The lack of diagnostic symptoms has driven efforts to develop specific confirmatory tests that can be easily performed by growers or in diagnostic laboratories as a first step in control. Less than ten species of thrips have been confirmed as vectors of Tospoviruses and specificity between thrips and tospovirus species has been shown. Tospoviruses replicate in their thrips vectors, thus the insects not only spread the virus, but serve as a virus host. Click the image for a larger view. When larvae feed on infected plants, ingested virus crosses the midgut barrier and enters the salivary glands.
Transmission then occurs when the virus moves into the plant with the saliva during feeding.
A midgut barrier in adults prevents virus ingested during this stage from moving to the salivary gland. While the insects remain infective for life, there is no evidence of transovarial passage from one generation of thrips to the next. Seed transmission of Tospoviruses is not known to occur, but some of these viruses are commonly spread in infected propagation material when crops are vegetatively propagated. Control Control of Tospoviruses remains problematic. Cultural practices and varietal selection have proven effective in minimizing losses due to TSWV in some field crops.