Mature apple trees were sprayed using a Knapsack mistblower fitted
with 3 different nozzle systems, one of which provided an induced
electrostatic charge on the spray droplets.
Spray distribution was assessed by examining fluorescent tracer
deposits on Kromekote cards which had been positioned in different
parts of the tree canopy. Subsequently, bioassays with codling moth
(neonate larvae) and formulations of cypermethrin examined the biological effect of deposits.
Small uncharged droplets (30-60um VMD) sprayed at low volume
(3.0 4.8 ml/tree) with spinning disc gave the least deposit but
with an electrostatic charge, deposition was significantly improved
on the outer canopy. Intermediate results were achieved when sprays
were applied from an air-shear nozzle at 274.0 ml/tree. Directing
spray from both sides of the tree improved spray distribution with
all three nozzles.
Leaf Area Index (LAI) of the apple varieties used in the experiments was estimated in relation to tree height, and was used to calculate
the volumes of spray needed to improve coverage of the canopy.
Attempts to improve penetration into canopy were made by varying
the charge/mass ratio on the droplets, but a decrease in this ratio
reduced deposition (ng/cm2) within canopy.
Mortality of Codling moth was related directly to the level of
deposits, so there was a decline through the canopy. When large
droplets (140-152um VMD) were applied, about 300 droplets/cm2 were needed to deposit 2.75 ng/cm2 active ingredients (ai) to achieve at least 50
percent mortality or more. When smaller droplets (30-60um VMD) were
used the number increased to 900 droplets/cm2 to give similar deposits
of 4.0 ng/cm2 a.i. and achieve similar responses.
Cypermethrin formulations sprayed with each nozzle on apple
seedlings (variety Yarlington mill) were more persistent after
artificial rain (65.3mm for 15 mins.) when small droplets (VMD -
30.70um) were applied by spinning disc, compared with larger droplets
(VMD = 90-169um) produced by the air-shear nozzle. The under surface
of leaves were more protected from the direct action of impinging rain
droplets, and thus had greater mortality after rain. No significant
difference was obtained between droplets by either charged or uncharged spray (P = 0.05).
Eastern Network, L (2021). Spray Distribution In A Tree Crop. Afribary.com: Retrieved April 11, 2021, from https://afribary.com/works/spray-distribution-in-a-tree-crop
Library, Eastern Network. "Spray Distribution In A Tree Crop" Afribary.com. Afribary.com, 07 Apr. 2021, https://afribary.com/works/spray-distribution-in-a-tree-crop . Accessed 11 Apr. 2021.
Library, Eastern Network. "Spray Distribution In A Tree Crop". Afribary.com, Afribary.com, 07 Apr. 2021. Web. 11 Apr. 2021. < https://afribary.com/works/spray-distribution-in-a-tree-crop >.
Library, Eastern Network. "Spray Distribution In A Tree Crop" Afribary.com (2021). Accessed April 11, 2021. https://afribary.com/works/spray-distribution-in-a-tree-crop