Journal of the American Mosquito Control Association, 14(2):196-199,1998 Copyright O 1998 by the American Mosquito Control Association, Inc. BVA 2 MOSQUITO LARVICIDE-A NEW SURFACE OIL LARVICIDE FOR MOSQUTTO CONTROL T, G. FLOORE,' J. C. DUKES.T J. P. CUDA., E. T SCHREIBER' AND M. J. cREERt ABSTRACT. BVA 2 mosquito larvicide was evaluated in laboratory pan tests against 3rd-instar Aedes tae- niorhynchus (Wied.), Culex quinquefosciatus Say, and Culex nigripalpus Theobald larvae. BVA 2 was as effec- tive as the standard, GB-1111, at 14 liters/ha (>99.lVo vs.99.8Vo). In small field plot tests BVA 2 mosquito larvicide applied at 28 liters/ha was as effective as GB- 1 1 I I (99 .OVovs. 99 .87o) 24 h posttreatment. Operation- ally, applied by helicopter at 46.8 liters/ha, BVA 2 mosquito larvicide was more effective (>9OV") in the slightly less vegetated site than in the heavily vegetated site. As a pupicide applied at 14 liters/ha in laboratory pan tests, no significant differences were noted between BVA 2 mosquito larvicide and GB-llll against Ae. tae- niorhynchu,s, Cx. quinquefasciatus, and Cx. nigripalpus pupae. KEY WORDS Operational field laboratory, Diptera, Culicidae, Aedes taeniorhynchus, Culex, pupicide INTRODUCTION mulations were evaluated (unpublished data). Less than 2Vo differences in mortality The use of petroleum oils as mosquito larvicides separated the 3 formulations from in the United States dates to 1793 in Philadelphia one another and less than 57o separatedthem from the (Howard 1928). Early petroleum-based larvicides standard,GB-1111. B-V (Wixom, such as diesel oil, kerosene,or tar oils were odor- Associates MI) chose the BVA 2 formu- lation reported iferous and often discolored the water's surface for on here for further study based on the several days (Headlee 192I, Lowry 1929, Howard initial study. 1932, lI0'4,aJJ1933, King et al. t944). Current prod- ucts, although derivatives of petroleum distillates, MATERIALS AND METHODS are nearly odorless and clear (Anonymous 1990, Laboratory Floore et al. 1992). Phytotoxicity and other detri- studies: Laboratory bioassay tests mental effects some petroleum oils have on certain were conducted in 61 X 6l X 10-cm pans filled nontarget aquatic organismshave lead to the elim- with 16 liters of well water. The proceduresfor the laboratory and plot ination of all of these products except Golden small studieswere describedby Floore (1991). Bear@-1111(Golden Bear Oil Specialties,Oildale, et al. One hundred 3rd-instar mos- quito CA) (GB-1111) and Bonide@(Bonide Products, larvae were placed in each pan before treat- Inc., Yorkville, NY) (Gjullin 1968, Mulla et al. ment. [n the Ae. taeniorhynchrs tests, 60 g of re- 1969,Schmidt et ^1. 1973,Levy et al. 1980,Mulla agent grade NaCl (Fisher Scientific, Inc., Atlanta, and Darwazeh 1981).Currently, these2 surfaceoils GA) was added to the water prior to adding the (5Voa are labeled as larvicides/pupicides. Pupicidal ef- larvae salinity). The 14 liters/ha application (1.5 fects of larvicide oils had been documented by rate gallons per acre, GPA) was basedon 0.37 Howard (1917), Lowry (1929>, and Micks et al. m2 of water surface area.Five tests were conducted (1e68). againsteach speciesin the laboratory with eachtest For several years studies evaluating candidate consisting of 2 pans of BVA 2 mosquito larvicide surface oils as mosquito larvicides have been con- formulation, I pan of GB-llll, and L untreated ducted by the John A. Mulrennan, Sr. Arthropod control. Larvae were considered dead if they did Research Laboratory, Panama City, FL (JAM- not move when touched by a glass probe. Larvae SARL). This paper reports the results of a study treatedwith GB- I I 1I sank to the bottom of the pan comparing BVA 2 mosquito larvicide with GB- when dead. Larvae treated with BVA 2 mosquito 1111 against 3rd-instar Aedes taeniorhynchus larvicide floated on the surface when dead. Water + (Wied.), Culex quinquefasciatusSay, and Culex ni- temperature during the laboratory tests was 26 gripalpus Theobald larvae and pupae in laboratory 1"C. pupae and small plot field tests. Also, results of an oper- In the tests,4 testswere conductedagainst lN Ae. ational study conductedby the Hillsborough Coun- taeniorhynchus,Cx. quinquefosciatus,and pupae ty Mosquito and Aquatic Weed Control Department Cx. nigripalprr in laboratory pans. Mortality (HCMCD), Tampa, FL, is presented.In initial lab- was assessedby determining the emergenceinhi- (EI) (Floore oratory pan bioassaytests 3 candidateBVA oil for- bition et al. 1991): CS_DA VoEl: t* - x roo). IJohn A. Mulrennan, Sr. Artbropod Research Labora- (CS+PE+DP tory Florida A. & M. University, 40OO Frankford Avenue Panama City, FL 32405-1933. where CS is cast skin, DA is dead adults, PE is 2 Department of Entomology and Nematology, Univer- partially emerged adults, and DP is dead pupae. sity of Florida PO. Box 110620, Gainesville, FL 32611- Water temperature during the pupae laboratory tests -{- 0620. was 26 1'C. 196 Jur,rB1998 A Nr,w Sunracs On Lenvrcron t97 Laboratory small field plot studies: Small plot Table 1. Laboratory tests of BVA mosquito larvicide field study application rates (28 liters/ha, 3 GPA) compared to GB-1111 against 3rd-instar Aedes were based on 0.93 m2 of water surface area. These taeniorhynchus, C ulex quinquefasciatus, and Culex nigripalpus lanae 24 h posttreatment.r-l tests were conducted in a screened enclosure at the JAMSARL in concrete cattle watering tanks (J. B. BVA mosauito larvicide oil GB-l111 Hill Contractor, Inc., Leesburg, FL) that measured Formu- X 1.7-m long X 0.6-m wide 0.6-m deep. The Cx. lation 7a control + SE Ea colrfiol + SE quinquefascialus and Cx. nigripalpus bioassays were conducted in freshwater and tlre Ae. taenio- Aedes taeniorhynchus^ rhynchus bioassays were conducted in tanks filled 95.91' r.43 100.00, 0.00 with salt water pumped from a saltwater canal de- Culer quinquefasciatus^ scribed by Rathburn and Boike (1975). Pretreat- 97-92, t.t2 99.88" O.1l ment assessments and posttreatment mortality were Culex nigripalpus^ determined by dipping larvae using a standard mos- 99.33" 0.67 100.00, 0.00 quito larval dipper at 8 stations located at each cor- ner of the tank (4), the middle of each long wall 'Application rates: BVA oil and GB-1111 at 14 liter/ha (1.5 axis (2), and 2 areas along the center axis of each gallons per acre). 'Species followed by different uppercase letter represent signif- tank approximately 30.5 cm from each end. Water (P : -r icant differences 0.05) between species using least significant temperature during the tests was 29 3"C and the differences (LSD) multiple comprison test. salinity in the saltwater plots was +l8Voo at treat- 3 Means followed by different lowercase letter represent signifi- (P : ment. cant differences 0.05) between treatments usins LSD mul- tiple comparison test. Analysis: Larval mortality was assessed by counting the number of larvae in each pan or plot 24 h posttreatment. All the larvae were counted in Percentreduction was assessedas percentreduction the pans and in the plots only those actually dipped using the following formula (Mulla et al. 1971): were counted. Treatment means were separated by Toreduction analysis of variance (ANOVA) PROC GLM and : - least significant differences (LSD) multiple com- 100 [(no. larvae control pretreat- parison tests (SAS Institute l99O). Differences were ment X no. larvae treatment considered significant at P : 0.05. Pupicidal data were assessed and analyzed in a manner similar to postreatment) the larval data described above. + (no. larvae treatmentpretreat- Operational study: In the operational study, con- ducted at the Seaboard sewage effluent sprinkler ment X no. larvae control field in Hillsborough County, Florida, BVA 2 mos- postreatment)l X 100. quito larvicide was applied at 46.8 liter/ha (5 GPA) by a Bell 47 helicopter equipped with 20 disc core This formula assumedthat changes in the mosquito nozzles (TeeJet DIO/45, Spraying Systems Co., larval population were occruring at the same level Wheaton, IL) attached to a 9.8-m boom. Applica- and rate in both treated and untreatedcontrol sites. tion was from a height of 3.3 m at an airspeed of Comparisons within and among sample sites, and among sampling 74 kilometers/hr and a swath width of 21.3 m. The times to assesslarval abundance procedures treatments were initiated at O8O0 h. were made by ANOVA PROC GLM and LSD multiple comparison tests after arcsin Ditching characteristics of the 28.3-ha study sites transformation of the data (SAS Institute 1990). allowed for a portion of each cell (A, B, and C cells) to be utilized as either a treated or untreated control site. The initial test was conducted in April RESULTS AND DISCUSSION 1993 when the vegetation (various grasses and Laboratory: In the laboratory pan test no signif- woody shrubs) in the study site was 18-61 cm in icant mortality differences existed between species height. In October when the last test was conduct- (P : 0.2018) (Table 1). The treatments were sig- ed, the majority of the vegetation exceeded 1 m. niflcantly different from the control (P : O.OOO1). The mosquito species complement at the sprin- No differences were noted in the treatmentby spe- kler field was Aedes sollicitans (Walker), Anopheles cies interaction (P : 0.1054), or between larvicide crucians Wied, Anopheles quadrimaculatus Say, oils (P : O.O272). Cx. nigripalpus, Cx. quinquefasciatus, Psorophora In the laboratory bioassay test the BVA 2 mos- ciliata (Fabricus), and Psorophora columbiae quito larvicide was as effective as the GB- I 1I 1 for- (Dyar & Knab) throughout the season. mulation in controlling Ae. taeniorhynchus(95.97o Operational data analysis.' Twenty larval sam- vs.