E-Letter 4

As poinsettia crops finish we are hearing from growers about the following issues:

Height control of the crop is still an issue, but the needs are not consistent. Growers report that plants have been either too tall or too short. For those growers who have plants that are too tall, Bonzi drenches are being applied to help control late stretch. Growers still need to use care in application rates and volumes applied per pot to avoid causing problems with bract size.

For those with short plants use of positive DIF, and in warmer regions additional ammonium nitrate based fertilizer applications have been helpful. Some growers are experimenting with GA3 (ProGibb), although the details for this application are still under evaluation. We are not advocating this practice until growers have become familiar with the results and proper use. We will have more information on this treatment after this season and will report based on what growers experiences are.

Heat delay has been one factor in height of plants and is impacting the timing of crops. Temperatures (warm day and night) around most of the country in late September caused delays of between 7-14 days on many cultivars. Freedom has been fairly tolerant of this problem, although we are seeing some delay even on this cultivar. Mid season poinsettias like Prestige and Max Red are running about 1 week behind schedule and should be ready early December. In some areas the problem is further complicated by cloudy weather conditions during October. To help advance color development now, growers should provide as much light as possible (minimal shade on roof), warm night temperatures (68-70 F) and day temperatures that stay above 70 F on cloudy days and above 75 F on sunny days. Mid season cultivars that are still developing can not tolerate cooler day/night temperatures used to help tone the early blooming crops without further delays. Also, keep the plants a bit dry to help force color. Be cautious of this practice if fertilizer salts are elevated or if temperatures in the greenhouse will raise to 85 F or above. Be sure plants are provided adequate space and air circulation to help maximize drying of the soil and provide good light penetration to all parts of the plant canopy to help prevent stretch and any yellowing of lower foliage.

Reports of whitefly problems are limited but still present. The strong fall temperatures have limited any knock down from cold temperatures, allowing outside populations to continue to enter greenhouses and cause problems on the crop. Late pesticide treatments should be done with extreme care to avoid residue or burn that will reduce the value of plants. If making a late treatment using any wettable powder formulations, consider the addition of Capsil at low dosage (2-3 ounce per 100 gallons) to help minimize residue. Check the label closely to be sure the insecticide or fungicide being used should not be combined with an adjuvant before treating the crop!

Disease issues have been mostly limited to root rot (Pythium) and Botrytis. Powdery Mildew has only been reported in a few greenhouses and seems to be under good control this season. In all cases, growers need to continue scouting for potential problems and respond to any problems found in a timely manner. Keep in mind that organisms like Botrytis can be controlled effectively with good culture by keeping foliage and bracts dry. Root rot diseases are most likely to occur where damage from high fertility is a problem, or where plants are kept too wet. Preventive treatments for all of these diseases can be beneficial, however as bracts mature and the crop becomes more sensitive to damage growers must take caution in making any applications. Apply chemicals after the greenhouses have warmed up in the morning and plants can be treated without risk of staying wet for an extended time frame. Do not treat at the end of the day as the moisture that results from these treatments will promote development of diseases in the greenhouse.

This is a good time to look at poinsettia open houses held around the country to evaluate new cultivars for future production. We are excited about the overall performance of the new Prestige, Max Red and Enduring Pink. However, it is important that growers view these crops and consider the regional performance when making decisions on what to grow each year.

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