Authors: Joyce G. Latimer, Extension Specialist, Greenhouse Crops; Virginia Tech
Publication Number 430-102, November 2001
Table 1 Plant growth regulators used to reduce plant height during the production of floricultural crops.
| Trade name/Common Name | Application methods | Comments | Concerns |
|---|---|---|---|
| B-Nine daminozide Uniroyal Chemical Co. | Foliar spray Cutting dip | Apply uniformly to all foliage. NO soil activity. Effective on a broad list of species, but low level activity and short residual; multiple applications generally required. Increased activity when tank mixed with Cycocel. | Safe, few incidences of phytotoxicity or overstunting. Do not overhead irrigate within 12 hr after treatment. Use weight to measure new WSG formulation because the volume measured will be different from the old SP formulation. |
| Cycocel chlormequat chloride Olympic Horticultural Products | Foliar spray Drench | Standard for geraniums, poinsettias, and hibiscus; enhances flowering of geranium and hibiscus. Recent label change allows use on a broad spectrum of crops. Activity is low, multiple applications generally required. Increased activity when tank mixed with B-Nine. | Causes discoloration of leaves especially with rates above 1500 ppm; phytotoxicity reduced in tank mix with B-Nine. Less effective under high temperature conditions. |
| A-Rest ancymidol SePRO Chemical Co. | Foliar spray Bulb dip Drench Chemigation Injection | Broad spectrum label. Very active on bedding plants (except geraniums and impatiens); commonly used on plugs. Monderate activity. | Very safe. Relatively expensive for many crops, but used extensively on plugs. |
| Bonzi paclobutrazol Uniroyal Chemical Co. | Spray Media spray Drench Bulb dip Chemigation Subirrigation | Apply uniformly to cover stems (not absorbed by leaves). Much more active than above PGRs; measure accurately. Spray procedure and uniformity greatly affects results. Very soil active as a drench. | Spray volume critical to establishing rates due to drench effect of runoff. Use higher rates under high temperature conditions. Late applications can reduce flowering. Phytotoxicity includes overstunting and may cause black spots on annual Vinca. Avoid drift onto non-target plants. |
| Sumagic uniconazole Valent USA | Spray Media spray Drench Bulb dip | Same chemical class as Bonzi but 8 to 10 times more active. Apply uniformly to cover stems (not absorbed by leaves). Spray procedure and uniformity greatly affects results. Very soil active as a drench. | Spray volume critical to establishing rates due to drench effect of runoff. Use higher rates under high temperature conditions. Late applications can reduce flowering. Phytotoxicity includes overstunting. Avoid drift onto non-target plants. |
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