Though growing Poinsettias can be challenging, it’s hard to argue they’re not worth the trouble: Poinsettias make up one of the most reliable niche markets in the industry. They are one of just a few greenhouse crops consistently sold in the final months of the year and account for the lion’s share of sales.
One of the keys to succeeding in this market is to deliver a healthy, vigorous, disease-free crop to your customers. This is easier said than done; Poinsettias are susceptible to many different diseases and problems over the course of their long growing season. This article will help you learn to identify and respond to four diseases that tend to strike early in the production cycle: Erwinia, Xanthomonas, Scab, and Botrytis. A brief description of each disease follows, along with a chart to give you at-a-glance guidance in managing these diseases.
Since many diseases present similar symptoms, it’s always important to obtain an accurate diagnosis from a laboratory. If one or more of the above diseases strikes, Phyton 27 and Phyton 35 can be used at the curative rates—along with the appropriate cultural controls—to help your crops win the battle. See the Grower Talks article listed below for one grower’s story on how he conquered a Xanthomonas infection.
For best results, regularly rotate fungicides and bactericides to combat resistance. Phyton 27 and Phyton 35 are excellent resistance management/rotation partners and have a low risk of phytotoxicity when used as directed.
Use the table below as a handy reference for identifying and managing these diseases.
|Pathogen||Symptoms||Prevention and Control|
|Erwinia Blight (caused by Erwinia Carotovora)||Plants wilt, yellow and collapse. Stems develop a mushy consistency. Cuttings turn brown and die. Wounded tissue susceptible, disease usually starts at the base of the cutting. Plants may have a fishy odor. Can be mistaken for Rhizoctonia; accurate diagnosis is important.||
|Xanthomonas (caused by Xanthomonas campestris)||Water-soaked, gray pinpoint spots, usually most severe on lower leaves. Spots turn yellow to tan and develop into an angular shape. Spots tend to be 1/8” wide with irregularly raised edges, often surrounded by a yellow halo. Can be confused with Scab; an accurate diagnosis is essential.||
|Scab (caused by Sphaceloma poinsettiae)||Slightly raised, circular or elongated lesions on the stems and petioles. These lesions are tan in the center and often surrounded by white, red, or purple margins. Affected leaves may become distorted, and may yellow and drop. In advanced stages, the stems will grow very tall while the leaves will remain small.||
|Botrytis Blight (caused by Botrytis cinerea)||Fuzzy gray sporulation. Brown spots on flowers, leaves, or stems.||
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