Characteristics of grass infusions as oviposition attractants to Aedes (Stegomyia) (Diptera: Culicidae).

Ovitraps baited with grass infusions were evaluated in the field as oviposition attractants or stimulants for Aedes (Stegomyia) mosquitoes. Significantly higher oviposition by Aedes aegypti (L.) was observed in areas with no vegetation, but intense human presence, whereas Aedes albopictus (Skuse) oviposition was significantly higher in areas with vegetation, regardless of human presence. Ovitraps baited with infusions of Panicum maximum (Jacq.) collected significantly more eggs than controls containing tap water. Moreover, the number of eggs deposited in ovitraps baited with infusion made from fresh, mature leaves was higher compared with dried leaves or fresh, immature leaves. Anaerobically fermented of grass infusions were more attractive than either aerobically fermented or sterilized infusions of P. maximum. The fermentation age of the grass infusion also affected the oviposition response of mosquitoes. Significantly more eggs were deposited in baited ovitraps containing a fresh leaf infusion of P. maximum fermented for 15 or 20 d, compared with the controls. This demonstrates that 15- or 20-d anaerobic fermentation made of fresh, fully mature leaves of P. maximum is the optimum infusion for ovitrap-based Aedes (Stegomyia) surveillance mosquitoes in Brazil. Neglecting to consider these differences in infusion attractiveness may introduce significant variation in surveillance results.