Assessing larvicidal ground-based applications on Aedes albopictus by misting BTI
Roger Eritja
Servei de Control de Mosquits,Consell Comarcal del Baix Llobregat, Parc Torreblanca s/n, 08980Sant Feliu de Llobregat, Spain
Mosquito control in urban environment is a complex topic. Adulticiding applications are restricted by legal issues and larviciding applications using Bacillus thuringiensis israelensis are not cost effective for container-breeding species, because larvae are scattered in many small breeding places in private ground that
cannot be individually sprayed.
The presence of Aedes albopictus in Spain since 2004 has challenged the urban mosquito control in the Baix Llobregat region, performed since 1983 by the Mosquito Control Service of the Baix Llobregat Regional Council in 19 municipalities totalling a population of 879,000 over a surface of 250 sq km. Operations
include larviciding and adulticiding in public areas, education at primary schools, raising concern by spreading information, and promoting suppression of breeding places.
There are strong evidences that the majority of the breeding sites are found in private areas. However, larviciding operators either cannot legally enter the area where the breeding containers are found, or there are too many containers to individually apply Bti by hand. Though such situations can only be managed by
chemical adulticiding, they would be obvious candidates for distance larviciding by misting or cold fogging, provided the availability of suitable Bti formulations.
In cooperation with the manufacturer Valent Biosciences Inc. it was decided to set a test on the performance of misting their Vectobac WDG formulation via a low-volume misting Martignani 748 machine, at a dose of 1 kg of powder per hectare, using adequate dilution rates to accommodate outputs of 200 to 500 liter per
hour.
An array of five single-floor holiday cabins were used to simulate urban conditions in an abandoned camping ground. Small plastic containers ca. 250 ml each were placed in several locations of the housings up to 31 meter from the application path. All tests were duplicated and controls were used. After spraying, they were
brought to the laboratory and populated with Aedes albopictus larvae to assess the mortality rates at 24 and 48 h.
The tested output rates behave slightly differently but a mortality near to 100% could be obtained up to a distance of 20 meter. These promising results will be discussed along to the environmental factors to be considered, as well as further test planning.