It is hard to believe that growers are amid another poinsettia season. After months of planning, cuttings are stuck and by the time you receive this newsletter, pinching will be completed. The race to control whitefly, to monitor plants for rot diseases and to assure that your plants are properly fertilized to avoid nutritional deficiencies or overfertilization is in full swing. 

In this issue, we are providing two articles on poinsettia nutrition – one on basic nutrition practices and one on an effective nutrient program to avoid poinsettia bract edge burn. I remember when bract edge burn first affected poinsettias. Growers would box plants and ship them to retailers. Well, in the 3 – 4-day shipping process, the bracts were destroyed by Botrytis. One mid-western U.S. grower lost three semi-truck loads of poinsettias to this horrible disorder in two weeks. But, as you will see in the article by Brian Whipker, the real cause is calcium deficiency with Botrytis as a secondary infection. The pleas for help were load and clear – please find a resolution to this problem. 

Fortunately, with the support of the American Floral Endowment, nutrient programs were modified to drastically reduce or eliminate the damage from bract edge burn. Read these two articles carefully and consider the recommendations as a positive, low costs insurance policy.

Also, you may be aware that many industry members are supporting a 5-year research program on thrips and Botrytis. These are difficult problems for the industry – plants and flowers are lost due to resistance to insecticides and pesticides, cultural programs and environmental conditions. We have asked the researchers at the University of Vermont to explain why thrips are so difficult to control. The University of Vermont is one of 7 universities that AFE is funding to identify innovative cultural and environmental programs to manage and control these pests. 

We welcome your comments about the issues your business is facing so future research is focused on critical industry problems and technology. AFE welcomes your support of research, scholarship and internship programs. 

Originally published in Greenhouse Grower

Pythium is a soil mold that is well known among greenhouse growers. This pest is not new nor one of the dreaded “invasive” pests that we seem to hear more about these days. Perhaps we’ve even grown a bit too comfortable with this pest and have become a bit lax in the needed preventive measures. After all, Pythium is just a root “nibbler.” How much damage can it really cause? On poinsettias, lack of vigor, uneven growth, and even stunted plants can result from a Pythium invasion. When the cultural aspects of the crop are a bit off-balance, such as high salts, the negative effects of Pythium can become magnified resulting in plant death. Overwatering the crop will also tip the balance in favor of Pythium root rot. Pythium’s nickname isn’t “water mold” for nothing!

Poinsettias require medium to high fertility levels between 150 and 300 ppm N, with the rate adjusted to take into account plant vigor. Optimal substrate pH values for poinsettia range from 5.5 to 6.5. If the substrate pH drifts lower than 5.5, plants will become stunted and color delayed. Substrate pH values above 6.5 inhibit Fe availability and induce interveinal chlorosis and stunted plant growth.

Poinsettias should be grown with a substrate pH range of 5.5 to 6.5. Use recommended 1:2 Extraction, SME, or PourThru methods to determine and monitor substrate pH and soluble salts [referred to as electrical conductivity (EC)] values. Additionally, conduct routine foliar analysis tests to monitor crop nutrient status. Tissue nutrient levels found in healthy, newly expanded poinsettia leaves and critical tissue values are provided in Table 1, which can help in diagnosing suspected nutrient...

Calcium is the primary element used for building cell walls. When calcium is low, marginal leaf or bract necrosis can occur. This can occur because calcium is taken up by the plant along with the water supply, mainly through evapotranspiration. So any environmental condition which limits water uptake and water loss through the leaf can create deficiencies.

Symptoms Calcium deficiency problems can appear on both the leaves and bracts. In the case of leaves, one will observe symptoms on the younger leaves that are completing their final 50% of expansion (Fig. 1). This occurs because young leaves require a tremendous amount of calcium in order to grow and create new...

In 2017, a special research campaign was established to address the control and management of Botrytis and thrips.

We have surpassed the goal to raise $1.5 million through industry support to conduct new and innovative research leading to effective control procedures and management strategies. But, we won't stop there! The research will lead to reduced losses and higher quality flowers and plants.

More than 23 organizations have already signed up to support this initiative. Find out how to join them to receive reports exclusively for supporters of AFE's special research fund!