Eastern Filbert BlightEastern Filbert Blight Help Pagelink to the home page

ManagementLocationLife CycleRiskReferences

Helping farmers find, destroy, and manage EFB


Spread of EFB

Jay W. Pscheidt, John N. Pinkerton

Eastern Filbert Blight can be spread in a variety of ways. Spread can be between regions, orchards, or trees.

Spread Between Regions

Long distance spread between regions can occur via the transport of infected nursery stock. For example, infected ornamental contorted filberts, Corylus avellana var. contorta, have been found from Corvallis to Eugene and even in Pendleton, OR. All of these trees originated from nurseries located in the heavily infected regions near Portland. We believe that this was the way EFB may have been originally introduced into the Pacific Northwest from the East Coast.

Hazelnut growers need to be concerned about this type of spread since it can also happen with orchard stock. There was a situation near Salem where a grower discovered two trees infected with EFB in a newly planted hazelnut orchard. It was suspected that the trees were infected in the nursery before shipment. Early detection, quick scouting and tree removal on the part of many people helped eradicate EFB from that orchard.

Quarantines are used to help prevent this type of spread. Although not perfect, quarantines against shipment from the East Coast did keep EFB out of our western hazelnut growing areas for almost a century. Quarantines have also been imposed within Oregon to prevent movement of nursery stock from the northern Willamette Valley to the mid and southern valley areas. However, some shipments of infected stock still continued. In December of 1995 the Oregon Department of Agriculture, working cooperatively with the nursery and hazelnut industries, imposed a five-year moratorium on retail and landscape sales of all Corylus in Oregon to prevent the spread of EFB. Corylus stock cannot be moved from infected areas (north of Woodburn and McMinnville) to uninfected areas. The moratorium does not affect shipments out of Oregon.

Spread Between Orchards

Spread between orchards has been a hotly debated topic since EFB was first discovered in the Willamette Valley. Before we knew much about the biology of the fungus, there was a lot of speculation about movement of EFB in nuts, nut bins, debris on harvesters, or by birds.

Nuts are not a source of EFB and thus movement of them does not pose a risk to the industry. Twigs with cankers can be moved long distances if accidentally transported in harvest bins or on orchard equipment. Debris from nut bins should be disposed of by burning or burying. Farm implements should be inspected and cleaned before transport from infected to clean orchards.

The bird theory is a favorite among growers who have observed the habits of crows and blue jays within and between orchards. There is only circumstantial evidence to support or deny any bird involvement with this disease. Small twigs infected with EFB have been observed in a water basin (part of a meteorological station) at the Vancouver, WA experiment station. Birds were also observed to use this basin as a birdbath. If birds do transport infected twigs, it would likely be for nesting material and thus would not be transported far. Songbirds set up small (1 acre) territories during the spring nesting season. In addition, blue jays generally nest in conifers. Movement of EFB spores via bird feet is considered highly unlikely if not impossible.

The fungus is perfectly capable of spreading on its own without help from man or animals. An EFB spore is about 10 times smaller than a hazelnut pollen grain. The spores can become airborne by wind during periods of rain. From 1989 to 1992, 1 year-old trap trees were planted from 10 to 150 meters (about 500 feet) upwind of an infected orchard to see how far spores might travel once airborne. The number of infected trees found at 10 meters was not significantly different than the number of trees found at 150 meters. These data indicate that EFB spores can be moved from infected areas by wind and remain infective until they land on other hazelnut trees.

Spread Within Orchards

The potential for spread is great within an orchard. Spores are ejected into the wind after cankers are wet for as little as 5 hours. There may be some spores that are rain splashed onto neighboring trees or washed down the scaffolding to growing shoots or suckers along the trunk. Most of the spores, however, are by forcibly ejected (squirted) out of the perithcium. Patterns of diseased trees within an orchard show that most local spread of the disease occurs to the northeast. Many of the rainstorms that occur during the spring move from the southwest to the northeast. This has been a fortunate characteristic of this disease since the epidemic began in the northeast part of our growing area. The spread of the disease into our southern production areas has been slowed greatly by these prevailing wind patterns.

An infared picture of an infected hazelnut orchard. The white X symbol indicated where infected trees were first found. The blue diamonds indicated where infected trees were found the following year and the yellow boxes indicate where trees were found the year after that. Note the pie shaped pattern of spread which is to the north-east along with the prevailing storm track.
An infared picture of an infected hazelnut orchard.
Photo by John Pinkerton, 1991.

Life Cycle Tour
Previous / Next / Animated


Eastern filbert blight on the ornamental contorted filbert.
Eastern filbert blight on the ornamental contorted filbert.
Photo by Jay Pscheidt, 1997.

From 1989 to 1992, 1 year-old trap trees were planted from 10 to 150 meters (about 500 feet) upwind of an infected orchard to see how far spores might travel once airborne. The number of infected trees found at 10 meters was not significantly different than the number of trees found at 150 meters. These data indicate that EFB spores can be moved from infected areas by wind and remain infective until they land on other hazelnut trees. Results of a study

Oregon State University and Extension Service logos


For more information
contact OSU Faculty.

More sites related to Hazelnuts

Disclaimer


Management
Location
Life Cycle
Risk Assessment
References

Home