Impatiens necrotic spot and tomato spotted wilt virus spread easily throughout the United States because of the way plant material is transported. Roses and poinsettias are two of the few greenhouse plants that are not hosts of these diseases. Diagnosis often is misleading, if based on symptoms alone. Thrips are common transport vehicles for the viruses. Viruses cannot be controlled with pesticides, but instead must be controlled through other management practices.
Prevention is best.
Plant viruses, as a rule, are named after the first plant on which they are found. TSWV first was discovered on tomatoes in 1919 and now is known to infect over 300 different hosts. Previously, these viruses had been a problem in subtropical areas. It was not until the late 1980s that they began to affect the U.S. greenhouse industry. Because of the way plant material is transported, the viruses spread quickly across the United States and now are found everywhere.