Prohexadione-calcium

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Chemical Identification | General Product Information | Physical & Safety Data

Chemical Identification

Common Name

中文通用名

调环酸钙

IUPAC

Calcium 3-oxido-5-oxo-4-propionyl-3-cyclohexenecarboxylate

CAS

3-hydroxy-5-oxo-4-(1-oxopropyl)-3-cyclohexene-1-carboxylic acid calcium salt

CAS No.

127277-53-6

Molecular Formula

C₁₀H₁₀CaO₅

Molecular Structure

General Product Information

Category

Plant growth regulators > Unclassified plant growth regulators

Activity

Plant growth regulator.
Prohexadione-calcium is primarily active by foliar uptake and is transported both acropetally and basipetally within the plant. It has no residual activity and is rainfast within 8 hours of application.

In field trials, prohexadione-calcium gave results better than or equal to commercial standards at very much lower rates.

In wheat, the optimum time for application is at GS 29-45. The optimum timing for application to rice is from two weeks before heading to heading. The product inhibits a late stage of gibberellin biosynthesis, dissimilar to triazole PGRs such as uniconazole. The mode of action appears to be due to competition with the natural co-substrate 2-oxoglutarate at the active site of hydroxylases and, in this respect, is similar to that of daminozide.

In orchards, prohexadione-calcium reduces canopy growth allowing more light to reach the fruit and thereby improving its quality. The product may be applied to the entire canopy or selected areas. Total rates of 2.5 kg/ha per season of Regalis may be used, with a 55 day pre-harvest interval. The suppression of vegetative growth typically lasts 2-5 weeks per application, with no effect on growth on the following year. The product also reduces susceptibility to fireblight (Erwinia amylovora) and apple scab (Venturia inaequalis) although it has no direct effect on the pathogen. Rademacher (2004) noted that prohexadione-Ca is now believed to trigger pathogen resistance by inducing the production of flavenoids with phytoalexin-like properties. In addition, the more open canopy of treated trees allows better penetration of pesticide sprays.

In citrus, pot experiments were conducted with prohexadione-Ca using an organosilicone adjuvant and adjusting spray solution pH. Up to 40% reduction in vegetative growth was achieved by three months after application by a double application of pH adjusted prohexadione-Ca with a four week interval.

CropUse

Crop uses:
Rice, wheat, barley, turf, apples, peanuts, ornamentals, grass seed

Apples	83-3300 g ai/ha
Rice	7.5-10 g ai/ha
Peanuts	250-500 g ai/ha
Cereals	50-100 g ai/ha

Premix

Type	AI concⁿ
Suspension concentrate (SC)	1.0% (w/v)
Water-dispersible granule (WG)	10% (w/w)
Dust	0.12% (w/w)

Suspension concentrate, water-dispersible granules. Premix Parters: anilofos; bensulfuron-methyl; bentazone; bromoxynil 2,4-D; butachlor; clomazone; 2,4-D; fentrazamide; MCPA; metsulfuron-methyl; molinate; pendimethalin; pyrazosulfuron-ethyl; quinclorac; thiobencarb; triclopyr.

Physical & Safety Data

Physical Properties

(Tech) Yellow powder with sweet smell. Melting point >360°C. Hardly soluble in organic solvents.

Toxicology

(Rat): Oral LD₅₀ >5000 mg/kg. Inhalation LC₅₀>4.21 mg/l. Dermal LD₅₀>2000 mg/kg.
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Environmental Profile

Fish: LC₅₀ >150 ppm (carp), >100 ppm (rainbow trout). Bird: Oral LD₅₀>2000 mg/kg (bobwhite quail); Dietary Oral LC₅₀ >5200 mg/kg (mallard duck). Bee: Topical LD₅₀>100 μg/bee (honeybee).
WATER SOLUBILITY: 174.2 mg/l at 20°C.

Virginia quail	LD₅₀ >2,000 mg/kg
Rainbow trout	LC₅₀ >100 mg/litre
Bluegill sunfish	LC₅₀ >100 mg/litre
Carp	LC₅₀ >150 mg/litre
Earthworms _{[14 days]}	LC₅₀ >1,000 mg/kg soil
Bee _[contact]	>100 μg/bee

Fate in soil:
Aerobic soil metabolism is the principal route of degradation; laboratory studies indicated a half-life for parent prohexadione-calcium of 9.8 days. The major degradate at 30 days is carbon dioxide (79.8% of applied radioactivity). The adsorbtion Koc values in sand, clay, sterile loamy sand and loamy soils were 173, 155, 1428 and 421 respectively. Field soil metabolism studies in Texas, North Carolina, Oregon, New York and California resulted in half-lives of 0.8, 1.0, 5.7, 15 and 20 days respectively with the longer half-lives attributed to dry soils. Prohexadione-calcium is rapidly degraded photochemically in the soil. It has a half-life of between one and four days. The parent compound showed moderate to very high mobility in four soils in laboratory column leaching studies. However, the Koc values, rapid degradation in soil and the foliar application suggest that the product will have little adverse effect on groundwater supplies when used as recommended on the label. This conclusion was corroborated by environmental modelling studies.

Fate in aquatic systems:
Prohexadione-calcium is rapidly degraded by photolysis in water with a half-life of 9.9 days at pH 5, and 23.2 days at pH 9. Aqueous hydrolysis is also pH dependent; half-life is 4.4 days at pH 5, 65 days at pH 7 and stable at pH 9.

Transport Information

Signal Word:CAUTION; Hazard Class:III (Slightly hazardous)