See:
Hazelnut Cultivar Susceptibility
Cause Xanthomonas arboricola pv. corylina (formerly Xanthomonas campestris pv. corylina), a bacterium that attacks buds, leaves, branches, and trunks. Occasionally it attacks nuts but seldom invades roots. Tree mortality due to this disease is commonly found in orchards the first few years after planting. The most serious phase of the disease is trunk girdling and killing of trees up to 8 or 10 years old. Generally only 1- and 2-year-old twigs are attacked and killed. Rain splash or the movement of infected nursery stock spreads the bacteria. Seedborne transmission has been reported but no data is presented to support the claim. Infections are indirect, through wounds or by bacterial invasion of blighted buds and shoots of current-season growth. The disease has been associated with high stress sites and dryland production.
In Italy, higher disease incidence was found in regions with higher rainfall and a greater difference between high and low temperatures during frost events. They also found higher disease incidence for soils with higher nitrogen levels.
Symptoms Small, angular or round, yellowish green, water-soaked spots develop on leaves, later turning reddish brown. Buds may turn brown and fail to leaf out. Shoots may develop but are infected. The first infections on current-season stems consist of dark green water-soaked areas on bark, which turn reddish brown. Lesions may girdle stems and kill them. Dead leaves often cling to girdled stems a long time. Lesions or cankers may extend into the main scaffold or trunk. Use a pocket knife to determine the extent of canker development. Lesions may be wet and ooze in spring. Can be confused initially with flathead borer damage.
Cultural control
- Plant pathogen-free nursery stock in early winter. Do not let roots dry out.
- Choose resistant cultivars for planting.
- Prune out infected twigs and branches. Make cuts 2 to 3 ft below affected branches. Soak pruning tools between cuts with shellac thinner (70% ethyl alcohol), 10% Clorox (which is corrosive), Lysol, ZeroTol, Oxidate, or X3. Disinfestants work better on clean equipment with long contact times. Use the two pruners method: having one soaking in the solution of choice while using the other; then switch pruners, leaving the one you just used to soak, and the one that had been soaking, to continue pruning. If used as a soak, change solutions every 2 to 3 hours.
- Control sunburn during summer using shields or white paint on trunks.
- Mulch around the base of newly planted trees with chipped, composed tree debris to reduce moisture stress.
- Irrigate during the first 3 summers after planting to reduce moisture stress.
- Apply nitrogen fertilizer in the spring based on leaf tissue analysis the prior August.
- A hot water soak of nursery stock for 45 min at 108°F was effective to reduce bacterial populations.
Chemical control Start applications in the nursery and/or after planting a new orchard. Apply sprays in late August or early September before the first heavy rains. If fall rains are heavy, apply another spray when 75% of the leaves have dropped. Note that most copper products do not allow use until after harvest. Spring applications do not improve disease control over fall applications alone and spring applications alone helped a little in 2 out of 5 trials. Although copper-resistant bacteria were not found among isolates collected in 2018-19, minimize copper use so resistant bacteria do not develop.
- Badge X2 at 7 to 20 lb/A. Oregon and Washington only. Can be used past harvest. Group M1 fungicide. 48-hr reentry. O
- Basic Copper 53 at 8 to 11.3 lb/A plus 1 pint superior-type oil/100 gal water as a postharvest spray. 48-hr reentry. O
- Bordeaux 6-3-100. Group M1 fungicide. O
- ChampION ++ at 7 to 10.5 lb/A Can be used only after harvest. Oregon and Washington only. Group M1 fungicide. 48-hr reentry. O
- C-O-C-S WDG at 11.6 lb/A plus 1 pint superior-type oil/100 gal water. Can be used only after harvest. Group M1 fungicide. 48-hr reentry.
- Copper-Count-N at 8 to 12 quarts/A. Can be used only after harvest. Group M1 fungicide. 48-hr reentry.
- CS 2005 at 64 to 128 oz/A. Group M1 fungicide. 48-hr reentry. O
- Cueva at 0.5 to 2 gal/A after harvest. Oregon and Washington only. Group M1 fungicide. 4-hr reentry. O
- Cuprofix Ultra 40 Disperss at 10 to 15 lb/A. Oregon and Washington only. Group M1 fungicide. 48-hr reentry.
- Grotto at 152 gal/A Oregon and Washington only. Group M1 fungicide. 4-hr reentry. O
- Kocide 50 DF at 8 to 12 lb/A plus 1 pint superior-type oil/100 gal water. Can be used only after harvest. Group M1 fungicide. 48-hr reentry. O
- MasterCop at 6 to 9 pints/A. Group M1 fungicide. 48-hr reentry.
- Monterey Liqui-Cop at 1 to 2 Tbsp/gal water. Group M1 fungicide. H
- Nordox 75 WG at 8 to 13 lb/A. Can be used only after harvest. Group M1 fungicide. 12-hr reentry. O
- Nu-Cop 50 DF at 8 to 12 lb/A with 1pint superior-type oil/100 gal water. Can be used only after harvest. Group M1 fungicide. 48-hr reentry. O
- Previsto at 2 to 4 quarts/A after harvest only. Group M1 fungicide. 48-hr reentry. O
- Surface disinfectants such as OxiDate 2.0 at 0.25 to 2.5 gal/100 gal water are registered but have very short residual activity. Efficacy of these products has not been extensively tested in the PNW. Frequent use (every few days) is on the label, which still may not be effective during conditions favorable for bacterial growth and infection.
Notes Surface disinfectants such as OxiDate 2.0 at 0.25 to 2.5 gal/100 gal water are registered but have very short residual activity. Efficacy of these products has not been extensively tested in the PNW. Frequent use (every few days) is on the label, which still may not be effective during conditions favorable for bacterial growth and infection.
Biological control
- Aviv (Bacillus subtilis strain IAB/BS03) at 10 to 30 fl oz/100 gal water. Do not tank mix with more than one product. Unknown efficacy. Preharvest interval not specified. 4-hr reentry. O
- Stargus (Bacillus amyloliquefaciens strain F727) at 1 to 4 quarts/A plus a nonionic surfactant. May be used day of harvest. Unknown efficacy. 4-hr reentry. O
References Lamichhane, J. R. and Varvaro, L. 2014. Xanthomonas arboricola disease of hazelnut: current status and future perspectives for its management. Plant pathology, 63:243-254.
Webber, J. B., Putnam, M., Serdani, M., Pscheidt, J. W., Wiman, N. G., and Stockwell, V. O. 2020. Characterization of isolates of Xanthomonas arboricola pv. corylina, the causal agent of bacterial blight, from Oregon hazelnut orchards. Journal of Plant Pathology 102:799-812.