202
Gene R. DeFoliart
alent to that obtained by larviciding (Axtell, 1970a). It was estimated that larviciding requires about five times as much insecticide and two and one-half times
as many man-hours as required for the integrated program (Axtell, 1970b).
It would be nice to end the story there, as an example of a complete success
for integrated control. However, in the attempted management of wild populations solutions seldom prove to be simple or final. Axtell and Edwards (1970)
and others have reported the failure of house flies to develop in the presence of
the soldier fly, H ermetia illucens, because the latter make manure physically
unsuitable for housefly development. However, the soldier flies themselves may
become a nuisance, and since they are not satisfactorily reduced by the integrated
method, a decision is sometimes necessary as to whether a larvicide should be
applied for their control. Such a decision must be made with care as the larvicide
application decimates the mite populations and commits the producer to a single
course of action-continued larviciding for the remainder of the season to control
house flies.
In contrast to the North Carolina program, the work of Hoy and colleagues
on rice field mosquito control in California is instructive as to how the introduction of a new. component can disrupt effective natural control. Hoy et al.
(1971) concluded that in rice fields, of which there are more than 400,000 acres
in California, reasonable control of C. tarsalis and An. freeborni could be achieved
by early-season stocking of Gambusia affinis at the rate of 300 mature females
per acre. In a later test (Hoy et al., 1972), however, they compared two fishstocking rates (0.2 and 0.6Ib/acre) and chlorpyrifos (0.0125 lb*/acre) and found
that the fields stocked at the higher rate of fish did not produce significantly
fewer mosquitoes than the untreated fields. The authors attributed the poor results
to disruption of notonectids and other invertebrate predators. The mosquito population in the fields sprayed with chlorpyrifos surged to several times greater
than that found in the undisturbed control fields. The relatively low numbers of
larvae in the control fields also suggested the presence of an effective invertebrate
predator population.
As these results illustrate, we still do not know, in most cases, what degree
of control is contributed by indigenous natural control agents. While waiting for
the development of new more selective insecticides and other biocides usable
as inundation techniques, much more research is needed on the ecology and
behavior of native fishes, predatory Hemiptera, Coleoptera, and other invertebrates and pathogens that share the habitats of vector and pest targets.
The preceding example also suggests that, as more integrated programs
* Throughout this chapter, insecticide application rates are stated as amounts of actual ingredient
applied.
Gene R. DeFoliart
alent to that obtained by larviciding (Axtell, 1970a). It was estimated that larviciding requires about five times as much insecticide and two and one-half times
as many man-hours as required for the integrated program (Axtell, 1970b).
It would be nice to end the story there, as an example of a complete success
for integrated control. However, in the attempted management of wild populations solutions seldom prove to be simple or final. Axtell and Edwards (1970)
and others have reported the failure of house flies to develop in the presence of
the soldier fly, H ermetia illucens, because the latter make manure physically
unsuitable for housefly development. However, the soldier flies themselves may
become a nuisance, and since they are not satisfactorily reduced by the integrated
method, a decision is sometimes necessary as to whether a larvicide should be
applied for their control. Such a decision must be made with care as the larvicide
application decimates the mite populations and commits the producer to a single
course of action-continued larviciding for the remainder of the season to control
house flies.
In contrast to the North Carolina program, the work of Hoy and colleagues
on rice field mosquito control in California is instructive as to how the introduction of a new. component can disrupt effective natural control. Hoy et al.
(1971) concluded that in rice fields, of which there are more than 400,000 acres
in California, reasonable control of C. tarsalis and An. freeborni could be achieved
by early-season stocking of Gambusia affinis at the rate of 300 mature females
per acre. In a later test (Hoy et al., 1972), however, they compared two fishstocking rates (0.2 and 0.6Ib/acre) and chlorpyrifos (0.0125 lb*/acre) and found
that the fields stocked at the higher rate of fish did not produce significantly
fewer mosquitoes than the untreated fields. The authors attributed the poor results
to disruption of notonectids and other invertebrate predators. The mosquito population in the fields sprayed with chlorpyrifos surged to several times greater
than that found in the undisturbed control fields. The relatively low numbers of
larvae in the control fields also suggested the presence of an effective invertebrate
predator population.
As these results illustrate, we still do not know, in most cases, what degree
of control is contributed by indigenous natural control agents. While waiting for
the development of new more selective insecticides and other biocides usable
as inundation techniques, much more research is needed on the ecology and
behavior of native fishes, predatory Hemiptera, Coleoptera, and other invertebrates and pathogens that share the habitats of vector and pest targets.
The preceding example also suggests that, as more integrated programs
* Throughout this chapter, insecticide application rates are stated as amounts of actual ingredient
applied.