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

Abstract

Spray 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.

Deposition, distribution, persistence and fate of bacillus thuringiensis variety kurstaki (BTK) in pecan orchards following aerial and ground appucations to control pecan nut casebearer larvae

“…Such large differences could be due to differences in various operational parameters encountered during the spray applications [e.g., possible swath offset and overlap, canopy Downloaded by [The University of British Columbia] at 17:18 26 November 2014 height (13.6 m vs 10.8 m), wind speed and direction (4.2 km/h, W vs 5.8 km/h, WSW), RH (32% vs 25%), ambient temperature (18.6°C vs 21.5°C), volume rate (9.4 L/ha vs47 L/ha), atomizer type (Micronair vs disccore), blade angle orientation (35° vs 90° down), aircraft speed, and micrometeorological conditions (including turbulence at the canopy level, which increases the kinetic energy of droplets affecting target impaction) (Matthews, 1984)]. These results generally appear to support the findings of Himel et al (1987), Sundaram et al (1989a) and Teske and Barry (1993).…”

“…The D max values found on the horizontal disc samplers in Plot 1 were generally high at all three canopy levels (76 to 102 urn) due to gravitational sedimentation of droplets, compared to the values found on the vertical cylindrical samplers (51 to 58 urn) ( (Roltsch et al, 1994;MacNichol, 1995) and other conventional insecticides (Carman and Jeppson, 1974;Yates et al, 1974;Spillman and Joyce, 1978;Armstrong and Yule, 1978;1989a;Barry, 1984;Sundaram, 1987). The gradation observed was due to the canopy levels (NMD, 10.7 ± 1.8 to 12.6 ± 2.7 urn; VMD, 32.8 ± 3.0 to 35.3 ± 3.0 urn) were similar to the corresponding values obtained for the discs (NMD, 10.6 ± 1.9 to 11.7 ± 2.4 urn; VMD, 31.9 ± 2.7 to 43.1 ± 3.2 urn) [ANOVA P > 0.05 (Ryan et al, 1985)].…”

“…The droplet densities observed on the horizontal disc samplers at all canopy levels were considerably higher (19.8 ± 6.4 to 38.6 ± 10.9 droplets/cm 2 ) Downloaded by [The University of British Columbia] at 17:18 26 November 2014 than on the cylindrical samplers (1.7 ± 0.9 to 7.3 ± 3.3 droplets/cm 2 ) because the cylinders collected predominantly the upper end of the droplet size spectrum emitted (Sundaram et al, 1989a). The higher volume rate (47 L7ha) and hydraulic nozzle system used during the spray contributed to the higher droplet density, and larger D max and size spectrum observed in Plot 3 compared to Plot 1.…”

“…The reason for this trend, as discussed earlier, could lie in the geometrical shape of the collectors. Pecan leaves are flat and two-dimensional; therefore, they are able to collect the droplets emitted at the upper end of the droplet-size spectrum, compared to the narrow, somewhat cylindrical nutlets and budlets (Figure 3), which tended to collect (and probably retain) predominantly smaller droplets (Sundaram et al, 1989a). In addition, surface characteristics of the matrices and prevailing micro-meteorological conditions at the canopy site during the time of droplet impaction could have influenced the deposition patterns.…”

Role of physical factors on pesticide performance in forestry: An overview

“…If the layer could be made uniform and had a density of 1.0 g/cc, its thickness would be 0.05 //m [which is about 1/20 of the thickness of a spider web (Liu and Megaw, 1985)], and could not even be seen under an ordinary microscope. Furthermore, spray droplets seldom deposit uniformly on the entire foliar surfaces in the tree canopy (Armstrong and Yule, 1978;Sundaram, 1987) because droplets are usually filtered by the periphery of the canopy which is more exposed to the spray cloud than the interior parts. This leads to markedly higher deposits (up to ca.…”