Thus, it is frequently desirable to chemically rid the water of its flora. It is only as
a last resort that chemical control of aquatic weeds is employed, however, and then
only after approval by the proper local, state, or federal agency. Weed killers, such as
2,4-D, applied as pellets or granules, are effective for rooted plants, whereas spray
application is effective for floating weeds. Copper sulfate should not be used for
aquatic weeds, since the concentration required to destroy the vegetation will most
certainly kill any fish in the vicinity. Copper sulfate is, however, commonly used for
the control of algae.
It should be pointed out that a chemical control program is best done with
complete knowledge of the system being treated. The chemistry of the water and
its physical characteristics will contribute to the success or failure of the program.
For example, it is known that CuSO 4 is rapidly inactivated in alkaline hard water by
precipitation as the basic carbonate, and that fish kill can occur as readily from
asphyxiation as from toxicity following a CuS04 treatment. Decomposition of algae
with the concomitant consumption of oxygen may exhaust the oxygen supply
producing such a massive fish kill, especially when the water temperature is high.
Thus, for an effective program, investigation is highly warranted before chemical
application.
7.3 Arthropods
The mention of mosquitoes and houseflies both as nuisances and disease vectors is
well justified and certainly few will contest this double entry.
More than an annoyance, termites are highly destructive and impose serious
restraints in building construction. Redwood and certain species of cedar are quite
resistant to termites, whereas pine and fir are readily attacked under certain conditions. There are both above-ground and below-ground types of termites. Belowground termites are very sensitive to light and moisture and, consequently, protection is best achieved through lighting and ventilating subterranean areas.
Above-ground termites may be of the damp wood or dry wood destroying type.
The dry wood type, along with other nuisance insects (such as roaches, fleas,
bedbugs, and ants), is quite susceptible to sorptive dusts such as silica gels. These
materials remove the lipoid protective layer covering the insect’s body and cause a
rapid loss of water and death. Both types are controlled with pentachlorophenol, as
well as a wide range of other insecticides, including lindane, chlordane, and dieldrin.
Several newer termiticides, such as bifrenthin, deltamethrin, fipronil, and others, are
undergoing testing.
Ants can be a serious problem, but have the beneficial effect of controlling
termites by entering their tunnels and attacking them. Where ants are to be controlled, chlordane has been most effective, but malathion or diazinon has also been
useful.
Pediculosis or infestation with lice can be controlled by dusting with insecticidal
powders.
10 Environmental Control of Pests and Vectors
403
a last resort that chemical control of aquatic weeds is employed, however, and then
only after approval by the proper local, state, or federal agency. Weed killers, such as
2,4-D, applied as pellets or granules, are effective for rooted plants, whereas spray
application is effective for floating weeds. Copper sulfate should not be used for
aquatic weeds, since the concentration required to destroy the vegetation will most
certainly kill any fish in the vicinity. Copper sulfate is, however, commonly used for
the control of algae.
It should be pointed out that a chemical control program is best done with
complete knowledge of the system being treated. The chemistry of the water and
its physical characteristics will contribute to the success or failure of the program.
For example, it is known that CuSO 4 is rapidly inactivated in alkaline hard water by
precipitation as the basic carbonate, and that fish kill can occur as readily from
asphyxiation as from toxicity following a CuS04 treatment. Decomposition of algae
with the concomitant consumption of oxygen may exhaust the oxygen supply
producing such a massive fish kill, especially when the water temperature is high.
Thus, for an effective program, investigation is highly warranted before chemical
application.
7.3 Arthropods
The mention of mosquitoes and houseflies both as nuisances and disease vectors is
well justified and certainly few will contest this double entry.
More than an annoyance, termites are highly destructive and impose serious
restraints in building construction. Redwood and certain species of cedar are quite
resistant to termites, whereas pine and fir are readily attacked under certain conditions. There are both above-ground and below-ground types of termites. Belowground termites are very sensitive to light and moisture and, consequently, protection is best achieved through lighting and ventilating subterranean areas.
Above-ground termites may be of the damp wood or dry wood destroying type.
The dry wood type, along with other nuisance insects (such as roaches, fleas,
bedbugs, and ants), is quite susceptible to sorptive dusts such as silica gels. These
materials remove the lipoid protective layer covering the insect’s body and cause a
rapid loss of water and death. Both types are controlled with pentachlorophenol, as
well as a wide range of other insecticides, including lindane, chlordane, and dieldrin.
Several newer termiticides, such as bifrenthin, deltamethrin, fipronil, and others, are
undergoing testing.
Ants can be a serious problem, but have the beneficial effect of controlling
termites by entering their tunnels and attacking them. Where ants are to be controlled, chlordane has been most effective, but malathion or diazinon has also been
useful.
Pediculosis or infestation with lice can be controlled by dusting with insecticidal
powders.
10 Environmental Control of Pests and Vectors
403