Assessment of canopy and ground deposits of fenitrothion following aerial and ground application in a northern ontario forest

Abstract

AbstractSpray deposit patterns on simulated and live foliage of balsam fir and white birch were determined at different heights and at periphery and interior locations of the tree crown, following aerial and ground applications of fenitrothion formulations over a boreal forest near Searchmont, Ontario. Droplet size spectra and AI deposits were assessed at ground level with ‘Kromekote’ card/glass plate units. Aerial application was made with a Cessna 188 aircraft fitted with ‘Micronair’ AU3000 atomizers. For ground application, a ‘Soloport’ 423 backpack mistblower fitted with an extension tube and a diffuser nozzle at the tip was used.Deposit data on the ground samplers indicated significantly larger droplets and greater deposits from the aerial spray trial than from the mistblower treatment. However, foliar deposits at tree canopy level were only slightly higher in the former trial than in the latter.Analysis of spray deposits on simulated and live fir foliage showed definite gradients in deposit levels, decreasing from top to bottom crown, and from periphery to inner tree crown. In the birch tree crown, such gradients were not observed. The simulated leaves generally acted as better collectors of spray droplets than the natural leaves. The overall mean deposit values, expressed in ng cm−2, showed a wide variation, although there was generally a close relationship between the deposits on the simulated and natural surfaces.