Rates for Application on a Per-tree Basis
Calibrating a sprayer to treat trees is similar to doing it for a plot, except the application rate per tree is determined rather than the rate per acre. Follow these steps:
1. Select the desired application rate per acre and divide by the number of
trees planted per acre. This will give the amount of spray to apply to each
Example: The trees are planted on a 6-by-6-foot spacing and it is desired to spray at the rate of 100 gallons per acre. The number of trees per acre is the area (43,560 square feet per acre) divided by the space occupied by each tree (6 feet by 6 feet = 36 square feet) or 1,210 trees per acre. Divide the desired application rate per acre (100 gallons per acre) by the number of trees (1,210) and determine the amount for each tree (0.08 gallon per tree).
2. Determine the output of the sprayer (gallons per minute) by spraying into
a container for a period of time such as 5 minutes.
Example: Spraying into a bucket for 5 minutes produces 6 quarts or 1.5 gallons. Dividing by the number of minutes gives a throughput rate of 0.30 gallons per minute.
3. Determine the length of time to spray each tree by dividing the gallons
per tree by the throughput rate.
Example: Given the information above, divide 0.08 gallons per tree by 0.30 gallons per minute to get 0.26 minutes or 16 seconds per tree. Spray each tree for about 16 seconds.
4. Practice spraying with water while someone times you until you can consistently come close to spraying each tree for the proper amount of time and, thus, apply the proper amount of chemical. Recheck your timing an hour later.