Cause Two fungal species, Fusarium avenaceum and F. sambucinum, cause cone tip blight and the disease has been found in OR, WA, and ID. These two fungi can survive in soil or plant debris. Field observations suggest that the onset of disease appears to be more severe in sites with more humid conditions during cone development, especially with overhead irrigation. Spores may come in contact with hop flowers during the burr stage but disease isn't evident until much later. Little information is available on the epidemiology of hop cone tip blight. The disease appears to be most severe on the variety 'Nugget' but has also been a problem on the varieties, 'Chinook' and 'Willamette'.
Symptoms Affected cones turn from green to brown as they reach full maturity. Browning starts at the tip and moves up the cone toward the stem. Affected cone area varies; only the very tip may be brown, but all the bracts in the whorl tend to be affected. When the bracts are removed, necrosis of the portion of the strig associated with affected bracts is usually evident.
Cultural control Specific control measures have not been researched; however, measures that reduce Fusarium canker may help reduce cone tip blight.