Studies on the transmission of European wheat striate mosaic virus by Delphacodes pellucida Fabricius

Several races of Delphacodes pellucida have been isolated that transmit European wheat striate mosaic virus with varying degrees of efficiency. The length of the incubation period of the virus in the vectors increased as the proportion of planthoppers that were able to transmit infection decreased.

Efficient races of D. pellucida transmitted virus to a high proportion of their progeny, but nymphs of inefficient races inherited little or no virus, even from infective mothers.

Congenitally infective inbred lines of planthoppers did not become more infective after feeding on infected plants, but planthoppers that did not inherit1 virus could usually acquire it with about the same efficiency as that of the parent race. Females of an efficient race that became infective as a result of feeding on infected plants as nymphs, 15 days before mating, transmitted virus to eggs laid from 10 to 15 days after mating, but females fed on infected plants only during mating usually did not transmit to their progeny, though they were able to infect plants within 15 days of acquiring virus.

Infective mothers that fed on infected plants as nymphs had 40% fewer progeny than did those fed on healthy plants. Some embryos died in the egg at a comparatively late stage of development, and it is probable that the virus was pathogenic to them. The poor reproductive ability of infective females tends to eliminate the virus from colonies that are unable to renew their infectivity by feeding on infected plants.