ISHS Acta Horticulturae 372: Symposium on Engineering as a Tool to reduce Pesticide Consumption and Operator Hazards in Horticulture
SPRAYING APPLICATION AND DEPOSIT OF PESTICIDES IN ORCHARDS |
| Author: | N. Bjugstad |
| Keywords: | deposit, equipment, volume rate, electrical charging, apple orchard |
| Abstract:
The deposit of pesticide was measured when using a Hardi Maxi SPV orchard mist blower with standard hoses and with long hoses, both with and without electrical charge (induction method, 5 kV). Experiments were carried out with and without air, at different volume rates, with different tree sizes and pre and post blossom. The climatic parameters were noted during the experiments. RbCl was used as a tracer. Rubidium is easily detected at low concentrations by atomic spectroscopy. Electrical charging of the droplets generally resulted in better spray deposit of between 6.6 and 46.5%. The copper induction electrodes used are inexpensive and simple. The nozzle position, shape of electrodes and air speed are important for adequat charging of the droplets and for preventing an electrical short circuit. The use of air assistance in trees post blossom increased the deposit in the center of the trees by 460%. A mist blower was altered to improve spray quality, however, the rebuilt model did not give the increased amount of pesticide deposit expected. Before blossoming it caused a reduction of 20.8% and after blossoming the deposit increased by 4.9% compared with the standard model. Better adjustment and outlet position would probably increase the deposit. The amount of pesticide in the center of large trees was 42% lower than for small trees. The deposit in the same tree position after the blossom was 45% lower than before the blossom. The volume rate has to be adapted to different tree size and mass of leaves. In Norway growers use a check list to adapt the necessary dose and volume rate according to tree size and mass of leaves, which gives the opportunity to reduce the dose from 100% to 40% without losing any biological effect. | |
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