Fig. 1.

Gravid Anopheles arabiensis respond to sugarcane pollen-associated odours. Schematics of the two-port olfactometer (a) and oviposition (b) assays. Attraction (c, e) and oviposition (d, f) preference of mosquitoes to the pollen headspace volatiles of the Coll 48 (light orange) and EAK 71-402 (green) sugarcane cultivars compared to the dichloromethane (DCM) control, respectively. Solvent only controls (DCM vs. DCM) are indicated (black) (a–d). An attraction or oviposition index of zero indicates a preference for neither treatment nor control. Attraction (g) and oviposition stimulation (h) of gravid An. arabiensis to the headspace volatile extracts of Coll 48 compared to that of EAK 71-402. i Electroanntenographic detection (EAD) traces depict voltage changes (mV) in response to the bioactive compounds in the pooled headspace extracts of both sugarcane cultivars, eluting from the gas chromatograph and registered by the flame ionisation detector (FID). Asterisks indicate responses to unidentified aromatic compounds (*) and other compounds present in the control headspace extracts (**). The identity and release rate of the bioactive compounds are shown at the left. A synthetic blend (blue; FB) composed of the eleven bioactive compounds identified, in their natural ratio (i), elicited attraction (j) and stimulated oviposition (k) in gravid mosquitoes in a dose-dependent manner when diluted in pentane (PEN). Ten replicates, of 10 mosquitoes each, were used in each behavioural experiment. Error bars represent standard errors of the mean