This poinsettia has suffered from an invasion of whiteflies. Sometimes it's best to destroy heavily infested plants. Figure B Wrap both pot and soil with aluminun foil, and wash the undersides of the leaves to control insect pests.
Greenhouses provide plants the perfect indoor growing conditions.
Unfortunately, they can also be home to insect pests. To test for whitefly, tap a leaf gently. If a cloud of tiny white insects flies off and then resettles, you probably have a whitefly infestation. To get rid of them, hang yellow sticky traps near infected plants, spray with insecticidal soap according to label directions, and keep the greenhouse clean and free of fallen foliage. To check for spider mites, hold a piece of white paper under a leaf, and give the leaf a good tap.