Tips For Poinsettia Production
Use this advice on fertilization, and insect, disease and height control on poinsettias.
July 24, 2012
Potting: Immediately after planting, drench with a broad spectrum tank mix of Subdue Maxx at 1 oz/100 gal (or Truban WP at 8 oz/100 gal) + Medallion at 1 oz/100 gal (or Cleary’s 3336 WP). Also consider using broad-spectrum combination products such as Hurricane or Banrot.
Media: pH: 5.6 to 6.0 (measured in a saturated slurry). Use a peat-based media such as Fafard 2 Mix or 1P Mix or a bark-based media such as Fafard 4P Mix or 3B Mix.
Fertilization: Depending on light level, age and growth rate, constant feed with 225 to 250 ppm nitrogen for dark-leaf varieties and 250 to 275 ppm nitrogen for medium-green-leaf varieties is recommended. Feeding with low nitrogen at 100 tp 150 ppm nitrogen works well as long as all other nutrients (especially potassium, calcium, magnesium and micro-nutrients) at a high level.
Make sure to run trials first before using this strategy on the whole crop. In the beginning, up to 30 percent of the total nitrogen should be ammonium for optimum leaf expansion. If plants look strong with good leaf expansion, reduce ammonium to 15 percent by the end of September. If needed, rinse leaves lightly with plain tap water after irrigation to prevent fertilizer burn or leaf distortion on the young foliage.
For softer, lush growth, use 20-10-20 or similar high ammonium and high phosphorus fertilizers until October 1st, then alternate with high nitrate feeds such as 14-0-14, 13-2-13 or 15-0-15 until November 1st. Afterwards, use strictly 14-0-14, 13-2-13 or 15-0-15 until shipping. For more toned growth early in the crop use 17-5-17, 15-5-15 or similar calcium-magnesium nitrate (Cal-Mag) type fertilizers. Molybdenum and magnesium usually have to be added to the fertility program — if not already supplied in higher amounts with the other regular fertilizers. Drench plants with magnesium sulfate at 1 to 2 lbs/100 gal when early stages of magnesium deficiency are observed. Add molybdenum to fertilizers as supplemental ammonium molybdate or sodium molybdate.
To catch potential problems early on, a complete media analysis should be done prior to planting and every two weeks thereafter. Keep the soluble salt level at 1.5 mS/cm (in a saturated media extract, SME) for the first few weeks. Afterwards maintain 2.0 to 2.5 mS/cm for medium-green varieties and 1.5 to 2.0 mS/cm for dark-leaf varieties. After November 10th, steadily reduce fertilization to about 25 percent of the original strength. Two strong clear-water leaches should be done just before shipping to reduce bract-edge burn and root rot at the consumer level.
Temperature: 68° to 73°F during the day and 66° to 68°F at night is recommended until two to three weeks prior to shipping. Towards the end of the crop, slowly drop temperatures down to 65°F during the day and 65°F at night for medium-green-leaf and 62° to 63°F night for most dark-leaf varieties.
Cold Growing/Finishing: Syngenta Flowers conducted extensive trials across North America with many varieties to better understand the effects of cold growing/finishing on growth and flowering. For more information on cool growing and finishing, review the Energy Efficient Poinsettia Production document under Technical Support (click on Cultural Info) at SyngentaFlowersInc.com.
Light: Light levels should be at 3,500 to 4,500 foot candles (15 to 19 mols/day) until the middle of October and at about 3,000 foot candles (13 mols/day) until three weeks before shipping, then at 2,000 to 2,500 foot candles (10 to 11 mols/day) for the last two weeks of the crop.
Consistency of Bract Color: Providing even heat distribution and moisture levels along with good air flow yields the most consistent bract colors. Ensure plants have a good root system and avoid excess salt levels in the media. Eliminate nighttime light pollution (if you can read a newspaper, then there’s too much light). Watch for shaded areas in the greenhouse (e.g., gutters and shade curtains).
The use of a graphical tracking system is highly recommended. With similar day and night temperature setpoints, the need for chemical height control is minimal for many varieties. When day temperatures are more than 5°F higher than night temperatures, a Cycocel spray at 750 to 1,000 ppm, one to four times after pinching, is sufficient in Northern climates to control stem extension. When day temperatures are greater than 80°F and night temperatures greater than 70°F, spray a tank mix of Cycocel at 1,000 ppm plus B-Nine at 1,500 ppm one to three times, one to four weeks after pinching. Bonzi sprays can also be used at 5 to 10 ppm under these warm growing conditions. Proper growth regulation before and after the pinch, combined with high light conditions are critical to avoid early internode stretch and to “build” a sturdy plant. Avoid B-Nine and Bonzi sprays after flower initiation.
Florel: Florel plant growth regulator applied at 500 ppm three to five days before and five to seven days after pinching leads to shorter internodes, more even branching, reduced stem breakage and a rounder finished plant. For optimum results, add CapSil, moisten media, treat early in the morning and check for a good root system.
Mid-season Ultra-low-rate Bonzi Drench: Low-rate Bonzi drenches provide additional growth control without delaying color, distorting bracts or significantly reducing the bract size. The recommended drench rate after flower initiation and prior to 50 percent color is 0.05 (1/20) to 0.1 (1/10) ppm. For traditional late-season growth control, drench with Bonzi in the north at ¼ to ½ ppm (0.75-1.5 oz/100 gal) and in the south at ½ to 1 ppm (1.5-3 oz/100 gal). This can be done when the plants are about ½ to 1 inch below the desired height and/or one to two weeks (up to three weeks in the south) before shipping.
Gibberellic Acid (GA): For a moderate increase of internode length, spray GA at 2 to 3 ppm using ProGibb 4 percent (4 ml/10 gal) or Fascination, ideally in the first part of October. The maximum elongation occurs about 1 to 2 weeks after application. Two to four inches of growth are possible within that time frame, depending on variety and temperature. Spraying Fascination at 2 to 3 ppm with CapSil about two weeks before finishing improves the color of white varieties and can be used to increase bract size if needed.
Pythium: Apply Subdue Maxx at 1 oz/100 gal as a soil drench after planting. Rotate with Truban WP (6 to 8 oz/100 gal) or Segway (3 oz/100 gal) fungicides every four weeks for protection.
Botrytis: Maintain good air movement and low humidity. To avoid Botrytis, apply preventative fungicide sprays of Daconil ULTREX, alternated with Palladium (4 to 6 oz/100 gal), Heritage (4 oz./100 gal), Chipco 26019 or Decree (1lb/100 gal) after sticking and 7 to 10 days later.
Powdery Mildew: To prevent outbreaks, maintain good air movement and low humidity in the production area. Apply preventive fungicide treatments throughout the month of October if a history of powdery mildew exists. Effective fungicide spray treatments include Heritage (4 oz/100 gal), Palladium (4-6 oz/100 gal) and several products from FRAC group 3: Eagle 20EW (8oz/100 gal), Terraguard (8 oz/100 gal) and Strike 50 WDG (0.5 fl oz/100 gal).
Rhizoctonia: To prevent root and stem infections by Rhizoctonia spp., avoid planting too deeply and maintain proper EC levels and moisture content of the media. Drench with Heritage (0.9 oz/100 gal), Medallion (1 oz/100 gal) or a thiophanate-methyl product (e.g, Cleary’s 3336 WP or OHP 6672) at full label rate, alternating on a 4-week interval for prevention.
Whiteflies: To keep whitefly populations under control, drench the growing media with a neonicotinoid (MOA Group 4a) insecticide (e.g. Flagship) three to four weeks after planting (or after pinch). Before the neonicotinoid soil application, Avid, Endeavor, Scimitar GC, Talstar, Sanmite, Distance, limited number of products and Judo insecticides are among those products labeled for whitefly management. If late-season control is needed, spray with Avid, Flagship, Talus or Tristar (only if a Group 4A was not drenched) insecticides using a spray adjuvant like CapSil.
Thrips: Avid, Botanigard, Conserve, Mesurol, Tame/Orthene tank mix (or total release aerosol) and Overture insecticides are some of the products used successfully for thrips management. After bracts form, use Avid or Conserve.
Fungus Gnats & Shore Flies: Good sanitation procedures are still the first line of defense for controlling fungus gnats and shore flies. Options for controlling fungus gnat larvae include: Azatin XL, Citation, Distance, Duraguard ME, Gnatrol insecticides or beneficial nematode (Steinrnema feltiae) products, such as Nemashield, Nemasys and Exhibitline SF.
Karl Trellinger is a Technical Services Specialist with Syngenta Flowers, Inc. He can be reached at firstname.lastname@example.org
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