NC State Extension Publications

Determining Formulation Per Acre in a Christmas Tree Field to Achieve Target Ai Per Acre

Backpack Mistblower and Tristar Example

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  1. Determine how many trees per planted acre farmer has (see inset)
  2. Determine the volume of spray per tree:
    1. Fill up mistblower with known amount of water
    2. Spray the complete amount of water at trees as if you were treating. This is called ‘volume of spray disbursed’
    3. Count the number of trees you treated
  3. Determine the volume of spray per acre of trees:
    1. Multiply volume of spray disbursed by number of planted trees in an acre
    2. Divide that number by number of trees treated
  4. Read formulation label
  5. If target Ai per acre is in lbs per acre, convert to ounces per acre so farmer can more easily measure material
  6. Determine target oz of formulation per acre by dividing target oz of Ai per acre by % Ai in formulation.
  7. Determine oz of formulation per volume to spray in backpack mistblower by dividing 6 by 3
Worker stands near curb spraying small trees with backpack mistblower

Backpack Mistblower

Example

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  1. Determine how many trees per planted acre farmer has (see inset)
    in this example the farmer has 5 x 5 spacing, so 1742 trees per acre

    Trees per planted acre

    Formula:

    ft2 in an acre ÷ ft2 spacing

    1 acre = 43560 ft2

    4 × 4 spacing = 16 ft2

    43560 ft2 ÷ 16 ft2 = 2722 trees per planted acre

    4.5 ×4.5 spacing = 20.25 ft2

    43560 ft2 ÷ 20.25 ft2 = 2151 trees per planted acre

    5 × 5 spacing = 25 ft2

    43560 ft2 ÷ 25 ft2 = 1742 trees per planted acre

  2. Determine the volume of spray per tree:
    1. Fill up mistblower with known amount of water. 3 gallons
    2. Spray the complete amount of water at trees as if you were treating. This is called ‘volume of spray disbursed’
    3. Count the number of trees you treated
      100 trees are sprayed with 3 gallons of water with backpack mistblower
  3. Determine the volume of spray per acre of trees:
    1. Multiply volume of spray disbursed by number of planted trees in an acre
    2. Divide that number by number of trees treated

      \(\frac{\mathrm{Volume\ of\ spray\ disbursed}}{\mathrm{Number\ of\ trees\ treated}}=\frac{\mathrm{X} }{\mathrm{number\ of\ trees\ per\ acre}}\)

      \(\frac{3\ \mathrm{gallons}}{100\ \mathrm{trees}}=\frac{X\ \mathrm{gallons} }{1742}\)

      \(\left(100\right)\left(X\right)=\left(3\right)\left(1742\right)\)

      \(100X=5226\) or 52.26 gallons per acre

  4. Read formulation label:
    Tristar:
    8.5% Ai in formulation (weight)
    .76 lbs Ai per gallon (volume)
    Target Ai per acre: .154 lbs Ai per acre (weight)
  5. If target Ai per acre is in lbs per acre, convert to ounces per acre so farmer can more easily measure material
    .154 lbs Ai per acre*(16 oz/ 1lb) = 2.46 oz target Ai per acre
  6. Determine target oz of formulation per acre by dividing target oz of Ai per acre by % Ai in formulation.
    2.46 target Ai per acre ÷ .085 = 28.98 oz of Tristar formulation.
    To achiever our target Ai (2.64 oz per acre) farmer must spray 28.98 oz Tristar formulation per acre with the farmer’s backpack mistblower
  7. Determine oz of formulation per volume to spray in backpack mistblower by dividing 6 by 3
    28.98 oz Tristar per acre ÷ 52.26 gallons per acre sprayed by backpack mistblower in 5*5 spacing = .554 oz per gallon

Therefore, the farmer in this example must add ~.5 oz of Tristar per gallon in a Stihl backpack mistblower in order to apply target .154 Ai per acre

Authors

County Extension Director and Extension Agent, Agriculture - Horticulture
Extension Specialist, Mountain Conifer IPM
Forestry & Environmental Resources

Find more information at the following NC State Extension websites:

Christmas Trees

Publication date: March 6, 2024

Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by NC State University or N.C. A&T State University nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your local N.C. Cooperative Extension county center.

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This publication printed on: April 27, 2024

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