196
Gene R. DeFoliart
and the current status of insecticide resistance in the two states. Historically,
there have been some parallels in control strategies and also some differences,
the latter being in part dictated by the differing nature of the mosquito problem
in the two states.
In coastal Florida, the salt marsh breeders, Aedes taeniorhynchus and Ae.
sollicitans have posed a serious threat to tourism and retirement. In the interior,
the glades mosquito, Psorophora confinnis, breeds in vast areas of poorly drained
flatwoods as well as in irrigated pastures and citrus groves. In California, the
main problem stems from freshwater mosquitoes Ae. nigromaculis and Ae. dorsalis in irrigated pastures and other irrigated agricultural lands, abetted by Culex
tarsalis and Anopheles freeborni, mainly in rice fields.
Both states have utilized source reduction, but Florida has fewer options
in this respect. Its mosquitoes come from wildlands, and despite Provost's belief
(1977) that salt marshes can be altered without ecological damage, salt marsh
alterations have met with increasing opposition from environmentalists. In the
case of Psorophora, the sheer dispersion and vastness of the breeding grounds
preclude much effort at source reduction. For the same reasons that source
reduction options are limited in Florida, larvicides would have limited utility.
By contrast, California's mosquito problems are mostly man-made, thus more
amenable to correction through prevention or, lacking prevention, the use of
larvicides.
Chemical names of insecticides are listed in Table 8.1. Table 8.2 compares
the use of mosquito insecticides in Florida and California, 1970-1972. Despite
early exhortations by Herms (1949) and others for restraint in the use of larvicides
and for continued emphasis on prevention, by 1954 resistance to all chlorinated
hydrocarbons was widespread in California, and by 1970 mosquito control was
in a state of crisis with Ae. nigromaculis and C. tarsalis widely resistant to all
registered organophosphorous (OP) compounds. Note in Table 8.2 the decline
in OP larvicides from 227,000 lb to only 98,000 lb in the 2-year period from
1970 to 1972. This decrease was made up for by an increase in the use of
larvicidal oils. The resistance situation in California rendered it extremely vulnerable if the VEE invasion of Texas in 1972 had spread to that state. Fortunately,
the virus was stopped in Texas.
In Florida, because of the nature of the mosquito production grounds, and
in a conscious effort to delay the appearance of resistance, the State Board of
Health advised mosquito control districts to use organic insecticides only against
adults, not against larvae, the rationale being that a thorough-going larvicide
program selects for tolerance against the entire population while adulticiding
exerts pressure only against the segment of the mosquito population that finds
its way to urban areas. Note (Table 8.2) that Florida used 848,000 lb of adulticides
in 1972 compared to 8000 lb by California and that, except for larvicidal oils
Gene R. DeFoliart
and the current status of insecticide resistance in the two states. Historically,
there have been some parallels in control strategies and also some differences,
the latter being in part dictated by the differing nature of the mosquito problem
in the two states.
In coastal Florida, the salt marsh breeders, Aedes taeniorhynchus and Ae.
sollicitans have posed a serious threat to tourism and retirement. In the interior,
the glades mosquito, Psorophora confinnis, breeds in vast areas of poorly drained
flatwoods as well as in irrigated pastures and citrus groves. In California, the
main problem stems from freshwater mosquitoes Ae. nigromaculis and Ae. dorsalis in irrigated pastures and other irrigated agricultural lands, abetted by Culex
tarsalis and Anopheles freeborni, mainly in rice fields.
Both states have utilized source reduction, but Florida has fewer options
in this respect. Its mosquitoes come from wildlands, and despite Provost's belief
(1977) that salt marshes can be altered without ecological damage, salt marsh
alterations have met with increasing opposition from environmentalists. In the
case of Psorophora, the sheer dispersion and vastness of the breeding grounds
preclude much effort at source reduction. For the same reasons that source
reduction options are limited in Florida, larvicides would have limited utility.
By contrast, California's mosquito problems are mostly man-made, thus more
amenable to correction through prevention or, lacking prevention, the use of
larvicides.
Chemical names of insecticides are listed in Table 8.1. Table 8.2 compares
the use of mosquito insecticides in Florida and California, 1970-1972. Despite
early exhortations by Herms (1949) and others for restraint in the use of larvicides
and for continued emphasis on prevention, by 1954 resistance to all chlorinated
hydrocarbons was widespread in California, and by 1970 mosquito control was
in a state of crisis with Ae. nigromaculis and C. tarsalis widely resistant to all
registered organophosphorous (OP) compounds. Note in Table 8.2 the decline
in OP larvicides from 227,000 lb to only 98,000 lb in the 2-year period from
1970 to 1972. This decrease was made up for by an increase in the use of
larvicidal oils. The resistance situation in California rendered it extremely vulnerable if the VEE invasion of Texas in 1972 had spread to that state. Fortunately,
the virus was stopped in Texas.
In Florida, because of the nature of the mosquito production grounds, and
in a conscious effort to delay the appearance of resistance, the State Board of
Health advised mosquito control districts to use organic insecticides only against
adults, not against larvae, the rationale being that a thorough-going larvicide
program selects for tolerance against the entire population while adulticiding
exerts pressure only against the segment of the mosquito population that finds
its way to urban areas. Note (Table 8.2) that Florida used 848,000 lb of adulticides
in 1972 compared to 8000 lb by California and that, except for larvicidal oils