X-disease Vector Identification and Acquisition From Low
Author: Tobin Northfield
Published: 2024
Summary: A large part of X-disease management has been focused on controlling X-disease vectors. In the 1950s in Wenatchee, WA Homer Wolfe tested the vector capacity of 200 species of leafhoppers before identifying Colladonus geminatus as the key vector in Washington, and later Colladonus montanus reductus was identified as a key vector in California. However, given the time that has past since that research, it is important to search again for unknown vectors. In our survey of 22 (in 2021) and 30 (in 2022) sites throughout the Washington cherry growing region, the vast majority of leafhoppers were not Colladonus spp. leafhoppers. However, we found no evidence of any unknown vectors transmitting X-disease phytoplasma. Previous research has demonstrated that Euscelidius variegatus can transmit X-disease in the laboratory, but with a longer latency period than Colladonus species. Here we tested more than 300 E. variegatus over the course of two seasons and never found evidence that X-disease phytoplasma was replicating in their mouthparts. In the first generation (May/June) some Colladonus spp. (C. m. reductus and C. geminatus) leafhoppers had X-disease phytoplasma in their guts, but none had phytoplasma in their heads. This suggests they can acquire phytoplasma in the first generation, but the long latency prohibits transmission then. The likelihood that a Colladonus spp. leafhopper had X-disease phytoplasma replicating in its mouthparts was highest in the second (August) and third generation (October). Evaluation of X-disease acquisition by leafhoppers feeding on highly infected cherry trees for 3 days led to shorter time to transmission than previously reported, suggesting that the latency period is dose dependent. Further analysis of leafhoppers feeding on plants varying in phytoplasma titer and for different time periods will help to better understand the latency period in different scenarios.
