EVALUATION OF THE FRANCOME MKII EXHAUST NOZZLE SPRAYER TO APPLY OIL-BASED FORMULATIONS OF METARHIZIUM-FLAVOVIRIDE FOR LOCUST CONTROL

Conidia of the fungus Metarhizium flavoviride were formulated in a par affinic oil, 'Shellsol' T, and sprayed using the Francome MkII exhaust nozzle sprayer. Germination of the conidia collected from the spray w as reduced by 30% as compared to unsprayed conidia. However, in bioass ays, there was no detectable difference in virulence with conidia coll ected from the spray samples and unsprayed formulation. This indicated that, despite the recorded reduction in the concentration of active c onidia, the efficacy of the formulation remained unchanged after passi ng through the exhaust nozzle sprayer. The droplet size spectra produc ed by the sprayer were investigated using the Malvern series 2600cc pa rticle size analyser. The optimum droplets for locust control produced by this sprayer were generated by the number 1 nozzle (internal diame ter 2.5 mm) with the number 1 restrictor ring (internal diameter 17.5 mm) sprayed at a pressure of 0.2 bar. The droplets thus produced had a volume median diameter of 58 mu m when the nozzle protruded between 1 and 2 mm above the level of the restrictor ring. Of the droplets in t he spray plume created by these conditions, 33% were between 50 and 10 0 mu m, a range recommended as an achievable optimum for the ultra-low -volume application of Metarhizium flavoviride. The role of the exhaus t nozzle sprayer as a tool for the application of M. flavoviride for l ocust control is discussed with reference to other vehicle-mounted ult ra-low-volume sprayers.