|Gent, David - Dave|
|Mueller Warrant, George|
|WOODS, JOANNA - Oregon State University|
|PUTNAM, MELODIE - Oregon State University|
|TWOMEY, MEGAN - Oregon State University|
Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2014
Publication Date: 6/24/2014
Citation: Gent, D.H., Mueller Warrant, G.W., Woods, J.L., Putnam, M., Twomey, M. 2014. Red crown rot of Hop in Oregon caused by Phomopsis tuberivora. Plant Health Progress. doi: 10.1094/PHP-2014-0624-01-BR.
Interpretive Summary: A disease of hop called red crown rot has been confirmed for the first time in Oregon. The disease symptoms and causal pathogen have been described previously on hop in Australia. Laboratory and field studies were conducted to determine the identity of the pathogen, conclusively establish that it can cause the observed disease symptoms on hop, and assess the distribution of affected plants in the field. Since the initial discovery, the disease has been diagnosed on two other hop farms in Oregon, but appears damaging only in certain cases. In Australia, planting of high quality rootstock, avoiding crown injury, modifying harvest practices, and fumigating have been successful in managing the disease. Further investigation of management practices and soil conditions favoring red crown rot are warranted since the disease appears economically important in some yards.
Technical Abstract: During July 2007, a hop grower in Marion County, Oregon reported weak growth and death of plants of cultivar Fuggle. Affected plants were aggregated within and among rows, and had underdeveloped lateral branches, uneven and weak bines, and chlorotic leaves; severely affected plants were dead. The pith of affected roots was reddish-brown in color, dry, and friable, with a distinct margin between diseased and healthy tissue. There was a positive association between soil pH, soil nitrogen level, and occurrence of affected plants. Phomopsis tuberivora H.T. Güssow & W.R. Foster 1932 (currently synonymous with Phacidiopycnis tuberivora [Güssow & W.R. Foster] B. Sutton 1980) was consistently recovered from affected plants. Koch's postulates were fulfilled with three isolates of the fungus, establishing the pathogen and the disease red crown rot as the cause of the damage. This is the first report of red crown rot on hop in Oregon, which may have important management implications for affected hop yards and farms.