UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

AUG I' 8 2015 

MEMORANDUM 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

SUBJECT: Qualitative Assessment of the Benefits of Hydrogen Cyanamide (014002) 

FROM: 

THRU: 

Sunil 

Biological 

Ratnayake

Analysis 

, Biologi

Branch 

st 

(_ 

~... ~,; A 

~ ~ \ 

~ 

Stephen Smearman, Economist p_ / ~ ~ ~~ Economic Analysis Branch ~ 

Biological and Economic Analysis Division 7503P) 

Arnet Jones, Chief d /1 /2 ~ ~ 11 .uf' 

Biological Analysis Bran~//~ l"fY 

Timothy Kiely, Chief (,}-- V\.\.t · 

Economic Analysis Branch V J ~ Biological and Economic Analysis Division (7503P) 

TO: Dana Friedman, Chemical Review Manager 

Pesticide Re-evaluation Division (7508P) 

Peer Review Panel date: March 4, 2015 

SUMMARY 

As part of the registration review process for hydrogen cyanamide, this document provides an 

assessment on the benefits and available alternatives for hydrogen cyanamide in U.S. fruit 

production. 

Hydrogen cyanamide is the only plant growth regulator (PGR) registered in the U.S. that is used 

to induce uniform bud break in fruits and berries in areas of the country where winter 

temperatures are not cold enough to induce it naturally. Uneven bud break can significantly 

reduce fruit production and lead to a lack of uniformity in fruit development, which hampers 

production practices, including pest management and harvest. 

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The economic benefits of using hydrogen cyanamide are significant in fruit producing areas 

where the critical number of chilling hours needed for bud break does not occur or is not 

consistent. In these areas, the critical chilling hours needed for bud break can be supplemented 

by the application of hydrogen cyanamide. There is no need for hydrogen cyanamide in the areas 

where the number of required chilling hours are fulfilled. Although not registered as pesticides, 

fertilizer based compounds such as calcium ammonium nitrate are used in certain areas of 

California for enhancing bud break. According to the available information, hydrogen cyanamide 

is used annually on fruits and berries such as apples, blueberries, cherries, grapes, kiwi fruit, 

peaches and plums. Use may be sporadic and depends on local conditions. Hydrogen 

cyanamide is probably not a typical input into production, with the exception of kiwifruit where 

about 30 percent of the crop is treated. 

INTRODUCTION 

Bud dormancy in deciduous woody perennials is a complex process that enables plants to survive 

long periods of adverse weather conditions. In temperate perennial species, a period of low 

temperatures, referred to as winter-chilling, is needed to release bud dormancy. This chilling 

requirement varies with the plant species, individual variety, and the area in which they are 

grown. In the areas where the chilling temperatures are marginal, hydrogen cyanarnide is 

applied to supplement the needed chilling hours to ensure uniform bud break. Other plant growth 

regulators, such as auxins, gibberellins, and cytokinins, are used for purposes such as to thin 

blossoms or to improve fruit size, quality as well as to enhance fruit ripening. They are not used 

to promote uniform bud break. 

Use of Hydrogen Cyanamide 

In fruit crops such as apples, blueberries, grapes, cherries, peaches and kiwifruit a minimum 

number of chilling hours are needed for uniform bud break and a higher yield. For example, a 

study conducted in the southern and central parts of the San Joaquin valley in California found 

that 600 hours of temperatures at or below 7°C ( 45°F) are ample for normal bud break in table 

grapes (Dokoozlian, Undated). Also, less than 50 percent bud break has been observed in 

conditions with less than 200 chilling hours at a temperature of 3°C (37°F). (Dokoozlian et al., 

1995). A separate study has reported that the 'Ruston Red' a variety of peach grown in southern 

Alabama, requires 850 hours of temperatures at or below 45°F for a peak production. Under 

conditions where the number of chilling hours range from 700 to 750 hours at or below 45°F, 

production could decline 25 percent or more, and fruit quality is diminished for this variety 

(Powell, 1999). The same study reported that applications of hydrogen cyanamide can 

effectively replace 250 to 290 chilling hours in peach production (Powell ( 1999). 

The timing of hydrogen cyanamide applications is critical to avoid yield reductions of grapes. 

Late applications of hydrogen cyanamide (less than four weeks before bud break) may injure the 

buds and reduce the bud break (Fidelibus et al., 2012). 

Data on the use of plant growth regulators in fruit and berry production are limited. While the 

infom1ation in Table I illustrates the use of hydrogen cyanamide in different states and use sites, 

it may substantially understate the extent of use. The information was compiled from three 

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different data sources and includes by use site, the states with reported usage, the average total 

amount applied annually, the average application rate, and the average percent of the crop treated 

at the national level. Use of hydrogen cyanamide was confirmed in at least five states including 

California, Georgia, North Carolina, Texas and Washington and on at least eight crops. The 

University of Florida Agricultural Extension Service also recommends the use of hydrogen 

cyanamide on blueberries for bud break (Univ. of Florida IFES, 2007). However, no usage data 

are available in Florida. 

According to available data, the top three use sites of hydrogen cyanamide, by amount of 

chemical used are: grapes, cherries, and kiwifruit grown in California. Other sites with use 

include apples, blueberries, figs, peaches and plums (Table I). 

Table 1. Average Annual Hydrogen Cyanamide Usage by State and Site (2004-2012) 

Use Site States with Average Total Average Per Average Percent Crop 

Reported Usage* Amount Application Treated Nationa lly 

Applied (lb) Rate (lb/ Acre) 

Apples California, 7,000 13.0 <1% 

Washington 

Blueberries California, Georgia, 2,000 8.2 <2.5% 

North Carolina 

Cherries California 100,000 15.0 5% 

Grapes California 100,000 5.8 5% 

Figs** California 2,000 6.2 5% 

Kiwifruit California 20,000 16.8 30% 

Peaches Texas (D) 

Plums California (D) .. Source: SLUA (EPA 2014). The data time penod was 2004-2012. Data sources include California Department of Pesticide 

Regulation (CDPR); USDA NASS and EPA proprietary Private Market Research. 

(D) =data from survey information that reponed usage but the information is not published to avoid disclosure of practices on 

individual establishments. 

• These are the states that have been surveyed and reported use. Use could occur on labeled sites in other states that are not 

captured in survey data. Due to limited data, there is some uncertainty of use for sites in states with low reported usage such as 

blueberries, peaches and plums. 

• •figs - EPA found reported use even though there appears to be no registered label use for figs or emergency exemption 

requests for the use of hydrogen cyanamide on figs in California. 

For apples, blueberries, cherries, grapes, kiwifruit, peaches and plums, hydrogen cyanamide is 

used in the dormant stage of the crop production cycle in states where consistently cold 

temperature requirements may not be met to induce bud break. Apples, blueberries, cherries, 

grapes and kiwifruit had consistent usage of hydrogen cyanamide from year to year over the 

2004 to 2012 time period. Hydrogen cyanamide appears to be especially important for kiwifruit, 

perhaps because varieties adapted to warmer winters are not available as in other fruits and 

berries (Engin, 2010). Nearly 30 percent of the kiwifruit crop grown in California is treated 

annually (Table 1 ). 

For fruit crops such as peaches, plums and blueberries grown in states other than California and 

Washington, use may be more sporadic. Although, it should be noted that BEAD's data sources 

do not regularly survey for the use of growth regulators in other states and crops. Given the 

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nature of use, however, it is likely that the need for the use of hydrogen cyanamide does not arise 

every year. However, in years and locations with atypically warm winters, use would still be 

important in crop production areas. 

Available Alternatives to Hydrogen Cyanamide 

Hydrogen cyanamide is used to induce bud break in U.S. fruit production. Other plant growth 

regulators such as auxins, gibberellins, cytokinins, and ethylene are used in the production of 

fruits and other crops to enhance the characteristics such as fruit quality, size, thinning, and fruit 

ripening (Dokoozlian, undated). Calcium ammonium nitrate (CAN-17) and other nitrogen based 

fertilizer compounds are being used in certain areas of California with marginal chilling 

temperatures for bud break in grapes and cherries (Cline, 2003; Caprile, 2009). The 

effectiveness of these materials varies depending on the application rate, application timing, 

weather conditions, adjuvant(s) included, and the planted variety (Weis, et al., 1998). These 

fertilizer based compounds are less likely to injure the crop than hydrogen cyanarnide and they 

are able to compensate for fewer chilling hours than hydrogen cyanamide (Caprile, 2009). 

However, they are not registered as plant growth regulators and crop profiles and extension 

recommendations in California and other states do not specifically identify fertilizer based 

compounds as alternative treatments for bud-breaking. Usage data are unavailable for these 

products, so it is not known how widely they are used. 

Benefits of Using Hydrogen Cyanamide 

Uneven bud break due to insufficient chilling hours can significantly reduce production and lead 

to lack of uniform1ty in fruit development, which hampers production practices, including pest 

management and harvest, and can lead to loss of yield. For example, as mentioned above, for 

Alabama peach growers that produce the Ruston Red variety, a yield loss of up to 25 percent 

could be realized if growers do not receive the minimum number of chilling days for this variety 

of peach (Powell, 1999). This is an indication of the benefits of using hydrogen cyanarnide for 

the Ruston Red and similar temperature sensitive peach varieties grown in southern climates. 

The potential yield loss in Alabama for the Ruston Red peach variety indicates potential negative 

impacts to Ruston Red peach grower gross revenues. While yield loss data for all temperature 

sensitive fruits is scarce, growers of other temperature sensitive fruits that need a minimum 

number of chilling hours to induce bud break would probably realize similar benefits to avoid 

crop loss due to variable temperature fluctuations in years when the minimum number of hours 

of chilling may not be reached. For example, with up to 30 percent of the kiwifruit crop treated 

annually with hydrogen cyanamide, it can be considered a critical use for kiwifruit growers in 

California. A yield loss of 25 percent on 30 percent of the crop area grown would be significant 

for kiwifruit growers and for kiwifruit production in the U.S. For fruit crops with a much larger 

number of acres in production nationally than kiwifruit, such as cherries and grapes, yield and 

quality losses on these crops can result in significant gross revenue impacts for cherry and grape 

growers. Based on the reported usage data in Table 1 above, both cherries and grapes have on 

average, 5 percent of their crop treated with hydrogen cyanamide annually. 

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Conclusion 

The benefits of using hydrogen cyanamide are significant in fruit producing areas where the 

critical number of chilling hours needed for bud breaking during the dormant season is not 

realized. In these areas, the use of hydrogen cyanamide can be used to supplement the critical 

number of chilling hours needed to induce uniform bud break. For growers of temperature 

sensitive varieties of tree and berry fruits, the niche use of hydrogen cyanamide to induce bud 

break can provide significant benefits through improved quality and increased yield in areas 

where the number of chilling hours may not be sufficient for uniform bud break. 

No other plant growth regulators are registered for bud break. Some nitrogen-based fertilizer 

compounds may also provide similar benefits and can be used as a non-pesticide alternative for 

hydrogen cyanarnide, at least in California. However, these products are not as effective as 

hydrogen cyanamide and are not registered as plant growth regulators. 

REFERENCES 

Caprile, J. 2009. Timing rest breaking sprays for cherry. Online Publication. Available at: 

http://ucanr.org/sites/cccoopext/files/80967.pdf . Accessed on Feb. 9, 2015. 

CDPR. 2009. Guidelines for Interpreting Pesticide Laws, Regulations, and Labeling. California 

Department of Pesticide Regulation. Online Publication. Available at: 

http://www.cdpr.ca.gov/docs/enforce/compend/vol 8/chapter7.pdf. Accessed on Feb 10, 2015. 

CDPR. Summary of Pesticide Use Report 2012, Indexed by Chemical. Online Publication. 

Available at: hnp://www.cdpr.ca.gov/docs/pur/purl2rep/chmrptl 2.pdf. Accessed on Feb 9, 

2015. 

Cli~e, H. 2003. Nitrogen compounds promote even grapevine bud break. Western Farm Press. 

Online Publication. Available at: http://westernfarmpress.com/nitrogen-compounds-promoteeven-grapevine-bud-break. Accessed on Feb 10, 2015. 

Crop Profiles for Grapes in California, 1999. Online Publication. Available at: 

http://www.ipmcenters.org/cropprofiles/docs/cagrapes-table.pdf. Accessed on Feb 10, 2015. 

Crop Profile for Kiwi in California, 2000. Online Publication. Available at: 

http://www.ipmcenters.org/cropprofiles/docs/cakiwi.pdf. Accessed on Feb. 10, 2015. 

Dokoozlian, N. K., (Undated). Plant Growth Regulator Use for Table Grapes Production in 

California. Online Publication. Available at: 

http://www2.inia.cl/medios/biblioteca/serieactas/NR26071.pdf. Accessed on Feb. 10, 2015. 

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Dokoozlian, N. K., L. E. Williams and R. A. Neja. 1995. Chilling Exposure and Hydrogen 

Cyanamide Interact in Breaking Dormancy of Grape Buds. HortSci. 30:1244-1247. 

Engin, H., Z. Gokbayrak and A. Dardeniz. 2010. Effects of Hydrogen Cyanamide n the Floral 

Morphogenesis of Kiwifruit Buds. Chilean Journal of Agricultural Research. Available at: 

http://www.scielo.cl/scielo.php?script=sci _ arttext&pid=S07 l 8-583920I0000300018 

EPA. 2014. SLUA: Screening Level Usage Assessment. Biological and Economic Analysis 

Division, Office of Pesticide Programs. 

Fidelibus M, and S. Vasquez. 2012. Using Plant Growth Regulators to Promote Budbreak in 

Grapes. University of California. Online Publication. Available at: 

http://www.extension.org/pages/33 l 04/using-plant-growth-regulators-to-promote-bud-break-ingrapes. Accessed on Feb 9, 2015. 

Powell, A. A. 1999. Action Program for Dormex Application for Peaches. Online Publication. 

Available at: http://www.aces.edu/dept/peaches/peachdormex.html. Accessed on Feb. 11 , 2015. 

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University of Florida. 2008. IFAS Extension Overview of Hydrogen Cyanamide on Blueberries; 

Online Publication. Available at: http://sfo.ucdavis.edu/files/144711.pdf. Accessed on Feb 10, 

2015. 

USDA NASS. 2014. Online Publication. Available at: 

http://guickstats.nass.usda.gov/#9872F35A-6BFB-30AF-A868-6436DEBE9295. Accessed on 

Jan. 29, 2015. 

Weis, K. G., Southwick, S.M, Yeager J. T., Rupert, M.E., and W.W. Coats. 1998. Control of 

Dormancy and Bud break in Sweet Cherry (Prunus avitum L.) cv 'Bing' with Surfactant+ 

Calcium Ammonium Nitrate and Hydrogen Cyanamide. HortScience vol. 33, no. 3: 514. Online 

Publication. Available at: http://hortsci.ashspublications.org/content/33/3/5 l 4.3 .abstract. 

Accessed on Feb. IO, 2015. 

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