Duration of activity of the microbial larvicide VectoLex CG (R) (Bacillus sphaericus) in Illinois catch basins and waste tires

The duration of activity of a formulation of Bacillus sphaericus, VectoLex CG(R), for control of Culex species was evaluated in 338 catch basins in Ur bana, IL, and compared to Altosid(R) in 346 catch basins in Champaign, IL. The activity of VectoLex in car and truck waste tires was evaluated in a ti re dump located in Pembroke Township, IL. In catch basins, 1 g of VectoLex per catch basin gave the same control as one Altosid briquet. Both larvicid es were effective against Culex sp. in catch basins for I month, and the du ration of control with VectoLex lasted 44 days in one catch basin. VectoLex was considerably cheaper to apply than Altosid briquets, at 0.64 cents per catch basin compared to 90.75 cents, respectively. However, the Altosid br iquets were judged to be easier to apply from a vehicle than VectoLex granu les. VectoLex (22.6 kg) was used to treat approximately 6,000 car and truck tires; some of the tires were in direct sunlight whereas others were shade d. Aedes triseriatus was the dominant species in these tires. Tires treated with VectoLex contained significantly fewer mosquitoes than control tires, and even 65 days after application, control tires were 16.7 times more lik ely to contain larvae. We conclude that VectoLex was effective when used in Illinois catch basins and tire dumps, and emphasize that it is more approp riate to base tire treatment rates on the total number of tires present tha n on a kilogram per hectare basis.