National Organic Standards Board 

Crops Subcommittee 

Petitioned Material Proposal 

Kasugamycin for Plant Disease Control 

July 20, 2021 

Summary of Petition: 

Kasugamycin is an antibiotic that inhibits bacterial protein synthesis and has been approved by the U.S. 

Environmental Protection Agency (EPA) for control of plant diseases, especially fire blight caused by 

Erwinia amylovora on apples and pears. The registered formulations are Kasumin 2L and Kasumin 4L 

containing the active ingredient kasugamycin hydrochloride hydrate. Kasugamycin is obtained by 

aerobic fermentation of the microorganism Streptomyces kasugaensis. The technical grade active 

ingredient, kasugamycin hydrochloride hydrate, was registered with the EPA in 2014 and a formulation 

Kasumin 2L containing two percent kasugamycin was registered in 2018. In 2020 Kasumin 4L containing 

four percent kasugamycin was registered with the EPA. Kasumin 2L and 4L were registered with a 

number of restrictions including those that prohibit application where animals are grazing or in areas 

where crops have been fertilized with animal or human waste. Users are also required to follow a 

resistance management plan. Applications are limited to four per year with California limiting 

applications to two per year. 

Summary of Review: 

Kasugamycin is an aminoglycoside antibiotic that is manufactured through fermentation and isolated as 

hydrochloride. Kasugamycin is a colorless solid at room temperature and is soluble in water. The 

hydrochloride has relatively low volatility and does not volatilize readily from soil into the air. 

Kasugamycin is characterized by the EPA as moderately persistent to persistent. A major source of 

degradation is aerobic microbial metabolism in soil with a half-life of 43-73 days. About 4% remains 

after a year. Hydrolysis in water is very slow and metabolites are also persistent (TR 278). Persistence 

on fruit is low and about half the amount applied to foliage ends up on the soil and non-target surface 

vegetation. Residues on fruit decrease 10-fold in 27-32 days. 

Kasugamycin has low acute toxicity to mammals and is classified EPA Category IV (least toxic, no warning 

label) for all exposures other than dermal, for which it is classified EPA Category III (next least toxic, 

requires "Caution" warning on label). It also has low chronic toxicity from rat feeding studies and there 

was no evidence of carcinogenicity in mice or was there evidence of chromosome damage. 

Normal labeled use of kasugamycin has led to field resistance in several pathogens. Kasugamycin was 

first used to control diseases of rice in Japan starting in 1965 with rice blast caused by Magnaporthe 

grisea and resistance was noticed in 1971. Field resistance in Acidovorax sp. occurred in 1990 and in B. 

glumae in 2001. In Florida, rapid field resistance to bacterial spot of tomato caused by Xanthomonas 

perforans was also seen. In orchards that had been treated at least once with kasugamycin studies 

found resistant bacteria in 401 field isolates from apple flowers, leaves and soil samples. Additionally, 

Erwinia resistance to kasugamycin has been generated in the laboratory. Kasugamycin has not been 

evaluated to determine if its use for orchard sprays would lead to kasugamycin-resistant pathogens in 

animals grazing orchard grass, but spraying orchard grass with streptomycin at concentration levels used 

for fire blight leads to an increase in antibiotic-resistant human pathogens found in sheep grazing on 

sprayed grass. (TR 805). 

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The TR contractor was asked to answer the question, “is kasugamycin susceptible to development of 

resistance with normal (labeled) use?” It was reported (TR 1152) that some level of resistance has 

occurred, and this is why the Kasumin label requires a resistance management plan. The plan includes 

use of kasugamycin as part of an IPM program and less than four applications per year (2 in California). 

The alternative to kasugamycin is an integrated organic program that attacks fire blight at every point in 

its life cycle. Cultural controls can be combined with application of fixed copper sprays in dormant and 

pre-bloom periods, application of lime sulfur for mildew control and thinning of apple blossoms, 

biological controls such as Aureobasidium pullulans products during bloom time, and bio-control 

antagonists such as Bacillus subtilis products later in the blooming period. Other organic procedures are 

also available to control fire blight, but they are more effective on the West Coast. 

Summary of Review: 

Category 1: Classification 

1. For CROP use: Is the substance Non-synthetic or X Synthetic? 

Is the substance formulated or manufactured by a process that chemically changes a substance 

extracted from naturally occurring plant, animal, or mineral sources? [OFPA §6502(21)] If so, 

describe, using NOP 5033-1 as a guide. 

Kasugamycin is an aminoglycoside antibiotic that is manufactured through fermentation and 

isolated as hydrochloride. Kasugamycin is a colorless solid at room temperature and is soluble 

in water. The hydrochloride has relatively low volatility and does not volatilize readily from soil 

into the air. 

2. Reference to appropriate OFPA category: 

Is the substance used in production, and does it contain an active synthetic ingredient in the 

following categories: [§6517(c)(1)(B)(i)]; copper and sulfur compounds; toxins derived from 

bacteria; pheromones, soaps, horticultural oils, fish emulsions, treated seed, vitamins and 

minerals; livestock parasiticides and medicines and production aids including netting, tree wraps 

and seals, insect traps, sticky barriers, row covers, and equipment cleansers; or (ii) is used in 

production and contains synthetic inert ingredients that are not classified by the Administrator 

of the Environmental Protection Agency as inerts of toxicological concern? 

The National Organic Standards Board (NOSB) was petitioned to add kasugamycin as an allowed 

synthetic to the synthetic substances National List at 7 CFR §205.601. Kasugamycin does 

contain an active synthetic ingredient: toxins derived from bacteria, as it is isolated from 

bacterial fermentation. 

Category 2: Adverse Impacts 

1. What is the potential for the substance to have detrimental chemical interactions with other 

materials used in organic farming systems? [§6518(m)(1)] 

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Kasugamycin is an antibiotic that inhibits bacterial protein synthesis and would not be 

expected to have chemical interactions with other materials used in organic farming. 

2. What is the toxicity and mode of action of the substance and of its breakdown products or any 

contaminants, and their persistence and areas of concentration in the environment? 

[§6518(m)(2)] 

Kasugamycin is characterized by the EPA as moderately persistent to persistent. A major source 

of degradation is aerobic microbial metabolism in soil with a half-life of 43 - 73 days. About 4% 

remains after a year. Hydrolysis in water is very slow and metabolites are also persistent (2021 

TR 278). Persistence on fruit is low and about half the amount applied to foliage ends up on the 

soil and non-target surface vegetation. Residues on fruit decrease 10-fold in 27-32 days. 

3. Describe the probability of environmental contamination during manufacture, use, misuse or 

disposal of such substance? [§6518(m)(3)] 

The probability of environmental contamination during manufacture is low because it is 

confined within a facility as a fermentation product. Kasugamycin is characterized as 

moderately persistent to persistent (U.S. EPA 2013). A major source of degradation is aerobic 

microbial metabolism in soil with a half-life of 43-73 days. About four percent remains after a 

year. Because laboratory studies used only one soil type, the EPA uses a 219-day soil half-life in 

persistence calculations (U.S. EPA 2013). Both aerobic and anaerobic degradation occurs. 

Aerobic degradation is faster than anaerobic. Typical aerobic half-life in water is seven days and 

half-life in sediment is 108 days. Anaerobic half-life was 32 days in water and 141 days in 

sediment (NYS 2015; U.S. EPA 2013). Hydrolysis in water is very slow, especially in acidic 

conditions (NYS 2015). Kasugamycin moves freely in sandy soil, less so in clay soils. It is likely to 

move both into surface water and ground water, but movement into ground water is less likely 

(U.S. EPA 2013). Because of soil movement, field dissipation is faster than molecular 

degradation seen in the laboratory. Field dissipation half-life in soil is 5.7 to 12.3 days. It does 

not volatilize readily from water or soil. Half-life of Kasugamycin in the gas phase is 1.6 hours 

(NYS 2015) (TR 264). 

4. Discuss the effect of the substance on human health. [§6517(c)(1)(A)(i); §6517(c)(2)(A)(i); 

§6518(m)(4)] 

Kasugamycin has low acute toxicity to mammals and is classified EPA Category IV (least toxic, 

no warning label) for all exposures other than dermal, for which it is classified EPA Category III 

(next least toxic, requires "Caution" warning on label). It also has low chronic toxicity from rat 

feeding studies and there was no evidence of carcinogenicity in mice or was there evidence of 

chromosome damage. 

Normal labeled use of kasugamycin has led to field resistance in several pathogens. 

Kasugamycin was first used to control diseases of rice in Japan starting in 1965 with rice blast 

caused by Magnaporthe grisea and resistance was noticed in 1971. Field resistance in 

Acidovorax sp. occurred in 1990 and in B. glumae in 2001. In Florida, rapid field resistance to 

bacterial spot of tomato caused by Xanthomonas perforans was also seen. In orchards that had 

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been treated at least once with kasugamycin studies found resistant bacteria in 401 field 

isolates from apple flowers, leaves, and soil samples. Additionally, Erwinia resistance to 

kasugamycin has been generated in the laboratory. Kasugamycin has not been evaluated to 

determine if its use for orchard sprays would lead to kasugamycin-resistant pathogens in 

animals grazing orchard grass, but spraying orchard grass with streptomycin at concentration 

levels used for fire blight leads to an increase in antibiotic-resistant human pathogens found in 

sheep grazing on sprayed grass. (2021 TR 805). 

The TR contractor was asked to answer a question about kasugamycin’s susceptibility to 

development of resistance with normal (labeled) use. It was reported (2021 TR 1152) that some 

level of resistance has occurred, and this is why the Kasumin label requires a resistance 

management plan. The plan includes use of kasugamycin as part of an IPM program and less 

than four applications per year (Two in California). 

5. Discuss any effects the substance may have on biological and chemical interactions in the 

agroecosystem, including the physiological effects of the substance on soil organisms (including 

the salt index and solubility of the soil), crops and livestock. [§6518(m)(5)] 

Up to five percent of applied amounts of kasugamycin move into surface water. Kasugamycin 

had the largest harmful effect on aquatic plants, especially blue-green algae. For duckweed, 

Lemna gibba, frond count was reduced with EC50 = 86 ppm. For green algae, 

Pseudokirchneriella subcapitata, 96-hour cell density was reduced with EC50 of 3.9 ppm. For 

blue-green algae, Anabaena flos-aquae, 96-hour cell density was reduced with EC50 of 0.65 

ppm (NYS 2015). The most sensitive plant tested was blue-green algae, Anabaena sp., with EC50 

0.65 ppm and a no-observed-adverse-effect concentration (NOAEC) of 0.08 ppm (U.S. EPA 

2013). Kasugamycin water contamination measured in rice paddy irrigation water was <2 ppm 

(Sheu et al. 2010). Huang et al. (2010) noted bacterial population changes when adding 

kasugamycin at high rates to river water microcosms in the laboratory. The EPA states that 

Kasugamycin is classified as practically non-toxic to freshwater and estuarine/marine fish and 

invertebrates on an acute exposure basis (U.S. EPA 2013). 

6. Are there any adverse impacts on biodiversity? (§205.200) 

Yes. There are subtle changes in the microbial population as some bacterial species develop 

kasugamycin resistance. As was stated in an earlier section, in orchards that had been treated 

at least once with kasugamycin studies found resistant bacteria in 401 field isolates from apple 

flowers, leaves and soil samples. It is also postulated that the microbial flora of animals that 

have grazed in orchards sprayed with kasugamycin could develop resistance as has been shown 

for other aminoglycoside antibiotics. Negative changes in the soil microflora are not in 

concordance with OPFA criteria for listing on the National List. 

Category 3: Alternatives/Compatibility 

1. Are there alternatives to using the substance? Evaluate alternative practices as well as nonsynthetic and synthetic available materials. [§6518(m)(6)] 

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The alternative to kasugamycin is an integrated organic program that attacks fire blight at every 

point in its life cycle. Cultural controls can be combined with application of fixed copper sprays 

in dormant and pre-bloom periods, application of lime sulfur for mildew control and thinning of 

apple blossoms, biological controls such as Aureobasidium pullulans during bloom time, and biocontrol antagonists such as Bacillus subtilis later in the blooming period. Other organic 

procedures are also available to control fire blight, but they are more effective on the West 

Coast. 

2. In balancing the responses to the criteria above, is the substance compatible with a system of 

sustainable agriculture? [§6518(m)(7)] 

Kasugamycin has been in agricultural use since 1965. It has been used against a number of plant 

pathogens. In every instance, some level of resistance has occurred (Vallad et al. 2010; Yoshii et 

al. 2012). The EPA believes that resistance of the fire blight pathogen Erwinia amylovora to 

kasugamycin is possible, and the Kasumin label requires a resistance management plan. This 

plan includes use of kasugamycin as part of an IPM program and less than four applications per 

year (U.S. EPA 2018). (2021 TR 1145 

Given the history that antibiotics used in agriculture create microbial resistance, and that the 

NOSB has voted to remove other antibiotics in the same family, such as streptomycin, from the 

National List, the Crops Subcommittee finds that kasugamycin, is not compatible with a system 

of sustainable agriculture under OPFA criteria. 

Classification Motion: 

Motion to classify kasugamycin as synthetic 

Motion by: Rick Greenwood 

Seconded by: Steve Ela 

Yes: 8 No: 0 Abstain: 0 Absent: 0 Recuse: 0 

National List Motion: 

Motion to add kasugamycin to the National List at §205.601(j)(4) for plant disease control 

Motion by: Rick Greenwood 

Seconded by: Amy Bruch 

Yes: 0 No: 8 Abstain: 0 Absent: 0 Recuse: 0 

Approved by Rick Greenwood, Crop Subcommittee Chair, to transmit to NOP July 22, 2021. 

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