Evaluation of Alternative Methods for Testing the Bioefficacy of Household Ambient Insecticide Products Against Aedes albopictus.

Ambient insecticides are receiving increasing attention in many developed countries because of their value in reducing mosquito nuisance. As required by the European Union Biocidal Products Regulation 528/2012, these devices require appropriate testing of their efficacy, which is based on estimating the knockdown and mortality rates of free-flying (free) mosquitoes in a test room. However, evaluations using free mosquitoes present many complexities. The performances of 6 alternative methods with mosquitoes held in 2 different cage designs (steel wire and gauze/plastic) with and without an operating fan for air circulation were monitored in a test room through a closed-circuit television system and were compared with the currently recommended method using free mosquitoes. Results for caged mosquitoes without a fan showed a clearly delayed knockdown effect, whereas outcomes for caged mosquitoes with a fan recorded higher mortality at 24 h, compared to free mosquitoes. Among the 6 methods, cages made of gauze and plastic operating with fan wind speed at 2.5-2.8 m/sec was the only method without a significant difference in results for free mosquitoes, and therefore appears as the best alternative to assess knockdown by ambient insecticides accurately.

The presence of white eggs in the monitoring of Aedes albopictus ( Diptera: Culicidae) by ovitraps.

Using international trading and passive transportation routes, the Asian tiger mosquito, Aedes albopictus (Skuse, 1894), has colonized Europe. While the most common tool to monitor the presence of the mosquito is the ovitrap, other kinds of eggs are occasionally found in the traps as well. Most of the eggs are easy to distinguish, however, some white-yellow eggs have a similar shape and size to those of the tiger mosquito and are often falsely identified as freshly laid tiger mosquito eggs. We have shown that these eggs had been laid by Psychoda alternata Say, 1824, and the misinterpretation may cause large errors in calculating density and patterns of Ae. albopictus. To avoid mistakes, a microscopic observation should be done at least 48 h after collecting the sample to permit Ae. albopictus eggs to darken.