ARS | Publication request: A Case Study: Significance, Epidemiology, and Management of Hop Viruses.

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2008
Publication Date: June 1, 2008
Citation: Pethybridge, S.J., Turechek, W., Madden, L.V. 2008. A case study: significance, epidemiology, and management of hop viruses. Phytopathology. 98(6):S189.

Technical Abstract: Hop latent carlavirus (HpLV), Hop mosaic carlavirus (HpMV), and Apple mosaic ilarvirus (ApMV) are viruses that have been shown to have deleterious effects on cone yield and brewing organic acids in several cultivars in Australian hop gardens, and pose a significant threat to the continued production of high yields. The means by which these viruses were spread within and between hop gardens was hypothesized from results of spatial, spatio-temporal, and association analyses, and later confirmed with additional experiments. Spatial analyses included ordinary runs, join-count, and radial correlation, and a stochastic spatio-temporal model was fitted to the data using Markov Chain Monte Carlo (MCMC) methods. Associations among these viruses were assessed using the Jaccard similarity index, Spearman’s rank correlation coefficient, and spatial analysis by distance indices (SADIE). Combined results suggested spread of carlaviruses was predominantly within gardens, especially along rows. However, for HpMV epidemics in cultivar Agate, infections initiated from outside the garden, and immigrant viruliferous aphids were also important. Furthermore, the species of aphids that contributed to foci initiation within gardens were determined, the numbers of which were influenced by cultivar and location. A strong positive association between HpLV and HpMV was also found in all cultivars and at all locations, suggesting a common aphid vector species, despite the absence of the hop aphid, Phorodon humuli. ApMV incidence was also predominantly autocorrelated within gardens. Further experiments subsequently demonstrated transmission through pruning (simulated slashing for basal growth control), shoot contact, and root grafting. Recommendations for virus management from this research include the use of virus tested material for garden establishment and dessicant herbicides for basal growth control throughout the season.