Laboratory and field evaluation of metallic copper on Aedes albopictus (Diptera: Culicidae) larval development.

Laboratory bioassays and field trials were carried out to study the effect of metallic copper on the development of Aedes albopictus (Skuse). Multiwire electric cable was used as a source of metallic copper. Three different doses were used in laboratory tests (5, 10, and 20 g/liter) and two in field tests (20 and 40 g/liter). In the laboratory, 10 g/liter induced high mortality and a lack of development in Ae. albopictus larvae and doses of 20 g/liter completely inhibited development. Larval mortality was higher in earlier instars than in third through fourth instars and pupae. No effects were reported on egg hatching. Copper ion concentration in water increased up to 574 ppb for 5 g/liter dose, 710 ppb for 10 g/liter dose, and 1,210 ppb for 20 g/liter dose, within week 6. The increasing concentration of copper in water was correlated positively with the decreasing production of adults. Copper ions concentration < 500 ppb did not or only slightly affected larval development and mortality of Ae. albopictus in laboratory tests. Copper concentrations between 500 and 1,000 ppb delayed larval development and caused high mortality. Copper concentrations > 1,000 ppb inhibited larval development completely killing all the larvae. This last result has been achieved by the use of a 20 g/liter dose of metallic copper in water. Copper also affected adult weight. In field trials, 20 g/liter reduced the number of larvae in treated pots by 90%, and 40 g/liter completely prevented oviposition. Moreover, the persistence of the toxic action of metallic copper in the field lasted for several months.