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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 91, Num. 2, 1996, pp. 161-162
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Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(1), Mar/Apr 1996
RESEARCH NOTE: Biological Control of Aedes
albopictus (Diptera: Culicidae) Larvae in Trap Tyres by
Mesocyclops longisetus (Copepoda: Cyclopidae) in Two Field
Trials
Luciana Urbano Santos, Carlos Fernando S Andrade*/^+, Gilcia A
Carvalho*
Pos-Graduac o - Departamento de Parasitologia *Departamento de
Zoologia, Instituto de Biologia, Universidade Estatual de
Campinas, Caixa Postal 6109, 13083-970 Campinas, SP, Brasil
Code Number: OC96031
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[TABLES AND FIGURES AT END OF TEXT]
Key word: dengue - mosquito control - copepods
Cyclopid copepods have been evaluated and used in at least six
countries as biological control agents for container-breeding
Aedes larvae (GG Marten 1990 J Am Mosq Control Assoc
6: 681-688, B Kay et al. 1992 J Med Entomol 29: 599-
692). Three copepod species have received more attention:
Macrocyclops albidus, Mesocyclops aspericornis
and Mesocyclops longisetus. The last species has been
pointed out as the most effective not only due to its higher
voracity as a predator but also due to a best survival capacity
in the absence of mosquito larvae. Some control studies have been
carried out involving community participation in the distribution
of copepods (E Fernadez, R Soto 1991 J Am Mosq Control Assoc
7: 633-645). Moreover, some evaluations have revealed the
feasibility of spray applications of copepods through
conventional equipament (GG Marten 1991 J Am Mosq Control
Assoc 6: 689-693). In late 1991 one strain of M.
longisetus was obtained by the first two authors in Campinas,
State of S o Paulo, and maintained under laboratory cultures at
the Departament of Zoology/Universidade Estadual de Campinas
(UNICAMP). This strain (ML/01) was screened against Culex
quinquefasciatus and Ae. albopictus larvae and
appeared to be more effective against the latter species
(unpublished data). The aim of the present study was to evaluate
the predation capacity, survival and reproduction of M.
longisetus strain ML/01 in trap tyres, as a requisite
for its possible use as a control agent in the attract and kill
method.
Two field evaluations were performed. In the first one, ten
couples of trap tyres were distributed throughout an area of 245
ha in the UNICAMP campus. Each pair of traps was installed in a
shady place fixed to trees surrounded by vegetation. These sites
were shown to be successful in capturing Ae. albopictus
in previous monitoring programs. One tyre in each pair received
20 M. longisetus adults in 2.5 liters of tap water and
3% (v/v) of water from the mosquito breeding trays as food for
the microcrustaceans. The second tyre received the same treatment
except for the copepods and was considered as control. Predation
was evaluated during 10 days in 2 day intervals. In a second
trial 20 tyres were placed in pairs as before, but the traps with
copepods in this trial were 1/3 sections of the whole tyres, in
order to enable easier collection of the copepods at the end of
the experiment. Moreover, the volume of water was established
as 2 liters and the added food was increased to 20% (v/v). Slices
of polystyrene were placed floating on the water in order to
serve as resting and oviposition sites for adult mosquitoes. The
mosquito cohorts and copepod predation in this second trial were
evaluated during 32 days in 2 day intervals.
At each evaluation the water of traps without copepods was
transferred to pots and the mosquito larvae were collected for
counts and identification in the laboratory. The water in the
tyres with copepods was accessed in situ for the presence
of mosquito larvae. Only larvae in the two last instars were
removed for identification since predation occurs upon the two
first instars. Both evaluations received the same sampling
method.
At the end of both trials, the copepod-containing samples were
collected in order to access final amount of adult copepod,
amount of imature forms (copepodids) and reproductive females
with egg sacs. Mosquito cohorts naturally colonized the traps
along all the experiments with Ae. albopictus representing
99.2% of the traped larvae.
In the first trial the mean number of mosquito larvae found per
trap was 15.1 per 2 days for untreated traps and 0.4 per 2 days
for treated traps, resulting in a mean control efficiency of
97.5%. Copepod reproduction was shown to be low. In only 2 of the
10 traps reproductive females were observed (X=1.5), with
copepodids (n=2) occurring in only one of those traps. Copepod
survival ranged from 0 to 85% in the traps. In 4 of 10 tyres no
copepods could be recovered at the end of the trial but despite
this, mosquito larvae occurred in only one of those traps.
Although not accessed, we believe that copepod mortality occurred
at the end of the trial. It could be preliminarily concluded that
copepod survival and reprodution should be increased in such
traps.
In the second trial the number of mosquito larvae found in
untreated traps averaged 18.1 per 2 days while for treated traps
the average was 0.3 per 2 days, resulting in a final mean control
efficiency of 98.1%. Only two of 10 traps produced full grown
mosquito larvae during the trial, and only one trap produced
such larvae during all the trial span. This might be explained
considering that both these tyres contained only one copepod at
the end of the experiment. Due to the larger amount of initial
food, the mean copepod reproduction in this trial was found to
be greater than in the first one, represented by 8 of 10 traps
with reproductive females (X=15) and 6 of the 10 traps with
immature forms (X=58). Copepod mortality occurred in only 3 traps
ranging from 40 to 95%.
uThe attract and kill method has been widely used against many
agricultural pest in management programs and could be improved
against urban Aedes mosquitoes. Despite the relative
success of the evaluated M. longisetus strain against
Ae. albopictus larvae, a close monitoring of such traps
seems to be imperative to assure permanent control. The use of
this method of mosquito control in areas where trained employees
or community members could act as monitors is suggested.
Environments such as cemiteries, public parks, closed
condominiums and school campuses could be greatly benefited by
this attract and kill method of mosquito control.
^+Corresponding author. Fax: 55-19-239.3124
Received 11 July 1995
Accepted 31 October 1995
Copyright 1996 Fundacao Oswaldo Cruz
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