September/October 2017

site-specific, pre-application record of
intended use). Like MITC generators,
AITC may exhibit slow movement in the
soil, suggesting that its use for perennial
crops may need more research to optimize
its utility in scenarios having larger
soil volumes that need to be treated. Like
other materials, AITC could be used in
crop termination, whereby application
is done after final harvest to ‘burn down’
the roots and reduce pathogen pressure
before the crop residue is tilled under for
decomposition. Although AITC product
labels have generally less restrictive
requirements than the traditional fumigants,
its application does entail the use
of proper PPE due to corrosiveness and
skin irritation potential. This should not
deter from use if high efficacy rates can
be shown. Registration of this material
was granted federally several years ago,
and is currently registered in 27 different
states. Registration in California is
pending.
Another material used commercially
in some US states is dimethyl disulfide
(DMDS), formulated as Paladin
or Paladin EC. Outside of agriculture,
DMDS is primarily used as catalyst
in hydrocarbon processing. Its acute
toxicity and other exposure effects are
such that it is considered reasonably safe
to use. In fact, low doses of this material
are used as food additives to impart
a pungent garlic odor. However, at
elevated concentrations, this same odor
can be highly objectionable, and so it is
regulated based on its potential to be an
odor nuisance. DMDS soil fumigation
product labels currently mandate the use
of low-permeability tarps for mitigation
of the odor of this effective nematicide,
Aqueous cyanamide formulations at
10 and 50 percent a.i., fall into Pesticide
Categories III or II, respectively,
and constitute a candidate for biocidal
treatments. For tree and vine crops,
this non-fuming, non-odorous, highly
water soluble biocide will be tree site or
strip applied and further diluted 250 to
500-fold to reach 99 percent of the target
sites. The active ingredient metabolizes
in a cascade of nitrogenous materials
within soil but is also adequately systemic
to kill live roots, endoparasitic life
stages of nematodes within and plant
tissues above. It does not penetrate well
into dead plant tissues. Application rates
and introduction of nitrogen amounts
still need to be worked out and will likely
vary for different crops and soil textures.
This liquid is currently available globally
as a plant growth regulator under several
brand names. It is also commercialized
for its lethal actions upon enzymes,
which may explain plant responses
that are visibly more complex than just
an overdose of nitrogen. This solution
is well-suited for use in replant problem
sites for the so-called “Starve and
Switch” strategy, meaning the reduction
of pathogenic organisms of a particular
crop and the following change to
different crop genetics. The commercial
development of such formulations is at
its beginning.
A quite different material currently
under experimental exploration is
ethanedinitrile (EDN). This material
has a lower boiling point and a higher
vapor pressure than methyl bromide.
At ambient temperature it is a gas, and
thus requires pressurized handling and
potentially novel application equipment.
EDN has a short half-life in soil.
Current research is focused on safe and
uniform application, and improving its
residence time in soil. Crop trials have
shown its potential to be a broad-spectrum
fumigant.
In summary, in the “post methyl
bromide era”, the older, and proven,
chemistries like 1,3-D, chloropicrin,
and the MITC generators are in high
demand, and are often used in various
combinations; while newer chemistries
undergo optimization as methyl bromide
alternatives. Work on these newer materials
is ongoing, where adjustments and
technical advancements may be required
before some of them can be widely
used. Overall, the concept of a “drop-in
replacement” for methyl bromide very
likely needs to be shelved, as agricultural
production converts to the concept of
Integrated Pest Management, i.e., the use
of multiple pest control strategies and
tactics for the management of soil-borne
maladies for high-value crop production.
Comments about this article? We want
to hear from you. Feel free to email us at
article@jcsmarketinginc.com
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September/October 2017
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