Insect Control: Biological and Synthetic Agents - Index of

294 8: Mosquitocidal B. sphaericus: Toxins, Genetics, Mode of Action, Use, and Resistance Mechanisms
8.4. Field Use of B. sphaericus
Due to the special properties of mosquitocidal Bti
and B. sphaericus (e.g., environmental safety, high
specificity of B. sphaericus and Bti toxins, relative
ease of mass production, formulation and application,
suitability for integrated control programs,
and relatively low cost for development and registration),
these bacilli were rapidly developed
and used in many mosquito and/or black fly control
programs. Bti has a broader application because
unlike B. sphaericus it also has larvicidal activity
against important vectors belonging to the Aedes
and Simulium genera. B. sphaericus has been used
to control C. pipiens and C. quinquefasciatus
larvae since the late 1980s, and it is also used to
control Anopheles spp. in some areas (Table 3;
Karch et al., 1992; Hougard et al., 1993; Kumar
et al., 1994). Even though the larvicidal activity of
B. sphaericus is mainly restricted to Culex and
Anopheles species, it is stable, can recycle in organically
polluted water (major breeding sites of Culex
species), and is highly persistent (Lacey et al., 1987;
Correa and Yousten, 1995), giving it an advantage
over Bti. Both B. sphaericus and Bti overcome the
resistance of Culex and Anopheles to conventional
insecticides.
In temperate regions, B. sphaericus is mainly
used to reduce nuisance due to mosquito bites. It
has been used on a large scale in Germany, especially
in the Rhine Valley (Becker, 2000), and in France,
where it was used to control C. pipiens (resistant
to the organophosphate insecticide temephos) on
the Mediterranean coast for more than 7 years
before any problems of resistance arose (Sinègre
et al., 1993). However, the main interest (amount
of product used and treated areas) is in tropical
regions where B. sphaericus is used to control
Culex and Anopheles populations, particularly to
reduce the incidence of vector-born diseases like
filariasis and malaria. In Goa (India), the use of
B. sphaericus against A. stephensi larvae resulted
in a notable reduction in the number of cases of
malaria (Kumar et al., 1994). This was also the
case in China against A. sinensis (Becker, 2000;
Yuan et al., 2000). In the Democratic Republic of
Congo, successful experimental field trials were run
against A. gambiae in rice fields (Karch et al., 1992).
C. quinquefasciatus populations were reduced in
the town of Maroua in Cameroon (Barbazan et al.,
1997). In the city of Recife, in Brazil, the experimental
application of B. sphaericus successfully reduced
the number of cases of filariasis by reducing the
adult vector population of C. quinquefasciatus
(Regis et al., 1995). Table
3 Examples of large-scale field use of Bacillus sphaericus against mosquito populations and the development of resistance
References
B. sphaericus
strain Treatment frequency Treatment period Treated area Locality/country Resistance RR a
Target species
A. stephensi B-101 Weekly 9 months 2 km 2
Panaji city (India) Kumar et al. (1996)
C. pipiens 2362 Every 21 days to 6 months 7 years 210 villages Mediterranean Coast >20 000
(France)
b Sine` gre et al. (1993, 1994)
C. quinquefasciatus 2362 Monthly/fortnightly 26 months 1.2 km 2
Recife city (Brazil) 10 Silva–Filha et al. (1995)
C. quinquefasciatus 1593M Fortnightly 2 years 8 km 2
Kochi (India) 146 Rao et al. (1995)
C. quinquefasciatus C3-41 3 times a month 8 years 8 km 2
Dongguan city (China) 22 000 Yuan et al. (2000)
C. quinquefasciatus 2362 Every 3 months 4 years 200 ha Yaounde´ (Cameroon) Hougard et al. (1993)
C. quinquefasciatus 2362 Twice a year 2 years 2000 ha Maroua (Cameroon) Barbazan et al. (1997)
a The level of resistance is calculated as the ratio of the LC50 values of the resistant population to that of susceptible laboratory colonies.
bAt isolated breeding sites.
, resistance ratio value not reported.