With summer drawing to a close, poinsettia production is on the horizon. Susceptible to a variety of insects and diseases, poinsettias require the use of proper cultural practices to help reduce pest pressures and help ensure healthy, salable crops. Be sure to protect against these common poinsettia threats:

Botrytis

Botrytis is particularly threatening during propagation and at the end of production when plants are ready to ship. Once established, gray mold can quickly spread throughout the crop and production area. Initial signs of infection appear as water-soaked spots on foliage. To help curb disease development:

• Provide a clean, dry growing environment
• Scout frequently, looking for symptoms such as small, light brown spots on flowers, v-shaped, tan-brown lesions on foliage and plant wilting
• Provide good plant spacing and horizontal air flow
• Keep humidity low by heating and venting

Pythium

In the late fall and winter when days are cloudier and the greenhouse temperatures are cooler, the growing media can remain wet longer. These are optimal conditions for oospores of Pythium spp. to germinate and invade wounds and tender plant tissue. When scouting for Pythium infections, look for stunted plants or lower stems with water-soaked tissue. In some cases, infected plants have light green or yellow foliage, with damaged roots that are brown and soft. Cultural tips to prevent infection include:

• Cleaning the benches and growing areas of debris and sanitizing between crops
• Elevating pots in low areas where water may pool
• Immediately removing diseased plants from the area to limit spread

Whiteflies

Whiteflies can be especially damaging to poinsettias as they insert their piercing, sucking mouthparts into the phloem to extract plant sap, which affects plant vigor. When scouting for whiteflies, check the undersides of leaves for nymphs and eggs. Additionally, look for signs of black sooty mold, which is the honeydew secreted from the insects. To prevent whiteflies from establishing in your operation:

• Maintain weed-free production areas. Whiteflies feed on numerous hosts, and weeds are potential sites of contamination
• Inspect new shipments of plants for mature whiteflies and nymphs
• Use screens in greenhouses to protect growing plants

Implementing proper cultural practices is the first step toward preventing insect and disease pressure in your operation. However, plant protection products are essential tools for enhanced protection when environmental conditions are conducive to pest development. Consider implementing a poinsettia agronomic program, such as this one from Syngenta, which provides a framework for rotating products with different strengths and modes of action while preventing the development of resistance.

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