered it with Another method he is using is called
polyethylene plastic mulch. About James MacDonald, a plant pathologist ohmic heating. This involves passing
22.5 gallons of Telone per acre were with the University of California electrical currents between an anode
applied. Prior to bed formation, they (UC), Davis, and several colleagues and a cathode in the soil, a process
applied Devrinol herbicide at a rate of have been experimenting with which generates heat by the soil’s
3 pounds per acre to control nutsedge. potential alternatives to methyl resistance to the flow of the current.
bromide for Fusarium wilt. This wilt, MacDonald and colleagues use rows
“Using the same equipment, we ap- caused by the fungus Fusarium of steel rods, driven into the ground on
plied methyl bromide and chloropicrin oxysporum f.sp. dianthl, is the most either side of an empty bed, as anode
(98 %/2%) to the remainder of the devastating disease of carnations. and cathode arrays.
field on the same day,” says Mueller. MacDonald’s collaborators are
Manuel Lagunas-Solar, UC-Davis; According to MacDonald, they have
A month later, bell pepper transplants Steve Tjosvold, a farm adviser from been able to heat the soil and kill
were put in the treated field, and irri- Salinas, CA; Howard Ohr, UC- Fusarium at a depth of 3 feet by
gated and fertilized through drip irri- Riverside; and Ian Green, Salinas driving these rods that depth into the
gation. Field soil type was a Myakka Flower Grower’s Co-Op, Salinas. soil.
fine sand, common in southern
Florida, a growing area characterized “We’re investigating both chemical In addition to soil heating, they’v e
by sandy soils, high rainfall, and a and nonchemical alternatives,” tested surface applications of methyl
naturally high water table that is con- MacDonald says. One approach of bromide (to represent current
sidered environmentally sensitive. particular interest to MacDonald is practice), methyl iodide, and Basamid.
soil heating. Known to be an “In our experiments, methyl iodide
“Crop growth on the complete experi- effective, nonchemical means of provided better control than methyl
mental site was normal and vigorous,” killing soilborne pests and pathogens, bromide,” MacDonald says. However,
Mueller reports. “We plan to continue heat “is an approach particularly well efficacy of all chemicals appeared
this research in the 1996-97 growing suited to ornamental production limited to the upper foot of soil.
season to get data on side-by-side because of the high value of the “Ohmic heating was the only
comparisons of methyl bromide and growing media and the crops,” he treatment that killed Fusarium spores
Telone C-17.” Says. to depths greater than | foot.”
MacDonald and colleagues have been Some carnation growers are
experimenting with steam and converting their operations to raised
MIKI IOAN Kaw IFTAAYos
electronic processes for soil heating. beds to escape the fungal spores
to Methyl Bromide for “The nursery industry has a long surviving in the soil. While Fusarium
history of using steam,” he says. “It’s wilt can occur in raised beds, the
Floricultural Crops
a technology they’re comfortable relatively shallow, small soil volumes
with.” are more easily treated by steam. But,
Producers of nursery and ornamental MacDonald says that disease
crops have relied on methyl bromide However, steam doesn’t heat ground outbreaks in steamed beds are not
for many years to control weeds and beds deeply enough to eliminate uncommon. The pathogen probably
soilborne pathogens in ground beds Fusarium from carnation’s root zone. gets reintroduced through workers or
and mixes of potting media. For some airborne spores. “I’ve recovered the
diseases, such as Fusarium wilt of “Some growers buried steam pathogen from particles of dust carried
carnation, methyl bromide has been manifolds a foot deep in the soil but on air currents within the greenhouse,”
the primary means of control for still didn’t achieve effective control. he says.
4
U.S. Department of Agriculture
Vol. 2, No. 3 Methyl bromide alternatives, July 1996
One concern with steaming potting
He says there is also a compound in
Broccoli: A Potential
media or raised beds is that it’s
broccoli (absent in cauliflower) called
difficult to control temperatures with Alternative to Chemi-
glucoraphanin that possesses antimi-
steam, so soils may be overheated,
cal Soil Fumigants crobial properties. As broccoli decom-
eliminating beneficial organisms as
poses, it produces volatile chemicals
well as pathogens.
that may have an effect on soilborne
Cauliflower brings growers in coastal pathogens.
“The absence of competing organisms California about $168 million each
can allow pathogens to readily year. On 52,000 acres, these growers “We tested the pathogenicity of V.
recolonize soils,” notes MacDonald. raise nearly 80 percent of the cauli- dahliae isolates from several crops,”
For this reason, he is collaborating flower produced in the United States Subbarao says. ‘‘Our conclusions
with James Locke, ARS, to evaluate for both fresh and processing markets. show that rotations of cauliflower with
potential biological controls. Locke is
any crop other than broccoli, Brussels
with the ARS Floral & Nursery Plants “But a sudden and widespread in- sprouts, and perhaps lettuce, would
Research Unit in Beltsville, MD. crease in Verticillium wilt has taken likely increase the incidence of wilt.”
MacDonald plans to incorporate several fields out of production in the
Locke’s “biologicals” into raised beds Salinas Valley,” says Krishna V. Salinas Valley growers routinely rotate
after steaming to try to prevent the Subbarao, a plant pathologist with the cauliflower with lettuce, maintaining
fungus from re-establishing. University of California, Davis. levels of microsclerotia in the soil.
“Growers suffer extensive losses on Therefore, rotations with lettuce will
USDA, the California Cut Flower crops harvested between April and not control the fungus on cauliflower
Commission, and the California October.” or other susceptible crops in the short
Association of Nurserymen are term, according to Subbarao. He and
funding this research. MacDonald and Since there is no effective control, colleagues tried broccoli to reduce the
colleagues are just entering their Subbarao says that the wilt, caused by microsclerotia in soil and wilt on cau-
second year of field trails and are still the fungus Verticillium dahliae, pre- liflower. They chose cauliflower as a
analyzing data from the first year of sents a significant threat to other cool- model system because of its impor-
research. Preliminary results show the season vegetable crops as well. Verti- tance to California agriculture and be-
following: cillium wilt attacks more than 300 cause broccoli is grown extensively in
kinds of plants. The fungal the Salinas Valley. Most of the funds
¢ Ohmic heating was the only microsclerotia live in soil or on decay- for this research project came from
treatment that killed fungal spores ing organic matter in the soil and can several California cauliflower growers,
to a significant depth in the soil. survive for up to 15 years. with some financial support from
ARS.
¢ Surface-applied fumigants killed Subbarao and colleagues have found a
the fungus only in the uppermost way to control the devastating wilt on Subbarao conducted his research in
parts of the soil. cauliflower without using chemicals:
experimental and grower fields. His
working chopped-up broccoli into the 2-year study demonstrated that broc-
¢ Methyl iodide appears more soil before planting cauliflower.
coli residue reduces the number of
effective in surface applications
microsclerotia in the soil and de-
than methyl bromide does. “Although cauliflower and broccoli
creases the incidence of Verticillium
are related, broccoli resists the wilt
wilt, making broccoli an ideal candi-
In addition to controlling pathogens in even when it is planted in soil heavily
date for rotation with cauliflower.
ground- and raised-bed cropping infested with microsclerotia. Even
systems, MacDonald and Lagunas- broccoli roots are pathogen free, and
“We applied freshly cut broccoli
Solar are exploring the use of since broccoli growers haven’t com- shoots to experimental plots and im-
microwaves to pasteurize potting plained about the disease, it evidently
mediately worked them into the soil,”
media for greenhouse and nursery use. isn’t a problem,” Subbarao says.
Subbarao says. “Our results show that
less wilt developed on cauliflower in
U.S. Department of Agriculture
Vol. 2, No. 3 Methyl bromide alternatives, July 1996
these plots than in plots fumigated flower and possibly other crops as of the Institute for Stored Product Pro-
with synthetic chemicals.” well. “This would not only reduce tection, which is part of the Federal
the wilt, but would also help the envi- Biological Research Center for Agri-
Tarping had no effect on controlling ronment by cutting the use of syn- culture and Forestry in Berlin and
the fungus. One of the important find- thetic pesticides,” he says. “We think Brunswick.
ings was that the numbers of that broccoli could be an economically
microsclerotia declined throughout the viable substitute for chemical fumi- “However, we are urgently searching
season and stayed low the following gants. The number of years a crop for ways to modify and optimize our
season. However, in conventionally needs to be rotated with broccoli de- existing use of methyl bromide,” he
fumigated plots, the numbers declined pends on the magnitude of soil infesta- says. “There is a chance that we can
initially but increased toward the end tion by the pathogen.” further reduce our dosage and still kill
of the season. This suggests that pests in stored goods.”
while fumigation gives short-term Broccoli’s applicability to other crop-
control, the effects of broccoli residue ping systems needs to be thoroughly According to Reichmuth, the seals in
are longer term. researched, Subbarao says. Although structures being fumigated are rou-
it would probably work as a tinely tested to ensure quality prior to
Subbarao isn’t sure just how broccoli biocultural control on strawberries and methyl bromide treatment, often cut-
protects cauliflower from wilt. It other crops, its success should be dem- ting down on the amount of the chemi-
could be a chemical or a biological onstrated commercially for these crops cal needed. Even in a fairly gas-tight
mechanism, or both. Applying fresh- before it is recommended. building, Reichmuth says, about 50
cut broccoli could increase the num- percent of the methyl bromide used in
bers and types of beneficial soil mi- “We propose that broccoli could be a a treatment can be lost in 2 days.
croorganisms such as actinomycetes, possible alternative for methyl] bro-
bacteria, and fungi, which would se- mide, the fumigant now used by veg- “In a large-scale experiment, we’re us-
lectively inhibit the activity of the etable and strawberry growers in Cali- ing charcoal to adsorb methyl bromide
fungus. fornia,” he says. Methyl bromide is instead of venting the gas into the air
scheduled to be banned by the U.S. at the end of fumigation,” he says.
“The results so far indicate that it may Environmental Protection Agency by “But, we need to consider the large
be a combination of both chemical and 2001. amounts of charcoal that would be
biological. Any effect of the chemi- needed to significantly decrease gas
cals is transient since they are volatile emissions. To be effective, we would
and stay in the soil for only a short need to cut emissions by 50 percent.”
Alternatves Being
time,” Subbarao notes.
Explored in Germany In addition to chemicals, since the
“Tn soil amended with broccoli, the early 1920’s the Germans have been
number of actinomycetes and bacteria studying the use of a parasitic wasp,
In Germany, methyl bromide is used
increased 1,000 fold, while the num- Trichgramma evanescens, to control
primarily to fumigate structures like
bers of fungi increased only slightly moths that cause problems in flour
flour mills and food factories to con-
compared with soil not treated with mills. Two of Reichmuth’s colleagues
trol pests in stored products. Some of
broccoli residue.” These microorgan- at the Institute, Sabine Prozell and
the 90 tons used annually is to control
isms may have a direct deleterious ef- Matthias Schoeller, are using the wasp
beetles that destroy altars and other
fect on the microsclerotia; indirectly, against the warehouse moth (Ephestia
precious wooden artifacts in churches
the secondary metabolites produced elutella), and the Indian meal moth
and museums.
by these microorganisms may also (Plodia interpunctella). In Germany,
have an effect. these insects are severe pests in stored
Christoph Reichmuth says that Ger-
grain and the food processing
many has greatly reduced its use of
Subbarao’s results indicate that after industry.
methyl bromide, but is still investigat-
commercial harvest, growers could
ing chemical, nonchemical, and inte-
plow under broccoli residue to manage “Preliminary results are promising that
grated pest management strategies as
Verticillium wilt in subsequent cauli- these wasps will find their place in
possible replacements. He is director
6
U.S. Department of Agriculture
Vol. 2, No. 3 Methyl! bromide alternatives, July 1996
controlling pests of stored products,” a problem in Germany as there is in Treatments developed as alternatives
Reichmuth reports. “We hope they the United States, of registering these to methyl bromide (MB) fumigation of
may replace some chemical control extracts since they are mixtures of sev- postharvest commodities for
agents.” eral chemicals. quarantined insects must address
concerns of fresh fruit injury as well
He says they have shown that con- “Our postharvest pest control market as efficacy on target insect(s).
trolled temperatures, heat and cold, are is rather limited and does not guaran- Although consumers might tolerate
a possible replacement for methyl bro- tee a quick amortization of the regis- certain minor cosmetic injuries to fruit
mide in smaller flour mills. However, tration cost,” Reichmuth says. peel if no other treatments are
he says they have encountered prob- “Therefore, the registration process is available, any commodity treatments
lems with obtaining even distribution slow.” causing major blemishes and decay
of heated and slightly humidified air. will not be tolerated or used in
Heat treatments must be repeated One of the research areas of the future commercial situations even if such
more often than methyl bromide treat- for German scientists is in early detec- treatments are approved by regulatory
ments throughout the year. Other than tion and monitoring of insects. Since agencies.
with methyl bromide fumigation, com- nearly all pheromones of important
plete control of all stages of insects in pests of stored products are detectable Currently, we are evaluating an
various crevices in structures and in- and can be synthesized, these are im- APHIS-approved fruit fly quarantine
side machinery is hard to achieve. portant aspects of integrated pest man- treatment using a combination of a
They’ve observed insects trying to es- agement. German scientists plan to reduced MB fumigation dose followed
cape heated machinery during a heat combine pheromone traps with insec- by a short cold treatment. These
treatment. ticides or biocides like viruses, Bacil- treatments use 32 g MB/m, less MB
lus thuringiensis,or entomophagous than is required when MB is used
Regarding cold, both moderate and fungi. alone (thereby reducing emissions of
deep cold treatments are used in Ger- MB from postharvest commodity
many, in the form of liquid nitrogen or “The way of the future may mean that fumigations), combined with short
air, carbon dioxide, or electrical cool- we use biotechnology to produce new cold treatments, shorter and warmer
ing. types of insecticides or insect-resistant than when cold treatments are used
products,” says Reichmuth. “Our alone. These short cold treatments
Other chemicals that the Germans are search for a cheap, versatile replace- used in conjunction with MB are less
trying as substitutes for methyl bro- ment for methyl bromide is far from stringent than the longer or stand-
mide include carbonyl sulfide and sul- over.” alone cold treatments and reduce the
furyl fluoride, as well as combinations expensive time-consuming cold
of phosphine and carbon dioxide and treatments that delay marketing of
carbon dioxide under high pressure. citrus and increase fruit senescence
Technical Reports and decays.
“We’ve found that elevated tempera-
tures along with phosphine or mix- In several tests completed with lemons
tures of carbon dioxide or nitrogen Reducing Citrus Fruit Injury From and navel oranges, we have found that
with low amounts of oxygen fulfill the aeration after fumigation and before
Combination Treatment of Reduced
requirement of quick disinfestation,” Methyl Bromide Dose Plus Short initiation of the cold treatment is of
Reichmuth says. Like methyl! bro- prime importance. However, an
Cold Treatment
mide these methods leave little or no important, and limiting, requirement
residue, but they are more expensive. Laurie G. Houck, Research Plant of the MB + cold treatment
The original research, he says, was Pathologist and Joel F. Jenner, combination is that cold treatment
done by ARS scientists. Biological Science Technician; must be initiated within 24 hours after
Postharvest Quality and Genetics MB fumigation.
Although the Germans are investigat-
Research Unit, USDA, ARS, Fresno,
ing natural insecticides as potential al-
CA 93727. Lemons aerated for the full 24 hours
ternatives to methyl bromide, there is did not develop objectionable rind
U.S. Department of Agriculture
Vol. 2, No. 3 Methyl bromide alternatives, July 1996
injury discoloration or pitting Southwest Florida Research & Nutsedge, both yellow and purple, was
symptoms characteristic of MB injury Education Center, Immokalee, FL one of the most difficult pests to
and of cold injury (chilling injury; CI). 33934. control for any alternative chemical.
However, sometimes a noticeable mild Purple was more difficult to control
Fresh market tomatoes, produced on and more prevalent in tomato fields in
peel injury did develop even on
lemons aerated the maximum allowed about 50,000 acres and worth up to the southern portion of the state where
24 hours. This injury would probably $450 million annually, are a major most tomatoes are grown. This weed
not be a major impediment to horticultural industry in Florida. Most is capable of penetrating the
marketing lemons. Injury was more of the winter tomatoes consumed in polyethylene mulch covering plant
severe on navel oranges than on the U.S.come from Florida, where beds; since control is difficult once
lemons and the navel orange injury they are grown on raised, polyethylene nutsedge emerges, it, therefore,
might not be accepted by consumers. mulched beds. Most plants are staked flourishes without competition.
We have only tested late-season to improve air movement, which
reduces relative humidity and We evaluated older, registered
navels, however, and this may not be
true for early-season navels. Injury to incidence of foliar disease, and to keep chemical fumigants as well as some
both lemons and navel oranges the fruit from contacting the soil experimental products and tested
increased markedly as aeration time which limits fruit rot. The mild efficacy in areas infested with various
was decreased. Injury that developed climate and sandy soils which favor important soil-borne pests. These
on fruit after short aeration times was crop production also favor many soil- included root knot nematode,
severe and would not be tolerated. borne pests of tomatoes and other Fusarium wilt, Fusarium crown rot,
crops. Thus, soil fumigation is vitally Southern blight, bacterial wilt, and
A full 24-hour aeration would delay important in producing tomatoes in purple and yellow nutsedge. Each
marketing of fruit, and the warm Florida. product had its limitations, some more
fumigation/aeration temperature limited than others. Telone C-17
required (21°C) could sometimes lead The search for fumigant alternatives to provided good control of nematodes
to an increase in normal rind methyl bromide for Florida’s tomato and some soil-borne diseases; whereas
production began in 1993. What a
senescence or injury and fruit decay in chloropicrin controlled diseases well,
storage/shipping/marketing. handful of Florida scientists started as but not nematodes. Vapam and
fragmented research on various Basamid were quite erratic intheir
Further tests to evaluate the value of aspects of soil fumigation has grown performance. Enzone, an
forced shorter aeration times into a well-coordinated research and experimental nematicide, failed to
following MB fumigation to rapidly extension program with participation control nematodes and damaged
remove MB from the fruit and cartons from the University of Florida, the tomato plants in some experiments.
and lessen fruit rind injury will be Florida Tomato Committee, the Fosthiazate, another experimental
investigated. Florida Fruit and Vegetable nematicide, controlled nematodes
Association, and the USDA-ARS. erratically and did not control other
Some funding also has been provided pests. None of the products controlled
by the U.S. Environmental Protection nutsedge consistently; in some cases, a
Possible Soil Fumigant Alternatives
Agency. Soil fumigant field trials, few actually increased emergence. It
for Methyl! Bromide in Mulched
standardized early on, were conducted became evident that nutsedge control
Tomato Production
in most of Florida’s tomato producing would have to be addressed separately
areas, as well as on the main campus with herbicide. In evaluating these
J. P. Gilreath and J. P. Jones,
of the University of Florida. We pesticides, we tried to intergrate them
University of Florida, Gulf Coast
evaluated various soil fumigants for into standard tomato production
Research & Education Center,
soil-borne disease, nematode and practices of Florida’s raised bed,
Bradenton, FL 34203; J. W. Noling,
weed control. It was apparent from polyethyelene mulch cultural system.
University of Florida,Citrus Research
early trials that no one fumigant would Since this system was designed to use
& Education Center, Lake Alfred, FL
control all of the soil- borne pests that a liquid fumigant which could be
33850; and R. J. McGovern,
methyl] bromide does or as well as delivered to the soil under pressure
methyl bromide. through chisels, liquid fumigants
8
U.S. Department of Agriculture