Botrytis on poinsettias has been diagnosed on samples sent to the Plant and Pest Diagnostic Clinic and during visits to growers by Extension personnel. The first step in Botrytis control is to reduce relative humidity by coupling appropriate heating with adequate venting. In addition, Phyton 27 is a fungicide that can be applied if poinsettias have developed colored bracts. Dr. Nameth reports that INSV is showing up on New Guinea and other stock plants.
Watch out for powdery mildew on poinsettias! Powdery mildew on poinsettias was diagnosed in two separate greenhouse operations in Michigan. Prompt action eliminated the problem. This disease tends to appear at this time of the year. Look for symptoms on older leaves first. This problem can be taken care with Cleary's 3336, Terragard, or Strike. (Read labels before use!).
Pinpoint 15G can cause leaf burn on several ornamental plants at current recommended rates. Growers should run tests on several trial plants at several rates. Dr. Lindquist suggests that one-eighth teaspoon might be a better rate. Pinpoint 15G is Acephate, a systemic insecticide effective against a wide range of chewing and sucking pests.
"My poinsettias have colored bracts. What can I use to control whiteflies now?" This question is asked every year by some growers. Smoke generators of Plantfume 103 or Dithio can be used. Growers should be sure that the leaves and bracts are free of moisture droplets when using these products or spotting will occur. Plantfume 103 or Dithio is known as Sulfotepp, a short-residual, vapor active material that is applied as a smoke to kill aphids, whitefly and other small flying insects.
Improve post-production quality of your poinsettias. Late in production, keep medium nutrient concentration low. A standard practice is to stop fertilizing the last two weeks of the crop. However, if the crop has been grown at low to moderate fertility levels, do not eliminate fertilization. Instead, keep applying low fertilizer levels.
Piketon Research Center will conduct a Bedding Plant Workshop on December 6, 1996 for the new and/or small grower that has 1-3 houses. For more info. call 614-289-2071.
The Franklin Park Conservatory (Columbus, OH) poinsettia show runs November 30 until January 6, 1996. Standard admission is $5.00. For more info. call 614-645-5950.
Interested growers should note that various State pesticide recertification schools that cover greenhouse and interiorscape will be held November 26 in Cleveland, December 17 in Dayton, January 16 in Perrysburg and January 28 in Columbus. All commercial people will be notified with details or call your local extension office.
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