212
Gene R. DeFoliart
There are indications that, despite the planned stage V testing in 1978 (Table
8.3), this species may be slow in progressing to commercial production. Spores
of good viability are produced in huge numbers in com earworms (Undeen and
Maddox, 1973; Undeen and Alger, 1975), but this in vivo method of production
is expensive. Improved formulations are needed, and there are unsettled questions
as to mammalian safety.
Two field tests have been encouraging. One, in Pakistan, resulted in infection of 50% of An. stephensi larvae. In field tests against An. albimanus in
Panama, infection rates were dose dependent, ranging from 16% in an area given
a single dose, to 86% in an area given four treatments.
8.6.6. Nematodes
Romanomermis culicivorax (= Reeseimermis nielseni) is the first mosquito
pathogen to be registered and marketed in the United States (Fairfax's Skeeter
Doom). Numerous field surveys and laboratory studies have demonstrated its
wide host range among mosquitoes (Chapman et al., 1969, 1970; Petersen,
1975; Petersen and Willis, 1971; Petersen et al., 1968, 1969), and its safety to
nontarget organisms (lgnoffo et al., 1973, and others). As yet, mass production
is only by in vivo methods developed at the USDA's Gulf Coast Mosquito
Research Laboratory at Lake Charles, Louisiana (Petersen, 1973a-c, 1978; Petersen and Willis, 1970, 1972a) ,
Field releases have given varied results depending on the mosquito species
and aquatic conditions pertaining (Brown et al., 1977; Hoy and Petersen, 1973;
Mitchell et al., 1972; Petersen and Willis, 1972b, 1974; Petersen et al., 1972,
1973). The largest and most recent test was conducted against An. albimanus
and An. pseudopunctipennis at Lake Apastepeque in EI Salvador (Petersen et
al., 1978a,b). The lake is about 2.5 km in circumference and the breeding habitat
is a 2- to 5-m band of marginal floating and surface vegetation extending around
nearly the entire margin. Eleven applications over a 7-week period reduced the
larval population by 94% by the end of the release period, although the average
parasitism during the release period was only 58%. In order to carry out the
planned treatment of 144,000 m 2 at a dosage rate of about 4800 preparasites per
square millimeter of surface area, a total of 14.1 lb of postparasitic nematodes
and 425 cultures (15 g) were produced. Five weeks after cessation of treatment,
larval populations had increased by more than three times.
Although the nematodes can sometimes establish and recycle (Petersen and
Willis, 1972b, 1975, and others), the incidence of infection is usually too low
for adequate control, so repeated applications are necessary. Also, as infected
larvae die before pupation (Petersen et al., 1969, and others), there is little
natural dispersion of the organisms.
Gene R. DeFoliart
There are indications that, despite the planned stage V testing in 1978 (Table
8.3), this species may be slow in progressing to commercial production. Spores
of good viability are produced in huge numbers in com earworms (Undeen and
Maddox, 1973; Undeen and Alger, 1975), but this in vivo method of production
is expensive. Improved formulations are needed, and there are unsettled questions
as to mammalian safety.
Two field tests have been encouraging. One, in Pakistan, resulted in infection of 50% of An. stephensi larvae. In field tests against An. albimanus in
Panama, infection rates were dose dependent, ranging from 16% in an area given
a single dose, to 86% in an area given four treatments.
8.6.6. Nematodes
Romanomermis culicivorax (= Reeseimermis nielseni) is the first mosquito
pathogen to be registered and marketed in the United States (Fairfax's Skeeter
Doom). Numerous field surveys and laboratory studies have demonstrated its
wide host range among mosquitoes (Chapman et al., 1969, 1970; Petersen,
1975; Petersen and Willis, 1971; Petersen et al., 1968, 1969), and its safety to
nontarget organisms (lgnoffo et al., 1973, and others). As yet, mass production
is only by in vivo methods developed at the USDA's Gulf Coast Mosquito
Research Laboratory at Lake Charles, Louisiana (Petersen, 1973a-c, 1978; Petersen and Willis, 1970, 1972a) ,
Field releases have given varied results depending on the mosquito species
and aquatic conditions pertaining (Brown et al., 1977; Hoy and Petersen, 1973;
Mitchell et al., 1972; Petersen and Willis, 1972b, 1974; Petersen et al., 1972,
1973). The largest and most recent test was conducted against An. albimanus
and An. pseudopunctipennis at Lake Apastepeque in EI Salvador (Petersen et
al., 1978a,b). The lake is about 2.5 km in circumference and the breeding habitat
is a 2- to 5-m band of marginal floating and surface vegetation extending around
nearly the entire margin. Eleven applications over a 7-week period reduced the
larval population by 94% by the end of the release period, although the average
parasitism during the release period was only 58%. In order to carry out the
planned treatment of 144,000 m 2 at a dosage rate of about 4800 preparasites per
square millimeter of surface area, a total of 14.1 lb of postparasitic nematodes
and 425 cultures (15 g) were produced. Five weeks after cessation of treatment,
larval populations had increased by more than three times.
Although the nematodes can sometimes establish and recycle (Petersen and
Willis, 1972b, 1975, and others), the incidence of infection is usually too low
for adequate control, so repeated applications are necessary. Also, as infected
larvae die before pupation (Petersen et al., 1969, and others), there is little
natural dispersion of the organisms.