Small, white insects flutter about my poinsettia when I water the plant. What are they and how do I control them?

FAQ
Question: 

Small, white insects flutter about my poinsettia when I water the plant. What are they and how do I control them?

Answer: 

The small, white insects are likely whiteflies.  Whiteflies are common insect pests of poinsettia, hibiscus, chrysanthemum, and a number of other indoor plants.  They are most often noticed when watering or handling a plant.  When disturbed, whiteflies flutter about the plant for a short time before returning to the plant.  

Whitefly adults are small, white, moth-like insects.  Female adults lay eggs on the undersides of the plant’s foliage.  After 5 to 7 days, the eggs hatch into small, pale green, immature insects called nymphs.  The nymphs crawl a short distance before settling down to feed for 2 to 3 weeks.  After feeding for 2 to 3 weeks, the nymphs progress to a nonfeeding stage and then finally to the adult stage.  

The nymph and adult stages of whiteflies feed by inserting their short, needle-like beaks into foliage and sucking out plant sap.  Heavy whitefly infestations may cause stunting or yellowing of leaves, leaf drop, and a decline in plant health.  

Whiteflies on poinsettias and other indoor plants are extremely difficult to control.  Prevention is the best management strategy.  When purchasing plants, carefully check for whiteflies and other insects.  Avoid purchasing insect-infested plants.  Insecticides are not a good control option as they are not very effective.  It’s often best to tolerate the presence of a small infestation of whiteflies on a poinsettia and then promptly discard the plant after the holidays.