UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

NOV 30 2011 

MEMORANDUM 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

SUBJECT: Per-Acre Application Rates for Ornamental Trees in Urban Forests, Seed 

Treatment and Container-Grown Ornamental Uses of Pac1obutrazol 

FROM: 

THRU: 

TO: 

Jonathan 

Biological 

Becker, 

Analysis 

Ph.D., 

Branch 

Senior Science Advisor ~ . ;W~ 

Biological and Economic Analysis Division (7503P) 

Arnet Jones, Chief 

Biological Analysis Branch 

Biological and Economic Analysis Divisio 

Meghan Radtke, Ph.D., Biologist 

Edward Odenkirchen, Ph.D., Senior Advisor 

Sujatha Sankula, Ph.D., Lead Biologist 

Environmental Risk Branch I 

Environmental Fate and Effects Division (7507P) 

Khue Nguyen, Chemical Review Manager 

Neil Anderson, Chief 

Risk Management and Implementation Branch 3 

Pesticide Re-Evaluation Division (7508P) 

Peer Review Panel date: 23 November 2011 

Summary 

BEAD provides the following high-end estimates of the per-acre application rate for the 

following uses of pac1obutrazol based on the label and additional information about the 

particular use: 

Ornamental trees (in urban forests) 

• Tree injection - 0.36 lbs per acre 

• Soil injection (around base of trees) - 1.91bs per acre 

1 
• Basal drench (around base of trees) -1.91bs a.i. per acre 

Seed treatment 

• Tomato - 0.00040 lbs a.i. per acre 

• Pepper - 0.00079 lbs a.i. per acre 

• Curcurbits - 0.00029 lbs a.i. per acre 

Nursery production of container-grown ornamentals 

• 6-inch pot, spray application - 0.20 lb a.i. per acre 

• 6-inch pot, drench application - 4.3 lb a.i. per acre 

• 8-inch pot, spray application - 0.21b a.i. per acre 

• . 8-inch pot, drench application - 6.Ilb a.i. per acre 

• I8-inch by 9-inch propagation trays, spray application - 0.261bs a.i. per acre 

Background 

Paclobutrazol is a plant growth regulator that slows vegetative growth by inhibiting the 

production of gibberellin. When gibberellin is inhibited cell division still occurs, but the cells do 

not elongate resulting in a more compact plant. Additionally paclobutrazol enhances tolerance of 

the plants to environmental stresses, probably through the increased production of abscisic acid 

and the phytol component of chlorophyll (Chaney, 2005). 

In this document BEAD provides high-end estimates of the per-acre application rate for uses of 

paclobutrazol. These estimates are based on additional information about the particular use and 

label information and will be used by the Environmental Fate and Effects Division in their 

screening-level ecological risk assessment as part of Registration Review. The uses addressed 

herein are the application of paclobutrazol to ornamental trees (in urban forests), its use as a seed 

treatment, and its use in nursery production of container-grown ornamentals. 

Per-Acre Application Rates for Paclobutrazol Use on Ornamental Trees in Urban Forests 

Labels indicate that there are three application methods that can be used when applying 

paclobutrazol to ornamental trees. These include injecting the active ingredient directly into the 

tree, injecting the active ingredient into the soil around the base of the tree, and drenching the 

soil around base of the tree. The labels provide information about the amount of active 

ingredient to apply per tree of a given size. In general, the per-acre application rates for 

paclobutrazol use on ornamental trees in urban forests may be calculated using the following 

equation: 

Lbs ai Lbs ai Trees . - T * A * Conversion Factors Acre ree cre 

The following section describes other necessary informantion (number of trees per acre and their 

size) needed to complete the calculation of the per-acre application rate. 

2 
Urban Forests 

Nowak et al. (2001) regard urban forests as ecosystems characterized by the presence of trees 

and other vegetation in association with people and their developments. Spatially, urban areas 

(and the contained forest) are defined by the union of three census-defmed urban designations: 

(1) urbanized areas (populations more than 50,000); (2) places containing some urbanized areas 

within their boundaries; and (3) urban places (places with more than 2,500 people located 

outside urban areas). Areas completely surrounded by urban areas are included as well. As of 

2001, urban areas cover more than 3.5 percent of the total US land areas and contain more than 

75 percent of the US population (Nowak et al. 2001). 

Nowak et al. (2001 through 2011 and reference therein) conducted a series of studies assessing 

the effects and values of urban forests in 24 cities in the United States and Canada (Table 1). As 

part of their studies they surveyed and described the forest structure in each city. The overall 

density (trees per acres) by land use category and the distribution of tree size by diameter at 

breast height (DB H) was provided for each city. Table 1 presents the reported mean density and 

the tree size (percent of trees less than 6 inches in diameter) for each of the cities studied. A 

median value across all cities for these parameters was calculated for use in estimation of peracre rates. 

3 
Tablel. Characteristics of Trees in Urban Forests. 

Mean Tree Size 

Density (percent 

Location less than 6 Most Common Species Reference (Trees I inches A) d.b.h)1 

Atlanta, GA 111.6 NR NR Nowak et al. 2011 [A~pendix] 

Baltimore, MD· 50.8 NR NR Nowak et al. 2011 [Appendix] 

Boston,MA 33.5 NR NR Nowak et al. 2011 [Appendix] 

Calgary, Alberta 66.7 NR NR Nowak et al. 2011 [Appendix] 

Casper, WY 9.1 57.5 Plains cottonwood, blue spruce, Nowak et al. 2010d American elm 

Chicago, IL 24.3 61.2 White ash, mulberry, green ash, Nowak et al. 2010a tree-of-heaven 

Freehold, NJ 38.3 NR NR Nowak et al. 2011 [Appendix] 

Jersey City, NJ 14.4 NR NR Nowak et al. 2011 [Appendix] 

Italian cypress, scrub oak, 

Los Angeles, CA 19.9 40 laurel sumac, Mexican fan Nowak et al. 2011 

palm, Indian laurel 

Minneapolis, MN 26.2 47.3 Green ash, American elm, Nowak et al. 2006b boxelder 

Moorestown, NJ 62.1 NR NR Nowak et al. 2011 [Appendix] 

Morgantown, WV 119.2 NR NR Nowak et al. 2010a 

New Castle County, 23.9 47.6 Red maple, sweetgum, black Nowak et al. 2009 DE cherry 

NewYork,NY 26.4 42.7 Tree-of-heaven, black cherry, Nowak et al. 2007a 

sweet gum 

Oakville, Ontario 55.6 NR NR Nowak et al. 2011 [Appendix] 

Philadelphia, PA 25.1 57.5 Black cherry, crabapple, tree- Nowak et al. 2OO7b of-heaven 

Sacramento area, CA 21.3 NR NR Nowak et al. 2011 [Appendix] 

San Francisco, CA 22.5 51.4 Blue gum eucalyptus, Monterey Nowak et al. 2OO7c pine, Monterey cypress 

Scranton, PA 116.3 77.1 Red maple, gray birch, black Nowak et al. 2010b cherry, northern red oak 

Syracuse, NY 54.5 NR NR Nowak et al. 2011 [Appendix] 

Toronto, Ontario 64.9 NR NR Nowak et al. 2011 [Appendix] 

Washington, DC 49.0 56.3 American beech, red maple, Nowak et aI. 2OO6a boxelder 

Wilmington, DE 18.0 54.2 Norway maple, northern white Nowak et al. 2009 cedar, tree-of-heaven 

Woodbridge, NJ 66.5 NR NR Nowak et al. 2011 [Appendix] 

Median 35.9 54.2 (n=ll) (n=24) I d.b.h. -- Stem diameter at breast height, measured at 4.5 ft. NR -- Not Reported 

Tree injection (EPA Reg. No. 10182-90, Clipper TM 20 UL) 

Label instructions: Clipper TM 20 UL contains 2.51 percent pac1obutrazol (listed on label cover 

letter). The Pesticide Product Label System (PPLS) states that this registration has been 

transferred to Syngenta and is now identified as EPA Reg. No. 100-995. A label for this new 

4 
Registration number was not located and the original draft label as the source of label 

information. 

EPA Reg. No. 10182-90 is a tree growth retardant for ornamental trees. Ornamental trees are 

usually defined as small trees with visual impact, often having a defining feature such as flowers, 

unique foliage, or a distinctive growth habit. Three species of tree are identified on the label 

(Australian Pine, Siberian Elm, and Sweet Gum) with a note that instructions for other species 

are being developed. For these three species, the label indicates that injection holes should be 

drilled every 8 inches around the circumference of the trunk to intercept the outer sapwood and 

the formulation injected. The amount of active ingredient injected per tree varies by the number 

of injection holes and the amount of formulation injected as described in Table 2. 

T a e . bl 2 T ree SIze an d use parame t ers fi or cr lpper TM20UL 

Tree Diameter Number of Volume of Total Volume of Total grams of 

(Inches) Injection Clipper 20 UU Clipper 20 UL paclobutrazol 

(assumed equivalent Holes per injection site per tree (ml) per tree2 

toDBH)! (ml) 

8 3 50 150 4.6 

12 5 50 250 7.7 

16 6 75 450 13.8 

20 8 75 600 18.4 

24 9 75 675 20.7 

28 11 75 825 25.3 

32 13 75 975 29.9 

Source: Clipper TM 20 UL label 

1 DBH= Diameter at breast height. 

2 Total grams a.i. per tree = Total volume (ml) per tree * Density (1.22 grams per ml [Tomlin 2003]) * Percent 

product concentration (2.51 %). 

Rate Calculation: To calculate a "per-acre" rate based on these label directions, the density and 

sizes of trees in the urban settings must be known. Using median values for number of trees per 

acre and tree diameter from Table 1, along with the maximum amount of paclobutrazol applied 

to an 8-inch diameter tree from the table above yields the following per-acre application rates: 

• Per-acre application rate - 0.36 lbs per acre = Total grams ai per tree (4.6 grams) * 

Number of trees per acre (36) * Conversion factor (l pound per 453.59 grams). 

BEAD would characterize this estimate as a high-end value that would occur uncommonly 

because of the following reasons: 

• Applications using soil injections or basal drench around the base of the tree are much 

easier and faster to accomplish than are tree injections and are the preferred application 

method (Chaney 2005). 

• Soil injection around the base of the tree and basal drench also control the growth rate of 

grass around the tree, precluding mower and string-trimmer damage to trees as there is 

less need to trim close to the tree (Chaney 2005). 

5 
• Fonnulation 10182-90 contains methanol. This has resulted in cracks, weeping injection 

holes and internal wood discoloration and has reduced the use of alcohol containing 

products in forestry (Chaney 2005). 

Soil Injections (around the tree base) (EPA Reg. No. 100-1014, Pac1obutrazoI2SC) 

Label instructions: Pac1obutrazol 2SC contains 2 lbs of active ingredient per gallon of product. 

The label indicates that the required dose, calculated based on tree size and species, is to be 

injected 3 to 6 inches deep at 60 to 150 psi unifonnly around the tree. Tree species are divided 

into 6 dosage groups. The required dose ranges from 25 to 100 ml of Pac1obutrazol 2SC for a 6-

inch (DB H) tree up to 313 to 833 ml ofPac1obutrazol2SC for a 50-inch (DBH) tree 

Rate Calculation: Using median values for number of trees per acre and tree diameter from 

Appendix 1, along with the maximum amount of pac1obutrazol applied to a 6-inch diameter tree 

yields the following per-acre application rates: 

• Per-acre application rate - 1.9 lbs per acre = Amount of fonnulation applied per tree (100 

ml) * 1 gal. fonnulation per 3785.4 ml * 2lbs a.i. per 1 gal. fonnulation * Number of 

trees per acre (36). 

BEAD would characterize this estimate as a high-end value because the maximum amount of 

active ingredient per tree is used and that many small trees in urban forests are not treated with 

growth regulators. 

Basal drench (around the tree base) (EPA Reg. No. 67690-22, Profile 2SC) 

Label instructions: Profile 2SC is a tree growth regulator labels for the reduction of tenninal 

growth and pruning volume in trees not used for food production on sites such as utility rightsof-way, urban and residential environments and not-crop areas. It is fonnulated at 2lb a.i. per 

gallon. Tree species listed on the label are grouped into three application rate categories as 

follows: 

• 1 to 2 grams a.i. per inch diameter at breast height (dbh) (example - sweetgum) 

• 2 to 3 grams a.i. per inch dbh (example - elms, maple, oaks) 

• 3 to 4 grams a.i. per inch dbh (example - Bradford Pear, ash) 

The Profile 2SC label states that for basal drench, the diluted spray should be applied uniformly 

around the tree in a shallow furrow at the point of contact between the soil and the tree trunk. 

After application, the furrow should be refilled with untreated soil. 

Rate Calculation: Using the maximum application rate listed above and the median values for 

number of trees per acre and tree diameter from Appendix 1, yields the following per-acre 

application rates: 

• Per-acre application rate - 1.9lbs a.i. per acre = Grams ai applied per inch DBH (4) * 

Median DBH (6) * 1 pound per 453.59 grams * Number of trees per acre (36). 

6 
BEAD would characterize this estimate as a high-end value as is described in the soil injection 

use above. 

Per-Acre Application Rates for Paclobutrazol Use as a Seed Treatment 

Paclobutrazol2SC may be applied to tomato, pepper, and cucurbit seeds using a variety of 

methods (e.g., slurrys, film coatings). The label reports the amount of active ingredient 'to be 

applied per seed and the seeding rate per acre must be known to calculate a per-acre application 

rate. 

Seed Treatment (tomato, pepper, cucurbit) (EPA Reg. No. 100-1014, Paclobutrazol2SC) 

Label instructions: Paclobutrazol 2SC contains 2 lbs of active ingredient per gallon of product. 

Paclobutrazol 2SC may be applied to tomato, pepper, and cucurbit seeds using a variety of 

procedures using slurrys, film coatings, and direct application. The treated seeds are then direct 

seeded or used to produce transplants. The following rates are used: 

• Tomato - 1 to 12.5 micrograms a.i. per seed 

• Pepper -1 to 16 micrograms a.i. per seed 

• Crncurbits - 1 to 6.5 micrograms a.i. per seed 

Rate Calculation: Becker and Ratnayake (2011) provide seeding rates (seeds per acre) for these 

three crops as shown in the calculations below. The per-acre application rate may be calculated 

by following formula: 

lbs a. i. 

Acre 

ug a. i. 1 pound a. i. Seed or transplants - ~--- x x ---------------- seed 453,592,370 ug a. i. Acre 

Using the mean seeding rates for these three crops from Becker and Ratnayake (2011), the 

following rates are calculated: 

• Tomato - 0.00040 lbs a.i. per acre = (12.5 flg a.i. per seed * 1 lb a.i. per 453,592,370 flg 

a.i. * 14,400 seeds per acre) 

• Pepper - 0.00079 lbs a.i. per acre = (16 flg a.i. per seed * 1 lb a.i. per 453,592,370 flg a.i. 

* 22,400 seeds per acre) 

• Curcurbits - 0.00029 lbs a.i. per acre = (6.5 flg a.i. per seed * 1 lb a.i. per 453,592,370 flg 

a.i. * 20,200 seeds per acre) 

BEAD characterizes theses results as high-end values for the following reasons: 

• Maximum application rate per seed is used for all three crops. 

7 
• Includes planting densities across the US for all end uses of the crop. Often crops 

intended for processing are planted at higher densities than that intended for fresh 

markets. 

• The range of the number of seeds per acre given in Becker and Ratnayake (20011) is 

upwardly biased because the presented values are based on the minimum row width and 

the maximum number of seeds per row foot. Grower plant to an overall density per-acre 

based on local conditions and experience, so as the row width shrinks, typically the 

distance between seeds increases (and visa versa). 

• In the case of curcurbits, only the seeding rates for cucumbers and summer squash were 

considered here. If pumpkins and melons were to be included the mean number of seeds 

per acre would be substantially lower as these crops have more widely spaced plantings. 

Per-Acre Application Rates for Paclobutrazol Use on Nursery Grown Ornamentals 

The equivalent per-acre application rates may be calculated using the following general equation: 

Lb a. i. 

Acre 

Oz. Spray 1 Gal. Spray Oz. Formulation 1 Gal. Formulation - ----~.~- x x ------------- x ------~--~---- Contazner 128 oz. Spray Gal. Spray 128 oz. Formulation 

1.0 gm a. i. 1 lb a. i. Containers 

x x x --------- Gal. Formulation 453.59 gm a. i. Acre 

BEAD based the per-acre application rate estimates on the following assumptions, which when 

taken together, result in a reasonable high-end screening estimate: 

• The treatment of container-grown plants occurs in the greenhouse at the maximum label 

application rate. 

• Once moved to outdoor plant beds all of the active ingredient is assumed to remain 

available for off-site transport. This is a very conservative assumption as ancymidol (ARestTM, AbideTM) is rapidly absorbed by the plant, and plants either sprayed or drenched 

with this chemical can be watered as soon as 1 hour after application without reduction in 

efficacy. In comparison other PGRs, such as daminozide (B-NineTM) are absorbed more 

slowly, requiring 4 hours for complete absorption (Bailey and Whipker, 1998). 

• Containers are placed outdoors in plant beds at the highest density possible while 

allowing for normal nursery operations (such as irrigation, fertilization, scouting, etc.). 

The highest density possible is termed "can tight" in the nursery industry. 

• The layout of the nursery is typical for operations producing container-grown 

ornamentals. 

Soil drench and bench sprays (potted ornamentals) (EPA Reg. No. 100-1079, Bonzi® II) 

Label instructions: Bonzi® II contains 0.036 grams active ingredient per fluid ounce of product. 

Bonzi® II may be applied as either a spray or as a drench. To make a spray or drench solution 

for a specific ornamental species, the user prepares the solution to be applied based on the 

concentration needed (e.g., 1 fluid ounce of formulated product mixed with a gallon of water will 

8 
produce a 10 ppm solution) and determines the amount to apply based on the method of 

application (foliar spray or drench), plant species being treated, and the size of the pot containing 

the plant. Table 3 identifies the types of ornamentals specified on the Bonzi® II label and the 

recommended concentrations. 

Table 3. Types of ornamentals and recommended concentrations on the Bonzi® II label. 

Plant Type Cone. Of Spray (ppm) Cone. Of Drench BEAD Comments 

(ppm) , 

Azaleas (Florist) toO to 200 ppm 5 to 15 ppm 

Bedding Plants 5 to 90 ppm 1 ppm Usually moved from greenhouse 

directly to retail sales. 

Bedding Plant Plugs 1 to 20 ppm Not recommended 

Bulb Crops "least desirable method" 5 to 200 ppm Usually moved from greenhouse 

directly to retail sales. 

Pot Chrysanthemums 50 to 200 ppm 1 to 4 ppm 

Flowering and Foliage 30 to 50 ppm 1 to 2 ppm 

Plants 

Geraniums toto 30 ppm "make with caution" 

Hibiscus 30 to 150 ppm 4 ppm 

Poinsettias to to 30 ppm (15 to 45 2 to 4 ppm Usually moved from greenhouse 

ppm inFL) directly to retail sales. 

Woody Landscape Plants 100 ppm 4 ppm 

Rate Calculation: 

• Bench Sprays - Plants in containers are places as closely as possible on the bench and 2 

to 3 quarts of spray volume per 100 square feet is applied. Four hundred 6-inch diameter 

containers can be packed onto a 100 square foot bench (5 ft. by 20 ft.). Approximately 

79 percent of the applied spray will be deposited in the containers (area of containers 

[400*1t*i (78.5 sq. ft.) -:- area sprayed (100 sq. ft.) =78.53 percent]. This produces an 

application volume per 6-inch container of 0.188 fluid ounce per pot (0.785 * 3 quarts 

spray per 100 square feet * 32 fluid ounces per quart * 100 square feet per 400 pots). 

Similarly, assuming that 224 8-inch containers can be placed on a 100 square foot bench 

(4 ft. by 25 ft.), the application volume per 8-inch container is 0.337 fluid ounces per pot. 

Finally, assuming that 88 liner trays may be placed on a 100 square foot bench, the 

application volume per tray is 1.1 fluid ounces (3 quarts spray per 100 square feet * 32 

fluid ounces per quart * 100 square feet per 88 trays) [All of the applied spray is assumed 

to be d~posited in the tray containers] 

• Drenches - The label includes a table of volumes based on the size of the container to be 

applied to each pot. For example, 4 fluid ounces is applied to a 6-inch pot and 10 fluid 

ounces is applied to an 8-inch pot. 

Size of containers: Although the American Nursery and Landscape Association (ANLA, 2004) 

has done much to standardize the nomenclature for the sizes of containers used in ornamental 

productions, considerable variability remains. For example, a "#1" container is specified to 

9 
contain between 152 and 251 cubic inches (0.65 to 1.08 gallons) by ANLA (2004). Dimensions 

of a #1 container vary, with top diameters ranging from 6 inches to 8 inches. "Azalea pots" 

contain 132 cubic inches and typically measure 5718 (diameter) by 4718 inches (height). The 

dimensions of propagation liner trays are 18 3/8 (W) x 9 3/16 and contain either 18 (i.e., 3 x 6) or 

32 (i.e., 4 x 8) square cavities (Nursery Supplies 2011). Approximately 88 trays can be placed 

on a 100 square foot bench (6 feet x 16213 feet). 

Container Nursery Layout: Typical production areas are designed to allow for the orderly 

movement of plants into and out of the areas by workers and to allow access for the care of these 

plants. Yeager and Ingram (2010) describe typical production areas for nurseries. These areas all 

have plant beds that are 8 feet wide separated by 2 foot Walkways. Equipment access is provided 

by a narrow road (10 to 20 feet wide) every 100 feet between the plant beds and by a 30-foot 

wide perimeter road. This layout results in the production area with approximately 50 % of the 

area consisting of plant beds, with the remaining area in service roads and access paths. For the 

operation as a whole, this estimate does not account for propagation areas, media preparation and 

storage areas, service areas (equipment storage and repair facilities, chemical storage areas, 

offices), employee facilities, and shipping areas. It should be noted that these typical dimensions 

are often modified based on local conditions. 

Estimates of the per-acre number of containers: Based on the layout described by Yeager and 

Ingram (2010) and assuming the highest density possible ("can tight") of 6-inch containers (i.e., 

4 per square foot) in the plant bed area (50 percent of the total area), the overall density is 87,120 

containers per acre. Using 8-inch containers, the overall density would be about 49,000 

containers per acre. Using 18-inch by 9-inch trays, the overall density would be about 19,360 

trays per acre (43,560 square feet per acre * 50% in plant beds * 1 tray per 1.125 square feet). 

Each lO-inch x 20-inch seeding tray has a surface area of 200 square inches (=1.389 square feet 

and overall density would be 15,680 trays per acre (43,560 square feet per acre * 50% in plant 

beds * 1 tray per 1.389 square feet). 

Robbins (no date), in his discussion on starting a wholesale nursery, estimated that the average 

number of containers per acre, including the requirements for roads, aisles, and buildings in the 

operation is 110,000 to 130,000 I-gal containers I Acre. Hinson et al. (2011) in their study of 

estimating the cost of producing selected ornamental crops used 30,000 plants per acre (azaleas 

in one-gallon container) as the estimate of the number of plants in a high density production 

scenario. Neither author provided a basis for the number of containers per acre. 

These three studies support densities ranging from 30,000 to 130,000 #1 containers per-acre. 

The large ranges of these values reflect the variability in nursery layout based on local and 

regional conditions and as well as the variability in the sizes of nursery containers as described 

above. BEAD recommends using values of 87,120 (6-inch container), 49,000 (8-inch container), 

and 19,360 (9-inch x 18-inch propagation tray) for calculation of per-acre application rates. 

Equivalent per-acre application rates: Using the equation presented earlier and assuming a "cantight" number of containers per acre and the maximum application rates, the equivalent per-acre 

application rates are: 

• 6-inch pot, spray application - 0.20 lb a.i. per acre = (0.188 oz. spray per 6-inch container 

* 1 gal. spray per 128 oz. spray * 20 oz. formulation per gallon spray * Igal. formulation 

10 
per 128 oz. fonnulation * 4.608 grams a.i. per gal fonnulation * 1 pound per 453.59 

grams * 87,120 6-inch contaiI.lers per acre). 

• 6-inch pot, drench application - 4.3 lb a.i. per acre = (4 oz. drench per 6-inch container 

* 1 gal. spray per 128 oz. spray * 20 oz. fonnulation per gallon spray * 1 gal. fonnulation 

per 128 oz. fonnulation * 4.608 grams per gal. fonnulation * 1 pound per 453.59 grams * 

87,120 6-inch containers per acre). 

• 8-inch pot, spray application - 0.2 lb a.i. per acre = (0.337 oz. spray per 8-inch container 

* 1 gal. spray per 128 oz. spray * 20 oz. fonnulation per gallon spray * 1 gal. fonnulation 

per 128 oz. fonnulation * 4.608 grams per gal. fonnulation * 1 pound per 453.59 grams * 

49,000 8-inch containers per acre). 

• 8-inch pot, drench application - 6.11b a.i. per acre = (10 oz. drench per 8-inch container 

* 1 gal spray per 128 oz. spray * 20 oz. fonnulation per gallon spray * 1 gal. fonnulation 

per 128 oz. fonnulation * 4.608 grams per gal. fonnulation * 1 pound per 453.59 grams * 

49,000 8-inch containers per acre). 

• 18-inch by 9-inch propagation trays, spray application - 0.261bs a.i. per acre = (1.1 oz. 

spray per 18-inch by 9-inch tray * 1 gal. spray per 128 oz. spray * 20 oz. fonnulation per 

gallon spray * 1 gal. fonnulation per 128 oz. fonnulation * 4.608 grams per gal. 

fonnulation * 1 pound per 453.59 grams * 19,360 18-inch by 9-inch trays per acre). 

BEAD characterizes these application rates as high-end values because of the use of maximum 

application rate per container and highest density of containers in the plant beds. 

Pre-plant plug I liner soak and Pre-plant bulb soaks (EPA Reg. No. 400-515, Paczol®) 

Label instructions: The label for Paczol® contains instructions for the pre-plant application for 

plugs, liners and bulbs as a soak. Specific use rates are not given for this method because the 

rate is influenced by varying soak times, the extent of rooting of each plant, the media moisture 

levels, the differing sensitivities of cultivars and species being treated, cultural practices and 

environmental factors. 

BEAD does not have infonnation to be able to calculate a per-container application rates and 

therefore cannot calculate an equivalent per-acre application rate. 

However, the equivalent per-acre application rate for this application method should be 

encompassed by that calculated for the soil drench or bench spray applications to container 

grown ornamentals. The Paczol® label states under "Detennining Optimum Rates" that the rates 

recommended are ranges and should be used only as a guideline. This is followed by the 

statement "Do not exceed the maximum recommended rate". Since the calculation of the 

application rate for the soil drench and bench spray application methods for container grown 

ornamanetals use the maximum application rate, the soak application method will not exceed this 

rate. 

Further, the pre-plant soak method for treatment of plug / liners and bulbs are most frequently 

used when preparing containers for the retail market. It would be unusual for these containers to 

be placed on outside plant beds prior to their shipment. 

11 
References 

ANLA. 2004. American Standard for Nursery Stock. American Nursery and Landscape 

Association. ANSI Z60.1-2004. 

Bailey, D.A. and B.E. Whipker. 1998. Best Management Practices for Plant Growth Regulators 

Used in Floriculture. Horticulture Information Leaflet # 529. North Carolina 

Cooperative Extension Service. 

Becker, J. and S. Ratnayake. 2011. Acres Planted per Day and Seeding Rates of Crops Grown 

in the United States. Memo to P. Deschamp, Health Effects Division and D. Spatz, 

Environmental Fate and Effects Division, Office of Pesticide Programs. 

Chaney, W.R. 2005. Growth Retardants: A Promising Tool for Managing Urban Trees. 

Purdue University Extension. FNR-252-W. 

Hinson, R.A., R.D. Little, K.E. Hood, A. Owings, R. Harkess, and J. Black. 2011. Estimating 

the Cost of Producing Selected Ornamental Crops in Plant Hardiness Zones 8 and 9. 

Journal of the American Society of Farm Managers and Rural Appraisers, Vol. 74, No.1, 

Pg.3-22. 

Latimer, J.G. 2009. Selecting and Using Plant Growth Regulators on Floricultural Crops. 

Publication 430. Virginia Cooperative Extension, Virginia Tech, Blacksburg, V A. 

Nowak, D.J., M.H. Noble, S.M. Sisinni, and J.F. Dwyer. 2001. People & trees: assessing the 

US urban forest resource. Journal of Forestry 99(3): 37-42. 

Nowak, DJ., R.E. Hoehn III, D.E. Crane, J.C. Stevens and c.L. Fisher. 201Oa. Assessing urban 

forest effects and values, Chicago's urban forest. United States Department of 

Agriculture, Forest Service, Northern Research Station Resource Bulletin NRS-37. 

Nowak, DJ., R.E. Hoehn III, D.E. Crane, J.C. Stevens and J.T. Walton. 2006a. Assessing urban 

forest effects and values, Washington, D.C.'s urban forest. United States Department of 

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