Insecticidal effect of registered larvicides against Culex pipiens (Diptera: Culicidae) under laboratory and field conditions

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1 Integrated surveillance and control programme for West Nile virus and malaria in Greece (MIS ) Insecticidal effect of registered larvicides against Culex pipiens (Diptera: Culicidae) under laoratory and field conditions Athanassiou C.G., Ioannou C., Sakka M. Laoratory of Entomology and Agricultural Zoology, Department of Agriculture, Crop Production and Rural Environment, University of Thessaly, Co-funding y European Union

2 Background Culex pipiens: Important WNV vector Increase of WNV cases in Greece during the last yearsnumerous deaths Insecticidal applications are proaly the most important action in managing mosquito populations From the availale insecticides, larvicides can e used as a tool for area-wide management Larvicides are essential where drainage is not availale or adequate Effective treatment against larvae requires the identification of larval sites: Larviciding means Surveillance!!

3 Floodwater pools

4 Questions raised- Aims of the present work Efficacy of all registered larvicides in Greece against C. pipiens Efficacy in comparison with temephos (withdrawal in 2007) and non-iocide formulations (Aquatain) Influence of aiotic and iotic factors on larvicide efficacy (exposure etc.), including residual effect Testing different strains (wild vs la mosquitoes) Testing larvicides under oth la and field conditions

5 STATUS in Greece UNTIL Temephos (OP) Bti (acterial) Difluenzuron only as WP) (IGR, Bti (2 formulations) Difluenzuron (7 form. SC, DT, GR) Spinosad (acterial, 1 form.) Pyriproxifen (IGR, not used) S- methoprene (IGR, 1 form.) Polydimethylsiloxane (PDMS, inert material, 1 form., not a iocide)

6 The six larvicides used in the tests Temephos (OP, neurotoxic) S- methoprene (IGR, juvenile hormone analogue, non-neurotoxic) Difluenzuron (IGR, chitin synthesis inhiitor, nonneurotoxic)

7 The six larvicides used in the tests (2) Spinosad (acterial metaolites, neurotoxic) PDMS (intert material, acts mechanically, NOT A BIOCIDE) Bti (acterial toxins, not neurotoxic)

8 Formumations that tested for each active ingredient Formulation Du-Dim 15 SC Vectoac 12 SC Biopren BM 20 Aquatain AMF Mozkill 120 SC Aate Active ingredient Difluenzuron Bacillus thuringiensis (H-14) S-Methoprene PDMS Spinosad Temephos

9 Test 1: La efficacy assessment The tests were carried out in walk-in chamers of controlled conditions (3 x 3 x 2.7 m, 24.5±0.5 ºC, 75±5% RH, photophase 14L:10D) Larvae from F3-F10 of la strain

10 The tests were conducted in plastic containers with 150 ml of water and 15 mg of food (daily) The larvicides were applied at the lael rate on the surface (approx. 47 cm 2 ) The containers were sealed and kept at the same conditions for 3 months Bioassays were performed at weekly intervals (20 3 rd instar larvae /container)- 6 reps

11 Efficacy was recorded according to the numer of emerged adults

12 Test 2: La evaluation of larvicides against a wild C. pipiens population Similar ioassays as in the case of Test 1 Larvicides used were Du-Dim, Orpah (difluenzuron), Mozkill, Biopren, Vectoac Two dose rates: lael rate and 1/3 of the lael rate, 14 days of exposure Separate ioassays at two larval instars, 3 rd and 4 th

13 Test 3: Efficacy assessment in field conditions Rearing and ioassays were conducted as in the previous test Containers were sealed and placed outside, at the eginning of the months May, June and July 2013 (separate containers for each month) Efficacy was recorded at weekly intervals, as in the previous tests

14 Test 4: Delayed effects on adults In cases of mortality <50 %, the adults emerged were transferred ack to walk-in chamers at plexi-glass oxes (20 x 20 x 20 cm) with food (10 % sugar) Adult survival was assessed 28 d after their emergence (lood-feeding was carried out on the 20 th day for 30 min) Other parameters tested: Oviposition Numer of females that oviposited Egg hatching/larval emergence

15 Mean mortality ± SE Results: la tests Treated Control (untreated) Biopren Du-Dim Vectoac Aquatain Aate Mozkill Days after treatment

16 Mean mortality ± SE Results: la tests with wild C. pipiens Α * * * * * Treated Control Β * * * * * * Vectoac Mozkill Biopren Oprah Du-Dim Efficacy of lavicides agaisnt 4 th (A) and 3 rd instars (B) at the lael rate

17 Mean mortality ± SE Results: la tests with wild C. pipiens (2) * * * * Treated Control Vectoac Mozkill Oprah Du-Dim Efficacy of lavicides agaisnt 3 rd instars at 1/3 of the lael rate (Biopren was not included since there was no mortality)

18 Mean mortality ± SE Results: Field tests MAY 2013 Full month exposure Control Aate Du-Dim Aquatain Days after treatment (from the eginning of May 2013) Vectoac, Mozkill and Biopren had no significant differences in comparison with the control containers No significant differences in the iological parameters of adults in comparison with control These three formulations were tested for 1,3,5 and 7 days of exposure in the first week of June

19 Mean mortality ± SE JUNE day exposure 100 a c c Control Vectoac Mozkill Biopren

20 Larval emergence % of females that laid eggs Adult survival (%) Biological parameters of the adults that emerged JUNE day exposure a a Control Vectoac a Biopren Males Females a

21 Mean temperature ( ºC) Mean mortality ± SE JUNE day exposure Control Mozkill Days

22 Mean mortality ± SE JUNE 2013 Full month exposure Control Aate Du-Dim Aquatain Days of exposure from the eginning of June 2013

23 Mean mortality ± SE JULY 2013 Full month exposure Control 50 Aate Du-Dim Aquatain Days of exposure from the eginning of July 2013

24 Larval emergence % of females that laid eggs Adult survival (%) Biological parameters of the adults that emerged a JUNE 2013 Full month exposure a a Control c Aate Du-Dim 100 a a

25 Mean mortality ± SE SUM of FIELD TESTS for MAY, JUNE, JULY Aate a MAY JUNE JULY a Du-Dim a a c Aquatain a a a Weeks after treatment

26 Summary of efficacy of larvicides More effective LAB TESTS Spinosad (Mozkill) PDMS (Aquatain) Temephos (Aate) Difluenzuron (Du-Dim) FIELD TESTS PDMS (Aquatain) Temephos (Aate) Difluenzuron (Du-Dim) Less effective Bt-i (Vectoac) S-Methoprene (Biopren) Spinosad (Mozkill) Bt-i (Vectoac) S-Methoprene (Biopren)

27 Conclusions Noticeale differences in the efficacy levels of the tested larvicides Spinosad: increased efficacy in the la, quick dissipation outside PDMS: increased efficacy in all tests PDMS, aate and difluenzuron more stale- etter residual effect Month had a critical influence on efficacy: efficacy is a function of conditions (temperature, sunlight etc.) Adult survival and iological parameters were only marginally affected Adults that had survived laid eggs Egg hatching/larval emergence was not affected

28 What s next Evaluation of more factors that affect larvidides (more species, more scenarios), incl. novel sustances Additional studies on PDMS efficacy Assessment of efficacy of larvicides in real-world conditions (i.e. sampling and ioassays right after field application etc.) Screening for resistance to larvicides (for Greece) THANK YOU!!