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Lecture 10: Calibration and Uniform Application

In order to get the most out of a herbicide program, the herbicide must be applied accurately and uniformly. This is particularly difficult when applying granular herbicides.!

# 1 Landscape Weed Control Challenge: Proper Application!!!!

Herbicides are applied on a Per Area Basis! NOT oz per gal!

YES:

  • oz per 1000 sq. ft.
  • oz per gallon applied to 1000 sq. ft.

NO:

  • oz per gallon
  • % (exception – Roundup)
  • oz per backpack

Granules: uniform spread
Pre-measure amount for area; See table 1 for pre-measure amounts for circular landscape beds
Spread herbicide over the area in different directions at least 3 times

Sprays: Calibrate sprayer. Output per area basis! .
Maintain constant – pressure, walking speed, nozzle height. Today pretend you are a tractor!
Broadcast vs. directed; Broadcast is preferred; yet directed applications in tall trees & shrubs are practical.

Rarely do we use % by volume. Exceptions – spot applications of glyphosate, glufosinate and spray adjuvants

% = percent = # per 100

So, 2 % = 2 ounces in 100 ounces = 2.5 ounces per gallon (1 gallon = 128 ounces)

0.25% Surfactant in 1 gallon — 0.25% is 0.25 per 100

128 ounces x 0.0025 = 0.32 ounces

NOT 32 ounces!! That would be 25%

Grams of granular herbicides needed for circular landscape beds of various diameters

Grams of Product, by Recommended Rate (lb Prod/A)
Diameter
Area
80
100
125
150
200
(ft)
(ft2)
———-(grams of herbicide product)———-
4
12.6
11
13
16
20
26
6
28.3
24
29
37
55
59
8
50.3
42
52
65
78
105
10
78.6
65
82
102
123
164

Study Questions

Complete these problems and bring your work to the next class.

  1. You have a landscape bed that is approximately 0.2 acres in size. You wish to apply Surflan 4L at a rate of 4 Quarts Per Acre.
    1. How much Surflan 4L (the product) will you need to treat this bed?
    2. Your sprayer delivers 30 gallons per acre. How many gallons of spray will you need to treat this landscape bed?
    3. You are using a 4-Gallon sprayer. How much Surflan 4L will you put in the sprayer?
    4. You wish to add 2% (by volume) Roundup-Pro to this spray application. How much Roundup-Pro do you put in the 4-gallon sprayer?
  2. You wish to apply Pendulum 2G as a granular preemergence herbicide for crabgrass and goosegrass control to a landscape bed. The recommended rate of application for 150 lb product per acre.
    1. How much Pendulum 2G would be needed to treat a landscape bed that is 5000 sq. ft.?
    2. You need to calibrate your rotary spreader to achieve this rate. You measure the width of the pattern to be 10 ft, and there is a 50 ft piece of plastic. There are 454 g/lb. Determine how many grams of product should be collected on this sheet of plastic to properly calibrate the spreader.

Written By

Photo of Brandon HopperBrandon HopperBusiness and Technology Application Technician (919) 515-3705 brandon_hopper@ncsu.eduHorticultural Science - NC State University
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