| Hazelnut -- Eastern Filbert Blight | ||||
| Cause:
Anisogramma anomala, a fungus that has infected hazelnut orchards throughout the Pacific Northwest. The fungus has a life cycle of 2 or more years including a 12- to 15-month latent period when no symptoms are visible. In spring, spores are released in a sticky, white ooze in wet weather. Wind-driven rain and splashing droplets spread spores to young, developing shoots. Infection occurs in wet weather from budbreak through shoot elongation. Spores penetrate immature epidermal cells in the region behind the meristem where cell elongation occurs. Neither wounds nor natural openings on hazelnut trees have been shown to serve as sites of entry for the fungus, and it is not spread through the nuts.
Stroma begin to develop the second summer after infection. Ascospores begin to mature in fall as the rainy season begins. Several hours of continuous rain are needed for ascospore release. Stroma will continue to sporulate, even after the diseased branch is removed from the tree, until the canker dries out completely. Ascospores are shed all winter but cannot infect hazelnuts until spring. Heavy rains during the dormant period have been associated with reduced spore catches in spring. New stroma develop each year as the canker continues to expand around and along the branch. Numerous new infections also occur each succeeding year. The pollinizer 'Daviana' and the cultivars 'Ennis' and 'Du Chilly' are highly susceptible to this disease. Most wild or escaped seedlings also are susceptible because they may have 'Daviana' as a parent. 'Casina' is susceptible as is 'Negret'. The main industry cultivars ‘Barcelona’, ‘Butler’, ‘Hall’s Giant’, and ‘Willamette’ have intermediate susceptibility. ‘Lewis’ and ‘Clark’ are resistant but can become infected through repeated exposure to EFB. ‘Santiam’ and 'Yamhill' have complete resistance. Contorted ornamental hazelnuts can also be infected and have been found in Oregon in Pendleton, Portland, Corvallis, and Eugene. The red leaf ornamental contorted cultivar 'Red Dragon' also has complete resistance. The native Corylus conuta var. californica and C. conuta var. conuta and the Turkish hazel (C. colurna) do not appear susceptible to the disease. Strains of Anisogramma anomala from eastern North America can overcome the single dominate resistance gene bread into new cultivars. There are new restrictions on commercial and ornamental hazelnut cultivars imported from out-of-state (OAR 603-052-0825). |
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| Symptoms:
Infected branches may die suddenly from July to September. Dead leaves may stay on the branch. Elongated, raised bumps begin to form on infected twigs and branches in June. When the bark is removed, the cambium below the bumps is chocolate brown. Bumps continue to expand until the fungus breaks through the outer bark in July and August. A white, oval to football-shaped fungal structure called a stroma can be seen then. As the stroma matures from August to October, it turns black and raises about 0.12 inch above the branch. Stromata occur in relatively straight rows lengthwise along the branch. Cankers enlarge along the branch each year, from a few inches on small branches up to 3 ft on larger branches of susceptible trees. Branches die back when expanding cankers girdle branches and limbs. Most of the canopy of susceptible trees is usually dead within 7 to 15 years after the first infection (if diseased limbs are not removed). Suckers, however, may be produced for many years. Orchards decline in vigor and health but may continue to be productive. Tree productivity declines slowly at first but then sharply after 3 to 10 years depending on the cultivar. At some point the orchard becomes economically unproductive as the more susceptible pollinizers or main cultivars die out, resulting in poor nut set. The disease may be confused with Eutypella cerviculata, which produces smaller black fruiting bodies on dead branches. This fungus produces diagnostic black rings under the bark, which can be found using a pocket knife. Cicada egg laying scars can also look somewhat like eastern filbert blight but are not black and look stitched. |
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Cultural
control: An integrated approach using several cultural and chemical techniques is needed for adequate disease control. Scouting for cankers twice a year is very useful; early detection aids overall control.
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Chemical
control: A total of four (4) applications is recommended to adequately protect trees. Apply starting at budswell to budbreak and continue at 2-week intervals until early May. Thorough coverage of all branches is essential. Spray each row; however, for the first application only, alternate row applications may provide acceptable coverage. The disease kills trees slowly, so the yield benefits obtained from fungicidal protection are not realized for 3 to 4 years after application.
For non-bearing trees only. Non-bearing is defined as trees that will not produce a harvestable crop within 12 months after the last application.
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| Notes:
Injection of various chemicals into trees using various techniques was not successful in reducing or eliminating canker spread within trees.
Although OxiDate is registered it will not control this disease due to its short residual activity. Although Messenger is registered it is not recommended due to poor efficacy in fungicide trials. |
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References: Johnson, K.B., S.A. Mehlenbacher, J.K. Stone, J.W. Pscheidt, and J.N. Pinkerton. 1996. Eastern filbert blight of European hazelnut: It's becoming a manageable disease. Plant Disease 80:1308-1316. Pscheidt, J. W. 2008. Eastern Filbert Blight Help Page. http://oregonstate.edu/dept/botany/epp/EFB/ |
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| Content edited by: Jay W. Pscheidt on January 1, 2009 | ||||
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