Toxic Effects of Plant Growth Regulators

The Complete Grape Growing System

The Complete Grape Growing System

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Details of the effects of some representative PGRs on various species, including humans, are given in Table 15.1. If properly used, PGRs have an excellent safety record. However, if the wrong concentration is used, if safety equipment is not properly used, or if the application times are not correct, poisoning can occur in plants, animals, and humans.

A good example is hydrogen cyanamide. This PGR is considered very effective and economical in assuring uniform bud break in crops including peaches, kiwis, and grapes. Uniform maturation of buds results in the uniform ripening of the fruit so that all the fruit on one tree can be harvested at


Chemical name

Common name

Trade name Target crop Action on plant Sentinel human effect


Chemical name

Common name

Trade name Target crop Action on plant Sentinel human effect

Chemical name:

A-Rest® controls the height

A-Rest® is a plant growth

• Acute toxicity (ancymidol)


of container-grown lilies,

regulator that reduces

Mouse: LD50 5000 mg/kg


poinsettias, chrysanthemums,

internode elongation

Rat, adult: LD50 4500 mg/kg

5-pyrimidine methanol)

dahlias, tulips, and foliage

Rat, newborn: LD50 3 50 mg/kg

and bedding plants;

Dog: LD50 > 500 mg/kg (emesis)

Common name(s):

effectively reduces internode

Monkey: LD50 > 500 mg/kg (emesis)


elongation, resulting in more

Chicken: LD50 > 500 mg/kg

(registered with EPA)

compact plants

For A-REST®, the oral LD50 in rates is

> 5 mL/kg

Trade name(s) and

• Subacute toxicity: all rats survived without


significant toxicity when fed 8000 ppm of ancymidol


for 3 months. Dogs given daily oral 200 mg/kg doses

Dow Elanco & Co.

of ancymidol for 3 months survived without

significant toxicity

Dermal toxicity and inhalation dangers: when

ancymidol and A-REST® at a concentration of

5 mg/L of air were applied to the back of rabbits,

subjects were unaffected

Chemical name:

Increases the number of

Synthetic cytokinin, which

• General toxicity to wildlife and fish: TLM


lateral branches developed

stimulates growth of dormant

- 96 hr - 52 mg/L (blue gill)


on chrysanthemums,

lateral buds in several

TLM - 24 hr - 3 mg/L (trout)


carnations, and roses

plant species

• Acute toxicity—LD50 926 mg/kg (mice),

1640 mg/kg (rats)

Common name(s):

• Subacute toxicity—NEL >

SD8339 (registered

10,000 ppm (mallard)

with EPA)

NEL > 4,640 ppm (bobwhite quail)

Trade name(s) and manufacturer(s): ACCEL®

Plant Growth Regulator, Abbott Laboratories

• Chronic toxicity—no teratogenic effect at 320 mg/kg in rabbits

• Dermal toxicity and inhalation dangers—no identified hazards at use concentrations

Chemical name:

Chemical control of axillary

There is no information on

• Acute toxicity to mammals


bud (sucker) growth after

the mechanism of action of



topping the floral portion

CGA-41065 in controlling the


Prime + 1.2E


of tobacco

growth and development of

Acute oral LD50

>5000 mg/kg

4400 mg/kg


tobacco suckers


Common name(s):

Interferes with cell division by

Acute dermal LD50

>2000 mg/kg

2010 mg/kg

CGA-41065M, PRIME+

binding to tubulin, preventing


tubulin from forming

Eye irritation


Corrosive on

Trade name(s) and

microtubules which are required





for proper spindle development

Primary skin



PRIME + 1.2E

and mitotic division




Chemical name: Gibberellic acid

Chemical name: Gibberellic acid

Common name(s): Gibberellic acid, GA3 (registered with EPA)

Trade name(s) and manufacturer(s): Berelex (ICI), observed Gib-Tabs (Microbial Resources), Gib-Sol (Microbial Resources), Pro-Gibb (Abbott), Pro-Gibb Plus (Abbott)

Improving fruit set of blueberries with insufficient pollination; used for better color, firmer fruit, larger fruit, and to prolong the harvest period of cherries; used to reduce cherry flowering and fruiting to minimize the competitive effect of early fruiting on tree development; for cluster loosening and elongation and berry size increase of grapes

GA3 is a growth promoter; it accelerates vegetative growth of shoot producing larger plants; mostly due to cell elongation but sometimes cell multiplication may be involved; induces flowering by breaking dormancy

Acute toxicity—oral administration of massive single doses of 1 g kg-1 produced no toxic symptoms in rats; mice - 15 g kg-1 no toxic symptoms

Subacute toxicity—dogs and rats have no ill effects from daily doses of 1 g kg-1 6 days per week for 90 days; one group of rats has been fed for 14 months, no toxic symptoms observed Chronic toxicity—no ill effect on rats fed 5 to 8 weeks with 5% GA3 in diet; no changes found in organs tissue; guinea pigs - no toxic signs fed with kale for 3 months, treated with 250 ppm.

Table 15.1. Plant growth regulators. (continued)


Chemical name

Common name

Trade name

Target crop

Action on plant

Sentinel human effect

Chemical name:

1.1-dimethyl-piperidinium chloride

Common name(s).

Mepiquat-chloride (registered with EPA)

Trade name(s) and manufacturer(s):

PIX-BAS 08300E by BASF Wyandotte Corp.

Systemic plant growth regulator for limiting undesired vegetative growth of the cotton plant; reduces growth, increases boll set; affects maturity, yield, boll rot

Decreases plant height, increases boll set and yield; inhibits all elongation and node formation and increases leaf mesophyll structure; possibly inhibits biosynthesis of gibberellin acid

• Acute oral toxicity—oral LD50 (rats) = 1420 mg/kg; no eye irritation

• Dermal toxicity and inhalation dangers—acute dermal LD50 (rats) is greater than 5000 mg/kg; inhalation toxicity (rats) no reaction after 4-hour exposure

Regulates the growth of various species of turf grasses and broadleaf vegetation by suppressing seed-head formation

Inhibition of growth and development of the meristematic regions of responsive plants

Chemical name: n-[2,4-dimethyl-5-

[[(trifluoromethyl)-sulfonyl] amino]phenyl]acetamide

Common name(s): Mefluidide (WSSA, ANSI) (registered with EPA)

Trade name(s) and manufacturer(s): EMBARK® 2-s PBI/Gordon Col.

Regulates the growth of various species of turf grasses and broadleaf vegetation by suppressing seed-head formation

Inhibition of growth and development of the meristematic regions of responsive plants

Acute toxicity

Mice oral LD50 1920 mg/kg Rats oral LD50 > 4000 mg/kg Rabbits > 4000 mg/kg dermal LD50 Subacute toxicity

Dogs 90-day feeding "no effect" at 1000 ppm in diet Rats 90-day feeding "no effect" at 6000 ppm in diet Chronic toxicity—in lifetime feeding studies with rats and mice no adverse effects related to ingestion of mefluidide at a dose level of 600 ppm in the diet were observed. Reproduction and pup survival were not affected by mefluidide up to 6000 ppm in the diet during a 18-month 3-generation study with rats

Chemical name: 1-naphthaleneacetic acid

Common name(s): NAA (registered with EPA)

Trade name(s) and manufacturer(s): NAA-800; Fruitone®; In Rootone® Rhone-Poulenc Ag Company Products Co., Inc.

Thin apples, olive and pear Auxin activity blossoms; control apple and pear preharvest drop; stimulate root formation

• Dermal toxicity and inhalation dangers—rabbits primary skin irritation study: no irritation to abraded and nonabraded skin; rats 4-hour acute aerosol inhalation LD50: > 8.5 mg/L air

• Acute toxicity (rats)—LD50 approximately 1000 mg/kg body weight

• Chronic toxicity—8-day dietary LC50 (bobwhite quail): acute LC50 estimated to be greater than 10,000 ppm; 8-day dietary LC50 (mallard duck): acute LC50 estimated to be greater than 10,000 ppm

• Dermal toxicity and inhalation dangers—

acute dermal toxicity (rabbits)—LD50 greater than 5.0 mg/kg body weight; not considered to have potential as a primary skin irritant; primary eye irritation (rabbits)—considered an eye irritant; acute inhalation toxicity (rats)—not considered toxic by the route of administration

Chemical name: ga4-(1a, 2ß,4aa,4bß,10ß)-2,4a-dihydroxy-1-methyl-8-methylene gibbane-1,10-dicarboxylic acid,1,4a-lactone

Spray gynoecious cucumbers to develop male flowers

Close similarity in growth regulating activity of GA3 but differs in its capability of influencing growth in some species in ways not achievable with gibberellic acid

• Acute toxicity—the acute oral LD50 of gibberellin A4, A7 is >500 mg/kg (for mice)

• Dermal toxicity and inhalation dangers—avoid use in poorly ventilated areas ga7-(1a, 2ß,4aa,4bß,10ß)-2, 4a-dihydroxy-1-methyl-8-methylene gibb-3-ene-1, 10-dicarboxylic acid,1, 4a-lactone

Compound Chemical name Common name Trade name

Target crop

Action on plant

Sentinel human effect

Common name(s): Mixture of GA4 + GA7 (registered with EPA)

Trade name(s) and manufacturer(s): Pro-Gibb 47, Abbott Labs Regulex, ICI Plant Protection

Chemical name(s): ba-6-benzylamino purine

Ga4-(1a, 2ß,4aa,4bß,10ß)-2, 4a-dihydroxy-1-methyl-8-methylene gibbane-1, 10-dicarboxylic acid,1, 4a-lactone

Increases red delicious apple size, weight

Gibberellin activity

Acute toxicity: the acute oral LD50 of N-(phenyl methyl)-1H-purine on mice is 1690 mg/kg, while for gibberellin A4,A7 it is greater than 500 mg/kg Dermal toxicity and inhalation dangers: promalin is nonirritating in dermal toxicity testing but does cause injury to the eye ga7-(1a, 2ß,4aa,4bß,10ß)-2, 4a-dihydroxy-1-methyl-8-methylene gibb-3-ene-1, 10-dicarboxylic acid,1, 4a-lactone

Common name(s): Mixture of BA + GA4 + GA (registered with EPA)

Trade name(s) and manufacturer(s): Promalin, Abbott Labs

Chemical name:

Apples: promoting fruit Releases ethylene in plant tissues

• Acute toxicity: rats—LD50 4229 mg/kg body weight


maturity and loosening fruit;

• Subacute toxicity: 8-day dietary LC50 (mallard


promoting uniform ripening

ducks) 196 LC50 greater than 10,000 ppm; static

Common name(s):

and coloring of red varieties

96-hour toxicity (blue-gill sunfish)—TL50 estimated

Ethephon (ANSI)

without loosening fruit;

to be about 311 ppm Static 96-hour toxicity

(registered with EPA)

increasing flower bud

(rainbow trout)—TL50 estimated to be about

development on young trees

357 ppm

Trade name(s) and

Cantaloupes: promoting

• Chronic toxicity: considered noncarcinogenic,


fruit abscission

nonmutagenic, nonteratogenic


Cherries: uniform ripening

• Dermal toxicity and inhalation dangers: acute

ETHREL®, Plant

and loosening fruit, increasing

dermal irritation (rabbits)—5730 mg/kg—a single

Regulator, ETHREL®

dormant fruit bud hardiness,

instillation of 0.1 ml of Ethrel into the eye showed

Pineapple Growth

and delaying spring bloom

corneal damage in the nonirrigated group at day

Regulator, PREP,

of sweet cherries in the

14 whereas the irrigated group had recovered; acute


Pacific Northwest.

inhalation toxicity (rats)—inhalation of 2 mg/L air

Plant Growth Regulator -

Cotton: accelerating uniform

caused signs of irritation during 1 hour exposure;

Rhone-Poulenc Ag Company

boll opening

all animals appeared normal during 14 days

Cucumbers and squash: modifying

following exposure

sex expression for seed production

Daffodils: use a drench for

shortening stems of forced bulbs.

Geraniums: to increase


Greenhouse roses: use for basal

bud stimulation

Peppers: early, uniform ripening

and coloring fruit

Compound Chemical name Common name

Trade name Target crop Action on plant Sentinel human effect

Tobacco: hastening "yellowing" of mature tobacco and reducing curing time Tomatoes: accelerating and concentrating fruit ripening Walnuts: loosening walnuts and improving full removal

Chemical name: Butanedioic acid mono (2,2-dimethylhydrazide) (formerly succinic acid-2,2-dimethylhydrazide)

Common name(s): Daminozide (ANSO, ISO, BSI); Former literature references include SADH, B995, B9, and aminozide. Note: Food uses will be canceled. Ornamental uses remain in effect.

Trade name(s): and manufacturer(s): ALAR-85, KYLAR-85, B-NINE-SP by Uniroyal Chemical

Used on fruit-bearing trees, peanuts, ornamentals, grapes, and tomatoes; daminozide has a wide range of effects, from retarding vegetative growth, to controlling harvest quality factors, increase red color in apples, to concentrating maturity

Plant growth regulant of unknown mechanism

• Acute toxicity: acute oral LD50 (rat): 8,400 mg/kg

• Subacute toxicity: in a 90-day feeding study with rats, technical-grade daminozide had no adverse effect when fed at 43,200 ppm in a daily diet

• Chronic toxicity: a 2-year feeding test with rats and dogs indicated that technical-grade daminozide had no adverse effect at 3000 ppm in the daily diet (highest rate tested); a three-generation reproduction and lactation study with rats fed 300 ppm technical-grade daminozide in the diet showed no significant effect on either fertility or reproductive capacity

• Dermal toxicity and inhalation dangers: Acute dermal LD50 (rabbit): > 5000 mg/kg Acute inhalation LC50 (rat): > 147 mg/L

• Symptoms of poisoning: no known symptoms

Chemical name: 2-chloroethyltrimethyl ammonium chloride

Pears and apples: promotion of fruit bud formation, and increasing yields: also allows young trees to bear sooner

Common name(s):

Chlormequat chloridef BSI) :

Azaleas: to produce early budded, compact symmetrical plants for use in commercial forcing of early blooming azaleas other names are CCC, chlorocholine chloride. El 38.555 (Registered with EPA)

Trade name(s) and manufacturer(s): CYCOCEL®

Plant Growth Régulant, American Cyanamid Company: HORMOCEL, All India Medical Corporation

Chemical name: Tree growth retardant

(±)-r*,r*)-P-[(4-chlorophenyl) methyl]-a-( 1,1 -dimethylethyl)-l/i-l,2,4-triazole-l-ethanol

Common name(s): Paclobutrazol (registered with EPA)

Trade name(s) and manufacturer(s): Clipper®' Tree Growth Regulator

Source: Data from Cutler and Schneider (2).

• Acute toxicity: LD50 oral: male albino rats 0.48-0.94 g/kg

• Subacute toxicity: repeated feeding to rats for

29 days at 500. 1000. and 2000 mg/kg; all animals had normal behavior and food intake and weight gain of the test rodents remained within normal limits

• Chronic toxicity: 12 months of feeding of rats at 500 and 1000 ppm gave no symptoms of poisoning, differences in mean body weight, appearance or behavior, no differences in various hematological and clinical chemical determinations, and no untimely deaths were observed; in 12-month feeding studies with dogs on a diet containing

300 ppm (calculated on dry weight), regular examination of animals showed no gross or microscopic pathology referable to the compound; determinations of acetyl-cholinesterase in erythrocytes and plasma made after 4, 8, and 12 months on test indicated that the compound had no effect on red blood cells or plasma

Inhibitor of gibberellin biosynthesis

• General toxicity to wildlife and fish: contains methanol and cannot be made nonpoisonous

• Symptoms of poisoning: same as methanol the same time. For many years hydrogen cyanamide was used as a medication for the treatment of alcoholism in humans (albeit in much smaller concentrations than is used on plants). The chemical causes an Antabuse reaction in people who consume alcohol, including nausea, vertigo, hypotension, and, in extreme cases, circulatory collapse and death. Therefore, people who mix and apply the chemical must wear full protective ensembles, used closed air supply cabs for the tractors, and never consume any alcohol in liquid form or as a perfume or after-shave. Care must be exercised to isolate the field until the reentry period has passed. Treatment is supportive (see Chapter 13) (3,4).

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  • tarja pakarinen
    Can i use technical grade Daminozide for agriculture purpose?
    4 years ago
  • kiara
    Is spray of pgr, S harmful in apple plants?
    1 year ago
  • milly
    Are tree growth regulators safe?
    12 months ago
  • gary
    Is tree growth regulator safe for trees?
    7 months ago
  • rosa
    What adverse effects does using pix ultra plant growth regulator have?
    6 months ago
  • aki
    Is plant growth regulators safe for animals?
    4 months ago

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