Spray_Calculation_chart.docx

AG-0356-S-16-0003

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Calculations for estimating spray application of carbaryl on individual trees

1. Estimating bole surface area*

Note that this equation (& data below) assumes a smooth surface. Trees with furrowed bark (e.g., large ponderosa pines) will have a much greater surface area than calculated by this formula (e.g., 65% or more!).

Approximate bark surface area (ft2) by dbh for 30, 40, and 50 foot spray heights**

**For conifer species except pinyon pine

*Use of two inch size categories such as obtained by using a Builtmore Stick will speed data collection and summarization (e.g. category 10”dbh covers 9-11” dbh trees).

2. Calculations for mixing 2% AI solution Using the label directions, here are the approximate mixing instructions (at this date):

(From labels for Carbaryl 4L, Sevin 4F, Sevin SL, and Sevin XLR; see pages 8, 25, 10, and 27, respectively.

Thus, for 100 gallons water add approx. 4 gallons product

NOTE: 1 gallon of product with 43% active ingrediant (AI) into 25.6 gallons of water results in ~1.65% AI mixture by volume (43% AI in 1 gallon product = X% AI in 25.6 gallons water +1 gallon product; X = 44/26.6 = 1.62% AI). When calculated by weight, the label mixture is 1.8% (see pg 7, SERA 2008). This is not quite the 2% of AI recommended but is the label direction and is refered to as 2% AI in these directions. If label directions were not followed and enough water was used to make a solution of 2% product (which is only 43% AI) (e.g. 1 gallon of product into 49 gallons of water to make 50 gallons total) the level of active ingredient would be only 0.86% AI (X=43/50). Field tests show that 2% gives slightly better efficacy than 1%, although both provided 2 years of protection on lodgepole pine (Shea and McGregor 1987). A 1.7-1.8% level is considered comparable to 2% (see Johnson 1996). The 1.7-1.8% AI from the label recommendation will be called 2% AI throughout this document.

3. Estimate number of gallons of 2% AI carbaryl solution per tree size category and for project:

Formula to determine gallons of solution: ft2 bole surface/50 ft2 per gallon solution (check label for changes) e.g. for a 10”dbh tree sprayed to 40’ ht (=104 ft2 bark surface) 104 / 50 = 2.08 gallons per tree of that size for 10 trees in that size category expect to use around 21 gallons

Note the data below uses the equation assuming a smooth surface. Trees with furrowed bark such as large ponderosa pines will have a much greater surface area and use more solution than estimated below (e.g. 65% or more!).

NOTE: Each gallon of 2% AI solution contains ~0.16 lbs of carbaryl AI. (1 gallon Carbaryl4L contains 4 lbs AI; 4 gal. contain 16 lbs; diluted with 100 gallons of water = 16 lbs/100gallons) image1.emf

Microsoft_Excel_97-2003_Worksheet1.xls

USE

ESTIMATED GALLONS 2% AI CARBARYL SOLUTION PER SIZE CLASS and FOR PROJECT (contact your FHP office for more specifics.)

DBH (in) Height (ft) SQFT surface no. gal 2% AI solution (1gal/50ft2) no. trees in size category estimated gallons 2% AI solution*

8 30 62.8 1.3 0 0.0

10 35 91.6 1.8 3 5.5

12 35 110.0 2.2 15 33.0

14 35 128.3 2.6 12 30.8

16 35 146.6 2.9 6 17.6

18 40 188.5 3.8 3 11.3

20 40 209.5 4.2 5 20.9

22 40 230.4 4.6 2 9.2

24 45 282.8 5.7 1 5.7

26 45 306.3 6.1 0 0.0

28 45 329.9 6.6 0 0.0

30 50 392.8 7.9 0 0.0

32 50 418.9 8.4 0 0.0

34 50 445.1 8.9 0 0.0

36 50 471.3 9.4 0 0.0

TOTAL 134.0

*Actual gallons of solution used may vary with tree species and bark roughness, equipment used, individual applicator, environmental conditions, etc.