Only first instar larvae of Frankliniella occidentalis can acquire tomato spotted wilt tospovirus
It is generally admitted that only thrips larvae can acquire tomato spotted wilt tospovirus (EU annexes I/B and II/A2). Studies have been carried out in the Netherlands to define more precisely the developmental stages at which Frankliniella occidentalis (EPPO A2 quarantine pest) can acquire and transmit the virus. Results showed that only first instar larvae of F. occidentalis can acquire the virus after ingestion. Second instar larvae failed to acquire and maintain the virus, and did not became transmitters. After acquisition by first instar larvae followed by a latent period and virus replication, tomato spotted wilt tospovirus can be transmitted by second instar larvae and adults. The authors concluded that the current control measures against tomato spotted wilt tospovirus, which are mainly targeted against stages transmitting the virus, might be more effective if they were directed at the beginning of the transmission cycle (i.e. against the first instar larvae).
Sources
van de Wetering, F.; Goldbach, R.; Peters, D. (1996) Tomato spotted wilt tospovirus infection by first instar larvae of Frankliniella occidentalis is a prerequisite for transmission.