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pinholes (at least 49 per square inch). These holes enhance
permeability through the plastic fruit trays, which are frequently used
for transport of fruit.
Kraft Paper and Corrugated Cartons
Kraft paper is permeable to MB and does not need to be removed prior
to fumigation. Corrugated cartons are also permeable to MB and
unless impermeable liners are present, aeration will be satisfactory,
although it will be slower in closed boxes.
Wooden Boxes
Although MB penetrates wooden boxes, aeration of tight boxes may be
slow, particularly if sorptive packing materials are present. To aid in
aeration, have the lids removed and boxes placed on their sides prior
to fumigation. If removing lids is not practical, then increase the
aeration time.
Sorption
Sorption is the process of chemically or physically binding free MB on
or within the fumigated commodity. Sorption makes the fumigant
unavailable to kill the plant pest. There are three types of
sorption—absorption, adsorption, and chemisorption. Sorption rate is
high at first, then gradually reduces to a slow rate. Sorption increases
the time required for aeration.
Important
Inform prospective importers that the wrappings on their shipments may have
to be perforated to PPQ specifications, removed, or opened if PPQ requires
fumigation. If wrappings on shipments are designed to satisfy PPQ
requirements for fumigation readily, importers could save time and money.
Shippers may send samples of prospective wrapping materials (a piece at
least 12in X 12in) to Oxford Plant Protection Laboratory for evaluation.
Chemical Treatments Fumigants • Methyl Bromide
Residual Effect
2-3-6 Treatment Manual 10/2002-04
PPQ
Commodities known or believed to be highly sorptive should not be
fumigated in chambers unless concentration readings can be taken to
ensure the required minimum concentration is met. Additional
readings may be necessary in order to properly monitor gas
concentration sorptive commodities in chambers.
For tarpaulin fumigation, additional T/C unit readings are necessary
to monitor concentration of gas to determine the rate of sorption. The
following is a partial list of commodities known to be highly sorptive:
◆ bales of burlap
◆ myrobalan
◆ carpet backing
◆ pistachio nuts
◆ cinnamon quills
◆ polyamide waste
◆ cocoa mats
◆ polystyrene foam (Styrofoam)
◆ cotton
◆ potato starch
◆ flour and finely milled products
◆ rubber (crepe or crude)
◆ gall nuts
◆ vermiculite
◆ hardboard (Masonite™)
◆ wood products (unfinished)
◆ incense
◆ wool (raw, except pulled)
Call the Oxford Plant Protection Laboratory if you are concerned about
the sorptive properties of other commodities. (Telephone:
919-693-5151)
Residual Effect
MB may adversely affect the shelf life of fresh fruits and vegetables,
the viability of dormant and actively growing plants, and the
germination of seed. Although MB may adversely affect some
commodities, it is a necessary risk in order to control pests. Some
Chemical Treatments Fumigants • Methyl Bromide
Residual Effect
10/2002-04 Treatment Manual 2-3-7
PPQ
dosage rates are near the maximum tolerance of the commodity, so
care must be exercised in choosing the proper treatment schedule and
applying the treatment.
MB may also adversely affect nonplant products. In general, articles
with a high sulfur content may develop “off-odors” on contact with
MB. In some commodities the odors are difficult or impossible to
remove by aeration. If possible or practical, remove from the area to be
fumigated any items that are likely to develop an undesirable odor.
Ordinarily, the following items should not be fumigated:
◆ Any commodity which is not listed on the label or lacks a FIFRA
Section 18 Exemption
◆ Any commodity which lacks a treatment schedule
◆ Automobiles
◆ Baking powder
◆ Blueprints
◆ Bone meal
◆ Butter, lard, or fats, unless in airtight containers
◆ Charcoal (highly sorptive)
◆ Cinder blocks or mixed concrete and cinder blocks
◆ Electronic equipment
◆ Feather pillows
◆ Felt
◆ Furs
◆ High protein flours (soybean, whole wheat, peanut)
◆ Horsehair articles
◆ Leather goods, particularly kid leather
◆ Machinery with milled surfaces
◆ Magazines and newspapers (made of wood pulp)
◆ Magnesium articles (subject to corrosion)
◆ Paper with high rag or sulfur content
◆ Photographic chemicals and prints (not camera film or X-rays)
◆ Natural rubber goods, particularly sponge rubber, foam rubber,
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