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Phytosanitary Measures to Prevent the Introduction of Invasive Species 381
destructor, and cereal leaf beetle, Oulema melanopus, in baled hay shipped
from the US to Japan and Canada (Yokoyama and Miller 2002, 2003). Cleaning
and inspection may be used to remove surface pests. Cherimoya and limes
from Chile may be washed and waxed as a phytosanitary treatment for the
mite Brevipalpus chilensis for export to the US.
21.3.2.11 Researched but not yet Applied Treatments
Considerable research has been carried out on a number of phytosanitary
treatment possibilities that have not yet reached commercial application
(Hallman 2002). Atmospheres with very little oxygen and high levels of carbon
dioxide have been used successfully to disinfest commodities of pests.
One successful trial shipment of asparagus, held for 4.5 days at 0–1 °C and
60 % CO 2 to disinfest it of aphids and thrips, was exported from New Zealand
to Japan (Carpenter and Potter 1994).
Low oxygen/high carbon dioxide treatments combine well with elevated
temperatures. For example, diapausing spider mites, Tetranychus urticae,
were killed in one-seventh of the time at 40 °C when treated in an atmosphere
of 0.4 % O 2 and 20 % CO 2 , compared with ambient atmosphere (Whiting and
van den Heuvel 1995). Low oxygen/high carbon dioxide phytosanitary treatment
research is frequently carried out at low temperatures, and often it is the
low temperature alone, with apparently no benefit from the modified atmosphere,
that causes pest mortality (Hallman 1994).
Radiofrequency heating has been researched as a phytosanitary treatment
since the late 1920s, with no commercial application yet (Hallman 2002). The
potential benefits are that radiofrequency could heat a commodity uniformly,
as opposed to heated air and water that heat from the outside in, and that
radiofrequency could heat commodities rapidly, in a matter of seconds and as
part of a conveyor line, rather than during 1 to many hours per batch load, as
is done with heated air and water. In practice, radiofrequency heating has had
problems with uniformity when heating fresh produce. The drier nature of
nuts and dried fruit might offer an advantage to radiofrequency heating, as
this type of heating selectively heats water; thus, moist insects inside of dry
products might be selectively heated (Wang et al. 2001).
21.4 Future Challenges
To satisfy the demand for world trade in products quarantined because of
invasive species as well as reduce the temptations to smuggle these products,
improvements in the efficacy, ease of application, and cost of phytosanitary
methods should be sought. Because methyl bromide fumigation is a key phy-