Myron K. Sellers
Central Region Horticulture
Poinsettias will soon be ready to sell. Now is the time to solve any last
minute problems with your plants. The cloudy weather we've been having
creates the perfect environment for botrytis on poinsettias with color.
Exo-Therm Termil is a smoke applied fungicide that is normally used in
commercial greenhouses to keep poinsettia bracts free of botrytis. It
should be applied every week until plants are out the door.
I've seen some poinsettias that still have whiteflies. I think in most
cases the Marathon was applied too early. Don't apply granular Marathon
until the plants have a good root system; that will be about two to three
weeks after planting. If you have whitefly problems now, Distance (a very
expensive IGR) and a Marathon WP may clear up the problem. Merit 75WP is a
form of marathon that is labeled for poinsettias in interiorscapes and can
be used for commercial grounds maintenance. I don't think it is labeled
for greenhouse use.
If your think your poinsettias are going to finish too tall, Bonzi can be
used as a drench to stop the plants from stretching. Don't use it as a
spray on the bracts. Bonzi used this late as a drench has little effect on
the size of the bracts, but if sprayed on the bracts, your blooms will be