Wind-tunnel studies on the collection of airborne spray droplets by flying locusts

Abstract

In view of the present environmental awareness, the reduction of spray wastage, which in turn lessens environmental contamination, can be achieved by reducing spray volumes and improvement on spray efficiency through the use of correct ranges of spray droplet sizes. Published data on droplets collected by some insects consistently suggest that the optimum droplet sizes lie below 60 µm. An experiment was conducted in a wind-tunnel to assess the locust collection efficiency when subjected to a spectrum of droplet size ranges with a view to determine the optimum droplet size. Locusts were induced to fly in a wind-tunnel and then exposed to spray droplets which were produced by a spinning disc atomiser. Droplets collected on antennae, head, abdomen, legs and wings were sized and counted. The collection efficiency at wind-speeds ranging from 2 m/sec to 6 m/sec was calculated for the different body parts in the droplet size range 10–40, 40–60 and 60–80 µm. The calculated collection efficiency for the 10–40 µm size range was comparatively higher for all locust body parts.