Attraction of Chironomus salinarius (Diptera: Chironomidae) to artificial light on an island in the saltwater lagoon of Venice, Italy.

The attraction of adult Chironomus salinarius to incandescent 3-W lamps of 7 different colors used in CDC traps was studied on a small island in the lagoon of Venice, Italy. An ANOVA indicated that the lamp type was a highly significant (P < 0.01) factor associated with differences in light trap catch (28% of total variation), as well as catch per lux (18% of total variation). The white lamp attracted higher numbers of adults than the other 6 color lamps. Yellow was the second most preferred, and red was the least attractive. There was a strong linear relationship (r = 0.93) between the catch and light intensity, which suggested that intensity was the primary factor influencing catch. However, catch per unit brightness (lux) tended to be inversely proportional to the peak wavelength associated with the lamp color (e.g., the violet lamp had the highest catch/lux, and the red lamp had the lowest). The corresponding regression model, Catch = 49 + [(48,013/lambda) - 63] . L, in which the slope associated with light intensity in lux (L) is inversely proportional to the peak wavelength in nm (lambda) explained 97% of the variation among lamp catch means. Manipulating light intensity and color could be useful to divert adult C. salinarius populations from midge-affected areas for control purposes.

Efficacy of two temephos formulations against Chironomus salinarius (Diptera: Chironomidae) in the saltwater lagoon of Venice, Italy.

Two formulations of the organophosphorus insecticide, temephos (Abathion Granulare, 1% AI granular and Tambro Compresse, 2% AI tablet) were evaluated against Chironomus salinarius midge larvae in 50 x 50 m experimental plots in the saltwater lagoon of Venice, Italy. Each formulation was applied at 0.2 and 0.4 kg AI/ha. Abathion Granulare produced 56 to 73% larval reduction at 0.2 kg AI/ha and 69 to 83% reduction at 0.4 kg AI/ha during 3 wk after treatment. Abathion Granulare lost effectiveness at 4 wk after application at both rates. Posttreatment larval reductions resulting from Tambro Compresse applications ranged from 77 to 86% for 3 wk, and 82 to 92% for 4 wk at rates of 0.2 and 0.4 kg AI/ha, respectively. The tablet formulation (Tambro Compresse) gave better control of C. salinarius (magnitude and duration) than the granular formulation (Abathion Granulare) in these evaluations.

A chironomid (Diptera: Chironomidae) midge population study and laboratory evaluation of larvicides against midges inhabiting the lagoon of Venice, Italy.

Chironomid larval densities in the saltwater lagoon of Venice, Italy, were assessed in the spring of 1984. Four organophosphates; chlorpyrifos, temephos, fenthion and fenitrothion, and three pyrethroids; cypermethrin, permethrin and deltamethrin, were tested in the laboratory against field-collected larvae. Three industrial formulations of Bacillus thuringiensis var. israelensis (B.t.i.) were also tested as midge larvicides. Only Chironomus salinarius occurred in the benthic samples taken from different sections of the lagoon. The densities of this species ranged from 0 to 38,976 larvae/m2. The highest mean larval density of 15,673/m2 was encountered in a section of the lagoon adjacent to Venice airport and receiving large quantities of raw sewage. The lowest mean density (less than 1 larva/m2) existed in another area of the lagoon receiving discharge from chemical industry. Cypermethrin and permethrin were 21-233X more active against the larvae than the four organophosphates. Chlorpyrifos was the most active organophosphate. Formulations of B.t.i. were economically ineffective against the larvae.