Protecting Poinsettias with an Agronomic Program

Fall is quickly approaching, which means it is time to start gearing up for poinsettia production. Poinsettias are susceptible to a variety of diseases and pests, like Botrytis and whiteflies, so it is important to take preventive actions to ensure high-quality crops. 

Keep Whiteflies Away

Poinsettas in greenhouse​​​​​​​Poinsettias tend to attract whiteflies more than any other pests. Adult and immature whiteflies have piercing-sucking mouthparts that are inserted into the phloem and extract plant sap, which affects plant vigor. Nymphs cause most damage, including: 

    •    Reduced leaf expansion
    •    Chlorotic spots on the top sides of leaves
    •    Leaf discoloration or silvering
    •    Presence of honeydew secretions on leaves that can result in black sooty mold 

Whitefly populations can build quickly, so scouting on a weekly basis is essential. It is helpful to examine the undersides of leaves for larvae and nymphs with a hand lens. 

Gain Control of Common Diseases

The most common diseases poinsettia growers may encounter are: Alternaria leaf spots 

Alternaria leaf spots begin as small lesions with a tan center and dark margins. They are somewhat rounded and irregular in shape, and usually surrounded by a chlorotic tissue. They can be found on the lower leaves and can be mistaken for Xanthamonas sp. leaf spot. As the infection spreads, the leaf will become chlorotic and drop from the plant. 


Botrytis thrives in cool, humid environments and can be particularly problematic in the later part of poinsettia production. Initial infections cause water-soaked, V-shaped lesions on the foliage and bracts. Once established, the mold can quickly spread throughout the crop and production area. 

Powdery mildew

Powdery mildew can be a problem on poinsettias produced in cooler regions of the country. The fungi form white, talcum-like spots on leaves, stems and flowers. Over time, they increase in size and number to cover the plants’ surface, reducing growth and causing leaves to turn yellow, brown and then drop. 

Poinsettia Agronomic Program

Providing a clean, dry growing environment and checking incoming plants for symptoms are two steps to help prevent pests and disease. Mainspring® GNL insecticide, powered by a novel active ingredient in IRAC Group 28, is an excellent option for long-lasting control of whiteflies. Applying a broad-spectrum fungicide, such as Mural®, can help prevent ornamental diseases at any stage in production, from propagation to shipping. As an advanced generation SDHI, Mural has shown superior systemic control compared to strobilurin fungicides. This makes it an excellent choice for combatting diseases like Botrytis, leaf spots and powdery mildew.
If you are beginning from propagation or transplanting from liners, Syngenta has developed agronomic programs that provide recommendations to control and prevent multiple insects and diseases that can impact the quality of your crop. The application frequency should be based on the activity of the product, current environmental conditions, pest lifecycle and level of pressure. 

The following excerpt of the poinsettia agronomic program provides recommendations for the first seven weeks of production: 



Products (Rates per 100 gal)

Target Pests/Notes



Citation® 2.66 oz. (Drench)

Fungus gnats (if needed)


Avid® 8 fl. oz. + 

Mural 4-5 oz. (Spray)

Mites, Thrips, Whiteflies

Alternaria, Botrytis, Scab, Powdery mildew


Segway® 3 oz. + 

Medallion® WDG fungicides 1-2 oz. (Drench)

Pythium, Phytophthora, Rhizoctonia 

Root and Stem Rots


Endeavor® 5 oz. OR Rycar® insecticides 3 fl. oz. (Spray)


(Apply as needed to reduce adult pressure)



Daconil® Ultrex 1.4 lb. + 

1Dithane® 75DF 1.5 lb. (Spray)

Alternaria, Botrytis, Powdery mildew, Rhizoctonia, 2Scab


Protect new growth

Avid 8 fl. oz. + 

Mural 5-7 oz. (Spray)

Mites, Thrips, Whiteflies 

Alternaria, Botrytis, Powdery mildew, Scab


2-3 weeks after pinch

Mainspring GNL 8 fl. oz. (Drench)

Whiteflies (Bemisia sp.)


Subdue Maxx® 1 fl. oz. OR Heritage® fungicides 1 oz. (Drench)

Pythium, Phytophthora, Rhizoctonia

1Apply Dithane or other Mancozeb product for scab.

Download the program now.

All photos are either property of Syngenta or are used with permission. 

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