Often a sign of a large whitefly population directly feeding on the poinsettia crop is chlorotic and bleached stems, leaves and bracts. In order to prevent this from occurring, growers should maintain good sanitation, install and monitor yellow sticky cards and routinely inspect the underside of leaves for the presence of whitefly eggs, nymph and adults. If whiteflies are found implement integrated pest management (IPM) practices to avoid the above problems and prevent whitefly pesticide resistance.
Chlorotic and bleached stems, leaves and bracts are often signs of heavy whitefly pressure on poinsettias.
Information from the Purdue Plant and Pest Diagnostic Laboratory Website http://www.ppdl.purdue.edu/PPDL/weeklypics/10-29-07.html