210
Gene R. DeFoliart
appears to be associated with the bacterial cell at the outset of sporulation;
treatment that kills the cells but not the spores reduces toxicity (Davidson and
Singer, 1973). Singer (1975a) reported that strain SSl1-1, isolated from larvae
collected in Delhi, India, was 1000 times more active than previously examined
strains. It was more toxic to Culex spp. than to Ae. aegypti and Anopheles sp.
(Singer, 1975b). Strains 1593-4 from Indonesia and 1404-9 from the Philippines
were toxic to Culex and more toxic to Anopheles than had been demonstrated
by SSl1-1 in the earlier investigation (Singer and Murphy, 1976). Psorophora
columbiae and Culex nigripalpus have been shown susceptible to all three strains
(Ramoska et al., 1977).
In a field test against C. nigripalpus larvae, in which a mixture of the three
strains was applied, the 48 hr posttreatment reduction was 89%, with fourth
instars exhibiting lower susceptibility than earlier instars (Ramoska et al., 1978).
In two tests against P. columbiae in which the broods are more synchronous,
strain 1593 produced 100% mortality within 30 and 48 hr posttreatment.
8.6.4. Fungi
In Coelomomyces spp. host specificity is high (Federici et al., 1975, and
others) so several species have been chosen for development in the WHO testing
program. High temporary infection rates, from 59% to more than 95%, have
been observed in natural popUlations: Co. indicus in Anopheles gambiae 95% +
(Muspratt, 1962); Co. punctatus in An. quadrimaculatus up to 81 % (Umphlett,
1968); up to 80% + in Louisiana (Chapman et al., 1967); Co. punctatus and
Co. dodgei up to 67% and 59%, respectively, in An. crucians (Chapman and
Glenn 1972); Coelomomyces sp. in An. gambiae up to 77% (Service, 1973),
and infection may prolong the larval stage thus increasing susceptibility to other
mortality factors (Umphlett; 1970). The sporangium survives in dry mud, enabling recycling year after year in the mosquito environment (Roberts, 1967); 5
years after introduction of Co. stegomyiae on the Tokelau Islands, 37% of Ae.
polynesiensis and Ae. vexans nocturnus larvae sampled were parasitized (Laird,
1967).
The greatest obstacle to the eventual commercial development of Coelomomyces is that it is an obligate parasite requiring an alternation of hosts. Mass
production can be achieved in the laboratory (Couch, 1972) but only by duplicating the cycle that involves both a mosquito and the intermediate host, usually
a copepod (Federici and Roberts, 1976; Whisler et al., 1974, 1975). As to
mammalian safety of using Coelomomyces, no systematic tests have yet been
conducted (WHO, 1977).
M etarrhizium anisopliae can be mass propagated by industrial fermentation
and infects mosquito larvae when the asexual conidia are introduced into the
larval habitat. In vitro, the fungus mycelium produces destruxins A and B, which
Gene R. DeFoliart
appears to be associated with the bacterial cell at the outset of sporulation;
treatment that kills the cells but not the spores reduces toxicity (Davidson and
Singer, 1973). Singer (1975a) reported that strain SSl1-1, isolated from larvae
collected in Delhi, India, was 1000 times more active than previously examined
strains. It was more toxic to Culex spp. than to Ae. aegypti and Anopheles sp.
(Singer, 1975b). Strains 1593-4 from Indonesia and 1404-9 from the Philippines
were toxic to Culex and more toxic to Anopheles than had been demonstrated
by SSl1-1 in the earlier investigation (Singer and Murphy, 1976). Psorophora
columbiae and Culex nigripalpus have been shown susceptible to all three strains
(Ramoska et al., 1977).
In a field test against C. nigripalpus larvae, in which a mixture of the three
strains was applied, the 48 hr posttreatment reduction was 89%, with fourth
instars exhibiting lower susceptibility than earlier instars (Ramoska et al., 1978).
In two tests against P. columbiae in which the broods are more synchronous,
strain 1593 produced 100% mortality within 30 and 48 hr posttreatment.
8.6.4. Fungi
In Coelomomyces spp. host specificity is high (Federici et al., 1975, and
others) so several species have been chosen for development in the WHO testing
program. High temporary infection rates, from 59% to more than 95%, have
been observed in natural popUlations: Co. indicus in Anopheles gambiae 95% +
(Muspratt, 1962); Co. punctatus in An. quadrimaculatus up to 81 % (Umphlett,
1968); up to 80% + in Louisiana (Chapman et al., 1967); Co. punctatus and
Co. dodgei up to 67% and 59%, respectively, in An. crucians (Chapman and
Glenn 1972); Coelomomyces sp. in An. gambiae up to 77% (Service, 1973),
and infection may prolong the larval stage thus increasing susceptibility to other
mortality factors (Umphlett; 1970). The sporangium survives in dry mud, enabling recycling year after year in the mosquito environment (Roberts, 1967); 5
years after introduction of Co. stegomyiae on the Tokelau Islands, 37% of Ae.
polynesiensis and Ae. vexans nocturnus larvae sampled were parasitized (Laird,
1967).
The greatest obstacle to the eventual commercial development of Coelomomyces is that it is an obligate parasite requiring an alternation of hosts. Mass
production can be achieved in the laboratory (Couch, 1972) but only by duplicating the cycle that involves both a mosquito and the intermediate host, usually
a copepod (Federici and Roberts, 1976; Whisler et al., 1974, 1975). As to
mammalian safety of using Coelomomyces, no systematic tests have yet been
conducted (WHO, 1977).
M etarrhizium anisopliae can be mass propagated by industrial fermentation
and infects mosquito larvae when the asexual conidia are introduced into the
larval habitat. In vitro, the fungus mycelium produces destruxins A and B, which