Host Preference of Greenhouse Whitefly: Effect of Poinsettia Cultivars1

Abstract

Sixty-eight poinsettia cultivars ( Euphorbia pulcherrima Willd.) were exposed to a population of greenhouse whitefly ( Trialeurodes vaporariorum Westw.) for 9 weeks. Evaluation was based on 6 degrees of infestation by immature stages of whitefly on the bracts and upper and lower foliage. The upper foliage showed the heaviest infestation and was considered to be the best indicator of relative susceptibility. White bracts were more heavily infested than red bracts, while pink bracts were intermediate. A wide range in degree of whitefly infestation was found among poinsettia cultivars. Certain cultivars tested for 2 years showed appreciable resistance to infestation (‘U.S.D.A. 68-82-1’, ‘U.S.D.A. 68-160-2’, ‘Annette Hegg Maxi’, ‘Red Baron’, ‘Rudolph’).