Environmental Engineering Reference
In-Depth Information
pesticide active ingredients registered with the EPA, which include 18 floral attractants,
20 plant growth regulators, 6 insect growth regulators, 19 repellents, and 36 pheromones
(Steinwand 2008).
19.10.1 Semiochemicals
Semiochemicals (Gk. semeion , a signal) are chemicals that mediate interactions between
organisms. Semiochemicals are subdivided into allelochemicals or pheromones depend-
ing on whether the interactions are interspecific or intraspecific, respectively (Anonymous
1981). Allelochemicals are chemicals that are significant to individuals of a species dif-
ferent from the source species. They are subdivided into several groups depending on
whether the response of the receiver is adaptively favorable to the emitter but to not the
receiver (allomones), is favorable to the receiver but not to the emitter (kairomones), or is
favorable to both the emitter and the receiver (synomones). Within both allelochemicals
and pheromones, it is sometimes useful to refer to chemicals as arrestants, attractants,
repellents, deterrents, stimulants, or other descriptive terms. These terms can indicate
what behavior is involved in the response such as a feeding stimulant or flight arrestant.
19.10.2 Insect Pheromones
Insect pheromones are chemicals used by an insect to communicate with other members
of the same species. Structurally these chemicals are often very similar to substances
used in flavors and fragrances. The insect pheromones themselves do not kill a target
pest. When used for pest management, two common uses are to attract an insect to a
trap containing a lethal pesticide or to disrupt mating. With mating disruption, propor-
tionately large concentrations of the sex pheromones are present in the air, thus confus-
ing the males and decreasing their success rate at locating a female with which to mate.
Pheromones can also be used to monitor pest populations as part of larger integrated pest
management (IPM) systems, particularly to determine appropriate timing and applica-
tion of pesticides. Insect pheromones account for a large percentage of the biochemical
pesticides on the market. In mid-2002, EPA had registered 36 pheromones, which com-
prised over 200 individual products (Ware and Whitacre 2004). Insect sex pheromones
can be used alone to manage pest populations when pest pressure is moderate to low,
such as after several years of consecutive use. Other practical uses include “in survey
traps to provide information about population levels, to delineate infestations, to moni-
tor control or eradication programs, and to warn of new pest introductions” (Ware and
Whitacre 2004).
Advantages to the use of insect pheromones include their high species specificity and
relatively low toxicity. Sex pheromones tend to be specific to a particular species or even
strain of insect, making them one of the most targeted pest management strategies. This
specificity thus maintains an ecological balance by leaving undisturbed populations of
other insect species and nontarget organisms.
A disadvantage of insect pheromones is that they often must be used in combination
with other pest management strategies to achieve the efficacy desired. This is particularly
true when pest pressure is high. With high pest pressure, the male is more likely to locate
a mate by simply bumping into the female rather than by using pheromones to commu-
nicate over long distances. However, the combination of pest management strategies typi-
cally lowers the pest pressure in subsequent years, creating the opportunity for the insect
pheromones to be used alone.
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