The Poinsettia Playbook

Another vibrant poinsettia season is rolling in, promising a sea of colors. While advances in genetics and production techniques have helped increase quality and reduce costs, there’s a hidden villain lurking in the shadows. The silent saboteurs — pests and diseases — can shatter a perfect crop. Triumph over these unwanted guests at the early stage of the crop results in better grade and quality, all while keeping the costs down. Addressing pest management practices before and during propagation ensures your poinsettia crop starts off on the right foot.

Make a plan. For those of us who can take a breath between the mad dash of Mother’s Day and the start of the poinsettia season, these few days are precious for planning a proper crop production and pest management schedule. If you haven’t done that, it’s not too late. Take this opportunity to review what worked or didn’t last year and write out a production calendar. This plan will be crucial for every team member to understand and complete these time-sensitive tasks.

Have a clean start. Having a clean propagation area is just as important as having high quality cuttings. Bench surfaces should be cleared of media, mats, and debris from the previous crop. Bench surfaces and irrigation equipment should be sanitized thoroughly with a disinfectant. Weeds under the benches should be removed. These sanitation practices eliminate refuges that may shelter pests and pathogens.

Some of us produce our own cuttings from stock plants. Healthy stock plants produce high quality cuttings and, in turn, a successful crop. It is important to remember that stock plants also start with cuttings, so proper treatment of these foundation cuttings will set the stage for the rest of the production process. Whitefly, Lewis mite, botrytis, erwinia, and rhizoctonia on the stock plants will become problems for the rest of the crop. We should stay vigilant of any issue and start treatment as soon as a population or symptom is observed.

Because having pest-free stock plants is crucial to producing clean cuttings, I recommend a consistent scouting and management program to keep the problems at bay. Many insecticides, miticides, and fungicides provide excellent protection to poinsettia plants. Decree was highly effective in preventing botrytis blight on poinsettia in a study conducted by Dr. Mary Hausbeck of Michigan State University. In a study published by Gunn Gill and me, one drench of systemic insecticides, or two biweekly sprays of Rycar provided greater than 85% reduction in whitefly populations eight weeks after treatments. An insect growth regulator, such as Talus, is the cornerstone of a whitefly management program, particularly in operations where neonicotinoids can not be used. Talus has a unique mode of action and the ability to reduce nymph survival and adult fecundity, i.e., break the whitefly’s life cycle.

In addition to proper care after receiving, cuttings from an outside propagator should also be carefully inspected for pests and diseases and treated when necessary. Studies by Dr. Rose Buitenhuis of Vineland Research and Innovation Centre and by me demonstrated that pre-sticking dip of poinsettia cuttings in horticultural oil (0.1%), insecticidal soap (0.5%), and BotaniGard (label rate) is effective in cleaning the cuttings of whiteflies, thrips, and mites. Dip of cuttings from stock plants, even if the stock plants appear to be clean, will have the same benefit.

For those practicing biological control during the finishing stage and needing to manage pests and diseases on stock plants or cuttings, it's important to select pesticides with minimal impacts on biological control agents. Some of the insecticides, such as Rycar, Talus, oil, and biopesticides, applied on stock plants or during propagation, are known to have no impact on the survival and activity of parasitic wasps, predatory mites, and predatory beetles during finishing stage. Growers who source cuttings should find out from the propagators which insecticides had been used on the stock plants and how these insecticides may impact their biological control program.

Pest management during propagation. Fungus gnat, erwinia, botrytis, and rhizoctonia root and crown rot are the major issues during propagation. Whitefly, thrips, pythium, and poinsettia scab may also raise their ugly heads. Hopefully, sanitation has removed much of the inoculum and minimized the severity of these pests and diseases. The major pests and diseases during propagation have one thing in common—they benefit from a wet environment. Therefore, maintaining appropriate rooting media moisture level through proper irrigation, light and ventilation management goes a long way in reducing pest incidence and damage.

Fungus gnats love to feed on poinsettia roots, and on stems and leaves touching the media. Adults should be constantly monitored with yellow sticky cards, and the larvae can be monitored with a potato wedge placed in the media. The success of a fungus gnat management program rests with moisture management and treatment targeting larvae through drench or sprench of Ornazin and insect growth regulators (such as pyriproxyfen and cyromazine), or through releases of biological control agents (such as Bacillus thuringiensis subspecies israelensis, Steinernema feltiae, Stratiolaelaps scimitus (a.k.a. Hypoaspis miles), and Dalotia coriaria).

Copper-based fungicides, such as Camelot O and Junction, are effective in slowing the spread of erwinia. Decree is effective in preventing botrytis blight. The propagation stage is an excellent time to consider incorporating plant symbionts, such as Trichoderma species contained within Obtego, to enhance root growth and protect the plants from soil-borne diseases, such as root and crown rots caused by Rhizoctonia and Pythium. In a trial conducted by scientists at SePRO, rhizoctonia infection level on poinsettia plants that had received three drench applications with Obtego (at 5 oz. per 100 gallons) was 38% lower than inoculated control and 33% lower than RootShield Plus (at 5.5 oz per 100 gallons). The quality of Obtego-treated plants was 107% and 93% better than the inoculated control and RootShield Plus-treated plants, respectively.

A clean start, rigorous scouting, appropriate treatment of cuttings, and pest management during propagation are crucial aspects of a successful poinsettia growing season. Thorough planning, combined with proven pest and disease management practices, can protect your crop from lurking threats and secure its potential for stunning displays of color.

Juang Horng (J.C.) Chong, Ph.D is a Technical Development Manager, Ornamental at SePRO.