Journal of the American Mosquito Control Association, l3(1):87-89, 1997 Copyright @ 1997 by the American Mosquito Control Association, Inc.

USE OF BACTIMOS@BRIQUETS (B.T.J.FORMULATION) COMBINED WITH THE BACKSWIMMER IRRORATA ffiEMIPTERA: ) FOR CONTROL OF MOSQUITO LARVAE

J. F NERI-BARBOSA,I H. QUIROZ_MARTINEZ,I.' M. L. RODRIGUEZ.TOVAR,I L. O. TEJADA2 nNo M. H. BADII'

ABSTRACT The efficacies of Bacillus thuringiensis var. israelensis (Bactimoso briquets) and the backswim- mer Notonecta irrorata were evaluated both individually and in combination to control mosquito larvae in plastic containers in Monteney, Mexico. The combined strategy proved to be the most effective one.

The employment of effective mosquito control be used in combination with certain predator tactics is often the only means by which diseases speciesto effectively control mosquitoesin a cost- transmitted by these can be prevented or effective, environmentally safe manner. controlled (World Health Organization 1982). Over The objective of our study was to evaluate the the past half century, the primary tactics employed efficacy of using B.t.i. in combination with the against target mosquito populations have involved backswimmer Notonecta irrorata Uhler (Hemip- the use ofchemical larvicides and adulticides. Such tera: Notonectidae) to control mosquitoes. The 2 tactics, although effective when they are initially agents were assessedseparately and in combination employed, tend to eventually result in the devel- with each other on larval populationsof mosquitoes opment of resistance in the target mosquito popu- maintained under experimental field conditions. lations, severe suppression of nontarget organisms, The study was carried out at the fleld station of and/or general pollution of the environment when Instituto Tecnologico y de Estudios Superiores de these tactics are the only ones employed or other- Monterrey (ITESM) located near the Monterrey In- wise overused (Klowden et al. 1983). ternational Arrport, from September to December Thus, more biorational approaches are needed to 1994. Eight 20o-liter plastic containers were filled manage mosquito populations of public health im- with 150 liters of water and were exposed 15 days portance. One such approach would be to combine before treatment to natural oviposition by local a chemical insecticide that is highly specific for mosquito populations. The containers were situated mosquitoes and otherwise relatively harmless to the in a shaded place, surrounded by grass; the tem- environment with one or more biological control perature was 18-25"C and pH was 7.4-8.1. agents effective against these insects. A chemical The control agents used were Bactimoso slow- of the kind just mentioned is the toxin produced by releasebriquets (B.t.i., lOVoAI) and adult N. irror- the bacterium Bacillus thuringiensis var. israelensis ata, which were collected in artificial pools at the (B.t.i.\. ITESM field station. When B.r.i. was combined with mosquitofish A random square design with 4 treafinents was (Gambusia afinis), the combination of these 2 used. In 2 containers Bactimos was added at the agents gave better control of tarsalis Coq. equivalent rate of one briquet per 9.29 m2 per con- populations than when each agent was used sepa- tainer. We planned to reapply tllte B.t.i. when the rately (World Health Organization 1984), giving larval density reached5 larvae per dip. In the other evidence that B.t.i. can be used effectively in com- 2 containers the same concentration of Bactimos bination with at least noninsect predators of mos- was added plus 5 adult backswimmers per contain- quito larvae. er. The third set of 2 containers had only 5 adult However, B.t i. is highly toxic to certain other backswimmers added to each, and in the last set members of the Culicidae whose larvae are preda- nothing was added and these containers served as ceous on mosquito larvae, for example, Toxorhyn- the control. chites rutilus rutilus (Coq.) (Lacey and Dame Larval population densitieswere assessedweek- 1982). Fortunately, aquatic predators from other in- ly by taking 10 dipper samples from each treat- sect families are not affected by B.t.i. (Garcia et al. ment. The mosquito larvae were identified using 1980, Garcia and Sweeney 1986). This agent might the keys of Darsie and Ward (1981). The number of larvae collected for each mosquito specieswas I recorded. An analysis of variance was used to de- Laboratorio de Entomologia, Facultad de Ciencias tect treatment difference in larval densities (Zar Biologicas, U.A.N.L.; Apdo. Postal 105-E Ciudad Uni- r974). versitaria CP 66450, San Nicolas de los Garza, Nuevo Leon, Mexico. The mosquito speciescollected wete Aedes ae- 2 Programa de Graduados en Agricultura, ITESM, Cam- gypti (Linn.), Culex pipiens Linn., Culex cororufior "J", pus Monterrey, Sucursal de Correos CP 64849, Mon- Dyar and Knab, and Anophelespseudopunctipennis terrey, Nuevo Leon, Mexico. Theobald. The sampling data were analyzed ac- 88 JounNlL oF THE AMERIcAN Moseutro CoNrnor- AssocterloN VoL.

Table l. Pooled data reflecting average number of Table 2. Aedes aegypti larval densities in plastic mosquito Iarvae per dip per treatments for 4 mosquito containers treated with bactimos, backswimmers, and species occurring in containers treated with Bactimos, both agents at the ITESM Field Station, from September backswimmers, and with both agents at the ITESM through December 1994. Field Station, from September through December 1994. Average no. larvae per dip Average no. larvae per dip Days post- Back- Days post- Back- Inte- treatment Control Bactimos swimmer treatment Control Bactimos swimmer srated 7 o.7 0.1 0.0 0.2 7 0.8 3.4 3.9 t4 0.3 o.0 0.o 0.0 t4 2.7 0.6 0.5 0.0 2l 0.0 0.0 4.7 0.3 2l 7.3 0.3 4.9 0.3 28 0.8 o.0 0.3 0.1 28 2.5 0.0 1.6 0.1 35 o.4 0.0 1.5 0.0 Jf 2.2 o.4 l.8 0.o 4.O o.2 0.9 0.o A' tl.4 3.7 5.8 0.0 49 1.0 0.0 0.3 0.0 49 5.4 o.2 0.9 0.0 56 3.1 0.3 0.0 0.0 56 9.4 1.4 0.1 0.0 63 5.9 0.2 0.0 0.o 63 12.5 o.2 0.1 0.0 70 l3.l 0.0 2.r 0.0 70 15.6 t7.2 2.1 0.o

densities increased at the end of the evaluation. A cording to the following scheme: the data on 4 statistical difference between larval densities of Ae. mosquito species were pooled, and then Ae. aegypti aegypti was found among the treatments (P < was considered as a mosquito species by itself, and 0.05). data on Cx. pipiens and Cx. coronator were pooled In the case of Culex spp., the larval densities and considered as Culex spp. Data on An. pseudo- were greater than 5 larvae per dip by the end of the punctipennis were excluded because the larval den- evaluation in containers where Bactimos was ap- sities for this species were very low in all the treat- plied alone (Table 3). In the containers treated with ments. both agents the lethal effect on mosquito larvae was Using the pooled data on the 4 mosquito species, very obvious. In the case of the predator release the efficacy of Bactimos appeared to be very good alone the larval density reached 4.9 per dip at day (Table 1). By 42 days posttreatment, larval densi- 42 after treatment; in the case of the control, larval ties in the Bactimos treatment averaged only 3.7 densities were greater than 5 larvae per dip in 4 larvae per dip as compared to 11.4 larvae per dip samples. Statistically, a difference was found in the untreated control. T\e B.t.i. was applied among the treatments (P < 0.05). again only in this treatment because larval density Although we found efficient reduction of mos- was close to 5 larvae per dip and according to lab- quito larvae in both Bactimos application alone and oratory data, any residual effect was gone. In the the combined Bactimos and predator application, last sample (70 days posttreatment), the larval den- we recommend the second approach from an eco- sity was 17.2 larvae per dip. nomical point of view, that is, lower management The combination of both bacteria and predators costs, because the Bactimos had to be added less gave good control (low larval densities) with no frequently to containers having notonectids in them harmful effect on predators. The control afforded to effect the level of control desired. by N. irrorata alone was not as good as Bactimos alone although only in one occasion did the larval Table 3. Pooled larval densitiesof Culex spp. per density exceed more than 5 larvae dip. In the occurring in plastic containerstreated with Bactimos, control containers. densities of more than 5 larvae backswimmers,and both agentsat the ITESM Field per dip occurred during 6 sampling periods. The Station, from Septemberthrough December 1994. combination of both Bactimos and backswimmers larvae per dip consistently provided the best control of the pooled Average no. larval populations. There was a significant differ- Days post- Back- Inte- ence (P < 0.05) among the mosquito larvae den- treatment Control Bactimos swimmer grated sities when the different treatments were compared 7 3.5 0.7 3.4 3.4 to the control. t4 2.4 0.6 o.2 0.0 Aedes aegypti larval densities were similar in the 2l 7.3 0.3 o.2 0.0 Bactimos only and combined control agents, al- 28 1.7 0.0 1.3 0.0 ways less than one larva per dip (Table 2). Densi- 35 1.8 0.4 0.3 0.o ties of 0 larvae per dip again occurred more fre- 42 7.4 3.5 4.9 0.0 quently in the containers treated with both agents. 49 4.4 0.2 0.6 0.0 6.3 1.1 0.1 0.0 In the case of the predator strategy, Ae. aegypti lar- 56 63 6.6 0.O 0.1 0.o vae reach almost 5 larvae per dip in the 3rd sample 70 2.5 r7.2 0.0 0.0 (21 days posttreatment). tn the control the larval Mrncs 1997 OPERATIONAL AND SCIENTIFIC NOTES 89

This study was supported by Consejo Nacional Garcia. R., B. A. Frederici, I. M. Hall, M. S. Mulla and "Es- de Ciencia y Tecnologia through the project H. Schaefer. 1980. BTI-a potent new biological trategias de Manejo Integrado de Larvas de Mos- weapon. Calif. Agric. 34(3): 18-19. Klowden. M. J.. G. A. Held and L. A. Bulla. 1983. Tox- quitos" Ref. M9201/DO746.We thank Luis Lorens icity of Bacillus thuringiensis to adults of Aedes aegypti the of ITESM and for his assistance at Field Station mosquitoes. Appl. Environ. Microbiol. 46:312-315. Jonathan S. Cohen of Summit Chemical Co. for Lacey, L. A. and D. A. Dame. 1982. The effect of 8c- supplying the Bactimos briquets. J. K. Olson of cillus thuringiensis var. israelensis on Toxorhynchites Texas A&M University, and Noor S. Tietze of the rutilus rutilus (Diptera: Culicidae) in presence and ab- University of Florida also are thanked for revrew sence of prey. J. Med. Entomol. l9(5):593-596. and cofirments on this manuscript. World Health Organization. 1982. Manual on environ- mental and management for mosquito control with spe- cial emphasis on malaria vectors. WHO Offset Publi- REFERENCES CITED cations 66: I 8-27, Geneva, Switzerland. Darsie.R. E. Jr.and R. A. Ward. 1981. Identificationand World Health Organization. 1984. Report of the 7th geographical distribution of the mosquitoes of North Meeting of Scientific Working Group on Biological America,north of Mexico. Mosq. Syst.Suppl l:l-313. Control, Programme for Research and Training in Tiop- Garcia R. and A. W. Sweeney. 1986. The use of microbial ical Diseases. UNDP/lVorldBank. Geneva. Switzerland. pathogensfor the control of mosquitoes.Agric. Ecosyst. Za4 J. R. 1974. Biostatistical analysis. Prentice-Hall Inc., Environ. l5:2ol-228. Englewood Cliffs, NJ.

American Biophysics' ABC Trap y' Modular construction for easv Series is setting a new standardin parts replacement Dipteran collection equipment. y' lntegral dry ice container (trap Constructedfrom durable materials is also available with tubing for years of trouble free use, our connectionsfor CO2 tanks) traps have been designed from the y' bottom up to make your job easier: Polymer lid prevents battery shorting during transportation y' Exclusion ofmost non-dipterans y' Quick connect clip for hanging y' Net bag has small mesh, draw hap eliminates knot tying hassles string clips, write-on label, velcro aspiration port, and drop out tray Thesearejust a samplingofover 40 1/ User-friendly slow release features and innovations which octenol packets available (patent make our trap easier to use for pending) surveillanceor trap-out studies.For y' Extemal hanger for attractants more details call 4OI-423-3930 and y' Built-in photocell operation make your job easier today.

AME NICAN BIOPHY SICS CO NPO RATIO N 18 SouthwestAvenue, Jamestown, Rl 02835 (4O1)423-3930 Voice (401)423-391 O Fax