NAVMED P-5010-8 - Navy Medicine - U.S. Navy
NAVMED P-5010-8 - Navy Medicine - U.S. Navy
NAVMED P-5010-8 - Navy Medicine - U.S. Navy
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8-11 CHAPTER 8. NAVY ENTOMOLOGY AND PEST CONTROL TECHNOLOGY 8-12<br />
d. Pesticide Dispersal. After the desired<br />
formulations have been selected, prepared, and<br />
procured, they may be dispersed in the following<br />
forms:<br />
(1) Gases and Vapors. The dispersal<br />
of gases and vapors is termed fumigation. They<br />
must be handled with great care and only under<br />
direct supervision of specially trained and<br />
certified personnel. Gases and vapors are able to<br />
penetrate packaged commodities, clothing and<br />
structures, which are inaccessible to treatment<br />
by other dispersal methods. Because they lack<br />
residual properties, fumigants are used when<br />
other formulations are ineffective or because of<br />
penetration requirements. However, because of<br />
their physical properties, fumigants can be used<br />
only in airtight spaces, which prevent dissipation.<br />
One type of fumigation, known as<br />
"vaporization," is accomplished by the use of<br />
solids such as paradichlorobenzene (PDB),<br />
which at room temperatures, passes from a solid<br />
directly into a vapor (sublimation).<br />
(2) Aerosols. Aerosols are defined as<br />
a suspension of liquid or solid particles in air<br />
where the particle size generally ranges from 0.1<br />
to 50 microns in diameter with 80% of the<br />
particles in the 0.1 to 30 micron range. Liquid<br />
particles make up a fog and solid particles form<br />
a smoke. Insecticide aerosols are frequently<br />
dispensed from hand held pressurized containers<br />
or larger ultra low volume (ULV) dispersal<br />
equipment.<br />
(3) Mists. Mists are dispersed<br />
particles in which the particles are intermediate<br />
in size between those of aerosols and fine<br />
sprays. Droplets in the 50 to 100 micron size<br />
range are considered to be mists. They are less<br />
effective than aerosols for outside space<br />
treatment, but they are adaptable for larviciding<br />
in areas accessible to vehicles and for large scale<br />
residual spraying of vegetation. Because of their<br />
larger size, mists can be used under a wider<br />
range of weather conditions than can aerosols,<br />
and their residual effect is greater.<br />
(4) Sprays. (The most commonly<br />
used formulation.)<br />
(a) Fine sprays. Fine spray<br />
droplets are considered to be from 100 to 400<br />
microns in diameter. Droplets within this range<br />
remain airborne short periods of time and settle<br />
rapidly. Sprays of this type are frequently used<br />
as mosquito larvicides and for residuals.<br />
(b) Coarse sprays. These sprays<br />
consist of droplets over 400 microns in diameter<br />
and are applied evenly to wet a surface. Coarse<br />
sprays are frequently employed when using<br />
herbicides and when applying heavy residuals of<br />
insecticide to fly breeding areas.<br />
8-12. Application of Pesticides<br />
a. Effects of Particle Size. Efficient<br />
application of pesticides requires the dispersal of<br />
the proper particle size for the type of<br />
application desired. The residual quality of<br />
many insecticides makes it possible to kill by<br />
contact long after the material has been applied<br />
to walls, vegetation or other insect resting<br />
places. In order to take full advantage of the<br />
residual characteristics of a pesticide, it should<br />
be applied only in the form of a coarse spray or<br />
dust. By contrast, efficient use of space sprays<br />
calls for their dispersal in much smaller<br />
particles. Coarse sprays are inefficient aerosols<br />
because the fewer number of droplets decreases<br />
the chances of target contact. Those particles,<br />
which do contact the target, may contain many<br />
times the amount of insecticide needed to affect<br />
a kill. Large particles fall to the ground while<br />
small particles may remain airborne for<br />
extended periods of time, providing more<br />
opportunity to contact targets. In this respect<br />
there is also a disadvantage in that unfavorable<br />
air current or high wind velocity may cause<br />
rapid dispersal of the droplets into the<br />
atmosphere, and the small insecticide particles<br />
may be transported to non-target areas. Under<br />
favorable conditions, aerosols or fogs are quite<br />
efficient for killing insects or other arthropods<br />
by means of space treatment.<br />
9 Nov 2004<br />
8-11