March 2015

Additional Studies from the North American Poinsettia Trials By Jim Barrett and John Dole

At North Carolina State University (NCSU) Emma Lookabaugh, graduate research assistant with the NC State Plant Disease and Insect Clinic, conducted a survey of North Carolina greenhouses, which revealed Pythium aphanidermatum to be the primary species associated with Pythium root rot of poinsettias. Symptoms of Pythium root rot include stunting, root necrosis, wilting, defoliation, poor vigor and, in extreme cases, death of the plant. For this study, 34 commercial poinsettia cultivars were evaluated for partial resistance to Pythium root rot caused by Pythium aphanidermatum.

Rooted cuttings of several DŸmmen and Ecke cultivars with a range of characteristics were grown in 6-inch pots and inoculated with Pythium aphanidermatum three weeks after transplanting. Plants were evaluated and scored for root rot ratings and plant health ratings approximately three months after transplanting. The hybrid cultivars 'Princettia Max White' and 'Luv U Pink' had the lowest amount of root rot. The six cultivars with the combined least root rot and highest health ratings were 'Premium Red', 'Princettia Max White', 'Luv U Pink', 'Infinity Red', 'Premier Red' and 'Jubilee Pink'. Several cultivars were able to withstand significant root necrosis with minor above-ground symptom expression as compared to non-inoculated controls. Among the lowest ranking cultivars, 'Sparkling Punch' had the most root rot followed by 'Enduring Red', 'Jubilee Red', 'Red Glitter' and 'Advent Red'.

NCSU Consumer Survey

At NCSU we conducted a survey of consumer preferences on 113 poinsettia cultivars during our annual consumer open house (see Table 1, page 16). We asked consumers to list their top three favorite red, white, pink and novelty poinsettias. We also asked for their overall favorite cultivars and poinsettia combinations. 'Dramatic Red' and 'Titan Red' were the top scoring red cultivars. 'Visions of Grandeur' was the favorite pink and 'Polar Bear' the favorite white. Not surprisingly 'Sonora White Glitter' and 'Ice Punch' were not only the top novelty cultivars but also the top overall favorites. Both cultivars routinely land in the top five cultivars each year of consumer testing. However, overall favorites in consumer testing should be taken with a grain of salt as sales data show that consumers prefer to buy the traditional reds. The highest ranked combination was Cortez Burgundy and White. Of the 185 surveys, 70 percent were completed by women and 30 percent by men and more than 60 percent were 60+ years old. Close to 50 percent of the survey takers purchased one to two plants per year, while 30 percent bought three or more per year.

UF Consumer Preferences

During the University of Florida (UF) student poinsettia sale, for the first time we allowed the consumers to purchase plants directly from the cultivar trial area. Then we watched to see which cultivars they purchased first. The plants picked the quickest were 'Princettia Max White' followed by 'Luv U Pink' (and two color sports) and 'Princettia Dark Pink'. Another new cultivar, 'Jingle Bell Rock' was selected quickly. These are all new selections that were described in the article on new cultivars in February GPN.

Whitefly Control Without a Neonicotinoid

For the UF cultivar trial an objective was to achieve whitefly control without the use of a neonicotinoid. Table 2 shows the rotation of chemicals that were used to successfully produce the crop. In Florida, adult insects are entering the greenhouse through October, so even if the crop is clean it is important to have good systemic insecticides in the plants during the second half of the crop when the heavy plant canopy makes sprays less effective.

UF Evaluation of Rycar on Poinsettias

Rycar is a new insecticide that has a novel mode of action and could be important in a rotation program for whitefly control. An issue for new products on poinsettias is the potential for phytotoxicity. To test the potential for problems, we applied Rycar once or twice at up to 4 times the recommended rate to plants soon after pinching and to plants with developing bracts. No injury was found with any of the sprays even at the very high rates.