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1 E.I.D. - Nuisance mosquito control in natural mediterranean areas: methodological proposal for the sustained management of a Ramsar site in Languedoc-Roussillon LIFE99 ENV/F/ Project description Environmental issues Beneficiaries Administrative data Read more Contact details: Project Manager: Christophe LAGNEAU Tel: +33(0) Fax: +33(0) clagneau@eid-med.org Project description: Background Because of their biological landscape and socio-economic importance, particularly with regard to tourism, wetlands and coastal areas form a heritage zone for which preservation is a priority. However, these protected or labelled wetland or coastal areas are very favourable sites for the proliferation of numerous insect species which are vectors of viral or parasitic diseases (human and animal arboviroses - malaria canine filarioses, etc.) or which may be nuisant. These insects, mainly the mosquitoes, affect the quality of life of the local population and can represent a health risk. Mosquito control in 5 departments of Languedoc-Roussillon and Provence (the departments of Pyrénées-Orientales, Aude, Hérault, Gard and Bouches-du-Rhône) is a task which has been undertaken by EID Méditerranée for the last forty years. It consists of reducing to a tolerable level the nuisance caused by mosquitoes proliferating in the wetlands bordering coastal lakes and lagoons. The context in which mosquito control takes place has changed. More than ever, two elements are leading to changes in the means and methods which have been used up until now: - The growing awareness of the biological value of wetland areas is being seen in the adoption of labels and a protected status for them. This is in turn increasingly involving those responsible for managing the environment in the decision-making - The revision at European level of the approval for all pesticides intended for agricultural (agrochemicals) and domestic (biocides) uses, under two directives (dir. 91/414/CE and 98/8/CE, respectively). This situation means that the methods used by the European mosquito control operators will

2 have to evolve. Up to now the strategy consisted essentially in chemical control of larval breeding sites with organophosphorus insecticides, i.e. temephos, duly registered in France. Objectives This project proposed to demonstrate over a period of three years a methodology on a "real life" scale that makes control of the nuisance due to mosquitoes compatible with preservation of the environment. The methodology proposed was based on using a particularly selective insecticide of biological origin, Bacillus thuringiensis ser. israelensis (or Bti, an entomopathogenic bacterium), which would be assessed in parallel to the synthetic organophosphorous insecticide, temephos. The aim was to demonstrate to the local authorities the effectiveness of Bti and its low environmental impact, albeit with a higher cost (product and application prices), in comparison with temephos. The demonstration implied the following phases: 1. Complete the computerised ecological mapping of all the active breeding sites using standardised methodologies; 2. Organise a qualitative and quantitative standardised monitoring network for the evaluation of mosquito populations in order to measure and manage the effect on nuisance, 3. Organise a standardised data bank with ecological and meteorological parameters influencing mosquito breeding that might be used as a tool to carry on regular control and comparison phenomena; 4. Evaluate in the more representative breeding sites the qualitative and quantitative effects on aquatic invertebrates and phytoplancton, according to an original methodology finalised by the Laboratoire d'ecologie des Eaux Continentales Méditerranéennes (Université Aix-Marseille III); 5. Apply where necessary Bacillus thuringiensis var. israelensis on chosen areas using aerial or terrestrial spraying materials and methods. On the remaining areas, the organophosphorus insecticide, temephos, was to be used; Make a comparison of the biological effectiveness of the treatments (standardised bioassays of the World Health Organisation) and spraying characteristics. Results The "Petite Camargue" in the Gard department, a vast area of wetlands included in the Ramsar inventory as n.17, has been chosen to carry out this demonstration. It has been chosen for good reason, because the zone is an integral part of the EID Méditerranée action area and moreover forms in many respects a replica of the Grande Camargue which indeed has no mosquito control. 1. Mapping the habitats: The study carried out in the Petite Camargue has confirmed the usefulness of mapping wetlands where mosquitoes are controlled in order to locate larval breeding sites and monitor the effectiveness of their control. The ecological maps produced at 1/5000 remain well suited to this purpose. It is therefore planned to continue to update them. As regards mapping of habitats at a scale of 1/25000, studies based on vegetation surveys over the coastal area are envisaged in order to confirm their typology and continue to completely cover the EID Méditerranée area of action. 2. Assessment of the nuisance The in depth comparison of both methods (capture on human bait & carbon dioxide trap) on a common site should allow a nuisance threshold

3 to be estimated using only CO2 trapping. In fact, it seems that where human bait trapping captures 5 anthropophilic mosquitoes (nuisance threshold reached), a CO2 trap captures a minimum of forty. However, to date no linear relationship between both techniques has been demonstrated and this estimation should be statistically confirmed using a greater number of data entries. The CO2 trap has several advantages over trapping on human bait as currently carried out. In the first place it makes it possible to read fully both peaks of mosquito aggressiveness (evening and morning). Moreover, the capture of rare species not represented in the human bait captures can be interpreted as a view of the quality and/or limits of action in certain areas. Finally, with this method entomological monitoring of vector risks within the action zone is possible. Setting up a CO2 trap network has a relatively high cost both in terms of material (traps, batteries, dry ice etc) and logistics (delivery of dry ice, setting up/dismantling). Validation of the CO2 method of trapping requires working out and applying a study protocol to compare the two methods of trapping very carefully. This study will at the same time make it possible to define by reasoned choice the threshold for declaring mosquitoes of rural origin a nuisance in or at the edge of an urban zone. 3. Ecological Databank Lot of measures of soil and water have been carried out and the meteorological data have been collected but the beneficiary couldn t' create a real management tool of nuisance. However the EID operational agents make every day observations on site of the level of water. The water height is an indication of the mosquito larvae development. The collected data are connected to GIS and they are use as a signal to monitor the operational treatments. But this database exists before the project. 4. Evaluation the qualitative and quantitative effects on aquatic invertebrates and phytoplankton At present the efficiency assessment of a treatment is qualitative. In order to develop a more quantitative standardised evaluation method for effectiveness, a tool for estimating the abundance of larvae (abacus) has been created. It avoids manual counting of sampled larvae and makes it possible to take a large number of samples in a relatively short period (1:30-2 hours for 120 samples). Its use can be combined with spatial analytical techniques. The test site was prepared for treatment: it was divided into three strips (50 x 200 m) having the same ecological zones. The most westerly strip was treated with temephos (Abate 500 E), the most easterly strip with Bti (VectoBac 12AS), the central strip served as a control. In each of these three strips, 5 sampling points were selected and marked with a piezometric tube, each in a different ecological zone. Sampling of fauna was carried out before and after treatment at 5 previously marked sampling points in each strip. The insecticide concentrations were deliberately modified relative to operational doses, in order to determine the impact threshold. The numbers of taxa collected during these 5 periods of study were recalculated relative to the volume of water estimated using a digital model of the terrain, in order to analyse the density of individuals. It appears that when the concentrations are equal to or greater than the recommended doses (125 g of active substance/ha), temephos has a significant but short-term impact on Ochlerotatus spp., Gammaridae, Chironomidae, Anopheles and Calopterygidae. On the other hand, when the concentrations were lower than the recommended doses (68.3 and 70 g/ha in May and July 2002), temephos shows no marked toxicity including for Ochlerotatus spp. For concentrations generally greater than the recommended doses (0.8 l/ha), Bti has a significant impact on the larvae of Culex sp. And Anopheles sp., but on the other hand, the Chironomidae and other taxa are not affected. In order to refine the results and provide details on the persistence of the insecticides, the residues of Bti (in cooperation with the

4 Entomopathogenic bacterial and fungi laboratory of the Institut Pasteur in Paris) and temephos were analysed. The results indicated no or little Bti spore persistence in the 4 ecological zones after 2 treatments and that the strains of Bt, in particular Bti were rare in this temporary ecosystem. But these results were obtained after only a single season and it will be interesting to monitor potential persistence over several years. Concerning temephos, the results of the analysis of residues showed that there had not been an accumulation of the insecticide, neither in the ground, nor in ground water, during the period considered (Jan to Nov. 2002). The action of Bti was therefore more specific than that of temephos and the persistence of action of these 2 products, of short duration, does not cause noticeable modification in the populations studied at least in the medium term (equivalent to the years of monitoring). The qualitative and quantitative study of taxa, generally not very numerous during treatment, and of their numbers, throughout 5 treatment campaigns, shows no significant loss of biodiversity or biomass. In addition, it is clear that drying out has a greater disturbance effect than the use of the insecticides. These habitats have a large capacity for natural recovery. 5. Operational treatment and comparison of biological effectiveness of the treatments The proportion of Bti sprayed compared with synthetic larvicides has grown from a few % in 1999 to more than 20 % in The results have been satisfactory within the framework established but extension of its use on an operational scale to the whole of the area of action still remains limited by: * the irregularity of results which do not allow its routine use to be envisaged for larval biotopes situated near urban areas, * the volume of mixture to be sprayed per hectare, which seriously complicates spraying when action is required more than 30 or 40 km away from the refilling site. For extending this project it is therefore essential to: * develop new directions for research concerning new formulations approved at the end of 2002, such as VectoBac WG, with the prospect of low volume treatments; * test, over a complete season, the exclusive use of Bti in a sector of 150 to 200 ha, little exposed to external infestation and which up until now has been controlled using a synthetic product and is close to an urban area. A trapping system, which is as dense as possible should allow the results to be evaluated both on the treatment sites and within the built-up areas. The possible perception of the change of larvicide could be recorded from a survey among the population. Environmental issues addressed: Themes Land-use & Planning - Sensitive and protected areas management Keywords monitoring pest control research project coastal area wetland comparison

5 Target EU Legislation Nature protection and Biodiversity COM(95) "Communication on the judicious use and conservation of wetlands" ( ) Chemicals & Hazardous substances Development of new legislation Natura 2000 sites Not applicable Beneficiaries: Coordinator Type of organisation Description Entente Interdépartementale pour la Démoustication du Littoral Méditerranéen Development agency The beneficiary is the Entente InterDépartementale Méditerranée - EIM -, a public organisation which is responsible for mosquito control on the French Mediterranean coast since Administrative data: Project reference LIFE99 ENV/F/ Duration 15-NOV-1999 to 31-MAR Total budget 912, EU contribution 452, Project location Languedoc-Roussillon(France) Read more: Brochure Project web site Title: Actes du colloque Author: EID Méditérranée Year: 2003 Editor: EID Méditérranée web site

6 Publication: Layman report Title: Control of nuisant mosquitoes in Mediterranean areas. A methodological proposal for the sustainable management of a "RAMSAR" site in Languedoc-Roussillon (France) Author: EID Méditerranée Year: 2003 Project description Environmental issues Beneficiaries Administrative data Read more