Because of the way plant material is transported, the viruses spread quickly across the United States and now are found everywhere. Roses and poinsettias appear to be two of the few plants that do not play host to these diseases. The list of annual and perennial ornamental Crops affected by this virus is large. Necrotic spots, streaking, ring spots, stunting and wilting are some of the many symptoms exhibited by these viruses. Symptoms may resemble fungal and bacterial diseases or environmental stresses.
Diagnosis often is misleading, if it is based on symptoms alone.
All viruses are obligate parasites, which means they cannot survive outside of their host and must be moved from one plant to another by seed or Insects. This process is called vectoring. TSWV is carried only by certain species of thrips. At this time, INSV is known to be spread only by the western flower thrips. TSWV has been reported to be transmitted in the seed of Petunia x hybrida and Lycopersicon esculentum .