ITHACA, N.Y. - Maximum economic return will be obtained with a finely tuned sprayer, as it provides better disease control and is more cost-effective.
There are three factors that affect application rate:
- Forward speed;
- Nozzle size; and
- Systems pressure.
Forward speed affects both dose rate and volume rate - double the speed, and you halve both. Remember to drive at a speed that provides a stable boom. Moving too fast results in boom bounce, leading to incorrect nozzle height above the target. Moving too slow results in not applying pesticides in a timely manner, failing to cover the ground and keeping on top of pest outbreaks.
| The Interrelationship Between The Factors Affecting Application Rate | ||||||||||||||||
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NOZZLE SELECTION. Nozzle selection is so important. Droplets are measured in microns - 100 microns is about the thickness of a human hair. Remember large drops bounce, and such droplets are more than 300 microns and are created by using low pressures, too large a nozzle orifice and or worn nozzles. Too fine a droplet (less than 150 microns) will drift, resulting in damage to neighboring properties, nuisance complaints and, equally important, reduced application to the target.
Select the correct nozzle for the target. Use a nozzle that creates a fine spray for fungicides and insecticides. A medium quality spray is ideal for herbicides. Coarse spray is ideal for applying liquid fertilizers and preemergent herbicides to bare soil.
NOZZLE WEAR. The rate of nozzle wear will depend upon the pressure used, type of pesticide being used and nozzle material. Note that ceramic nozzle tips, whilst being expensive, do last much longer than cheap plastic nozzles. Nozzles made from modern polymers are also superior to cheap plastics. Brass is the worst nozzle tip to use, as it wears out so rapidly.
NOZZLE ABUSE. Nozzle abuse is a problem caused by operators using a piece of wire to clean out a blocked tip. Rodding out a ceramic tip with a piece of wire is the kiss of death - it will damage it, thus affecting flow rate and spray pattern. Remember, good filtration and agitation will prevent nozzle blockage. If a nozzle does block, replace it with a spare and blow out the blockage with an airline or use a bristle brush - never kiss nozzles.
SYSTEM PRESSURE. System pressure affects flow rate, nozzle life, droplet size, fan shape and penetration into the target. Too low a pressure will result in large droplets dripping off the target. Too high a pressure results in off-target drift and poor application. Beware that some automatic electronic controllers will alter flow rate by using a butterfly valve to change system pressure. Always work within the boundaries recommended in the sprayer manual.
Good preseason maintenance and calibration is so important. The author on this subject has published articles that are available at http://aben.cals.cornell.edu/extension/pestapp/boom.html.
Remember, good pesticide application is a wonderful blend of technology and common sense.
This article was reprinted with permission from the Spring 2001 Cornell University Turfgrass Times (CUTT), Vol. 12, No. 1. Published by the Turfgrass Science Program at Cornell University, Ithaca, N.Y., CUTT is a free publication for members of the New York State Turfgrass Association.