Control of Eastern Filbert Blight

Final Report for SW00-047

Project Type: Research and Education
Funds awarded in 2000: $81,477.00
Projected End Date: 12/31/2003
Matching Non-Federal Funds: $43,870.00
Region: Western
State: Oregon
Principal Investigator:
Jay Pscheidt
Department of Botany and Plant Pathology
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Project Information

Abstract:

The management of eastern filbert blight (EFB) using DMI or strobilurin fungicides alone or in combination was effective. A model based on branch wetness, called GrammaCast, used fewer applications of fungicide and was as good as or worse than the standard program. Late fall or spring injections of fungicides will not be of benefit for the management of EFB. There were 3 Collembola, 7 mites and 13 fungi identified in association with EFB stroma. All research and extension projects were communicated to the hazelnut industry in a wide variety of ways.

Project Objectives:

1. In cooperation with hazelnut growers, establish field and greenhouse trials designed to evaluate new chemicals for effectiveness against EFB.

2. Develop and evaluate an easy-to-use ascospore forecasting model in cooperation with hazelnut growers to help determine the need for late spring applications of fungicides.

3. Evaluate tree injection technology for the therapeutic treatment of trees already infected with EFB.

4. Document and describe organisms associated with EFB cankers. Evaluate the potential of various organisms for biological control of EFB.

5. Disseminate results to the hazelnut industry in a variety of user friendly formats.

Introduction:

Eastern filbert blight (Anisogramma anomala) continues to spread in western Oregon and threatens sustained production of European hazelnut. A major new area in the southern Willamette Valley was found infected during the summer of 2003. Eastern filbert blight (EFB) can render an orchard unproductive within seven years. Hazelnuts are produced in the Willamette Valley on 30,000 acres, representing 99% of the US production.
Growers, in concert with researchers and extension people, have developed a plan and have allocated a large percentage of their resources to keep the industry viable during their current crisis. The plan is two pronged, including the development and propagation of an eastern filbert blight (EFB) immune variety (2,9). This active breeding program at OSU is currently developing the cultivars needed to resist the fungus (2, 4, 5, 7). Resistant cultivars hold great promise but still contract EFB and must still be scouted, sprayed, and pruned. For current orchards, the goal is for the development and use of innovative cultural practices to mitigate the current southward movement of this disease. This will help sustain hazelnut production until the release and widespread use of immune varieties. Without implementation of such a plan, our nation will lose an industry that infuses from 15 million to 40 million dollars into the economy each year and provides families an opportunity to keep the rich Willamette Valley soil productive for generations to come. In addition, information gained from the hazelnut industry will be available for use as a prototype for other crops with similar disease problems.
Fungicides are critical in the overall plan so that growers can plan to stay viable through the transition to new immune varieties. The loss of Bravo 720 could be a major setback in the industry’s control efforts (3, 6, 12). In addition, the spring of 1993 was unusually wet, resulting in poor EFB control and indicating a need for the registration of a systemic fungicide with curative activity (2). Growers deem it important to test and register chemicals that are effective, less expensive, and continue to meet the standards proposed by EPA. The added costs of fungicide use can only be justified if they are examined in the total picture through the EFB crisis. Without their use, EFB can cause yields to decline to below economically viable levels within seven years.
A forecasting model with fungicide application rules could help reduce costs and encourage more growers to implement control tactics. A prototype ascospore forecasting model was being developed (8), based on several years of spore trapping information at several sites. During years of high rainfall prior to and through budbreak fewer applications may be needed.
The use of microorganisms or their by products (biological control) against the fungal canker (EFB), has not been formally investigated. Several fungi, including Paecilomyces sp., Phomopsis sp., Glicocladium roseum, and Fusarium sp., have been found in close association with EFB cankers (Stone, unpublished). Some of these can be seen as white growths within old cankers. Paecilomyces and Gliocladium both occur naturally as fungal parasites. Other organisms may also be associated with EFB cankers including slugs (Pinkerton, unpublished), bacteria, viruses, insects such as fungal feeding Collembola (Pscheidt, unpublished) or mites. An understanding of why these organisms are in these cankers may be useful.
Growers are committed to keeping hazelnut production viable through the EFB crisis by identifying potential methods for control, testing efficacy and economics of these methods in orchard situations and communicating the program to every hazelnut grower and operator in the Northwest. Using a newly developed computer model for hazelnut production (Seavert and Olsen, unpublished), growers can determine which methods of control are feasible with their individual economic circumstances. With the help of this integrated industry plan, hazelnuts can be farmed in the Willamette Valley for generations to come.
Research into the biology of this disease has determined many important factors that need to be considered when attempting to manage EFB. The first important discovery was that it takes 2 years for symptoms to develop after infection (1). The next important discovery was determining when and how infection occurred. Hazelnut trees are susceptible to infection from budbreak (early March) until dry weather prevails in late spring (usually late May) (13). Neither wounds nor natural openings on hazelnut trees have been shown to serve as sites of entry for this fungus (13). As vegetative stems mature, they become resistant to infection. Chemical control measures must target the expanding shoot tip (12, 13).
Spores are ejected into the wind after cankers are wet for as little as 5 hours (8). Some spores are rain-splashed or washed down the tree to growing shoots or suckers. Within an orchard, most local spread occurs to the northeast. Although spores are dispersed throughout the winter and spring, individual spores, once released, do not survive for long periods of time. Thus, spring releases of spores are important, and they occur frequently during March, April, and May (2, 8).
The protective fungicide chlorothalonil (Bravo Weather Stik) has provided outstanding control of eastern filbert blight in a multitude of field, greenhouse, and laboratory experiments (3, 12). Other fungicides have not provided as consistent control such as copper-based fungicides (11) or have different modes of action such as fenarimol (Rubigan EC) or propiconazole (Orbit). The best disease control has been obtained with multiple fungicide applications beginning at bud break and continuing at 2-week intervals through April into early May (12). Bravo Weather Stik has been the most effective when applied early in the spring when little green tissue is present on the trees. Rubigan and the other locally systemic fungicides appear to be more effective in mid to late spring after new green leaves and stems have expanded.
Grower history as well as controlled research indicates cultural control methods have been ineffective unless chemical controls have also been incorporated into the experimental design (2).

References:

1. Gottwald, T.R. and Cameron, H.R. 1979. Studies in the morphology and life history of Anisogramma anomala. Mycologia 71:1107-1126.

2. Johnson, K.B., Mehlenbacher, S.A., Stone, J. K., Pscheidt, J.W. and Pinkerton, J.N. 1996. Eastern Filbert Blight of European Hazelnut. It’s Becoming a manageable disease. Plant Disease 80:1308-1316.

3. Johnson, K.B., Pscheidt, J.W., and Pinkerton, J.N. 1993. Evaluation of chlorothalonil, fenarimol, and fusilazole for control of eastern filbert blight. Plant Disease 77:831-837.

4. Mehlenbacher, S. A. and Thompson. M.M. 1991. Four Hazelnut Pollenizers Resistant to eastern filbert blight. Hortscience 26:442-443.

5. Mehlenbacher, S.A., Pinkerton, J.N., Johnson, K.B. and Pscheidt, J.W. 1994. Eastern Filbert Blight in Oregon. Acta Horticulturae 351:551-557.

6. Olsen, J.L.; Fisher, G.C.; and Pscheidt, J.W. 2003. Hazelnut Pest Management Guide for the Willamette Valley. Oregon State Extension Service. EM 8328.

7. Pinkerton, J.N.; Johnson, K.B.; Mehlenbacher, S.A. and Pscheidt, J.W. 1993. Susceptibility of European hazelnut clones to eastern filbert blight. Plant Disease 77:261-266.

8. Pinkerton, J.N., Johnson, K. B., Stone, J. K. and Ivors, K.L. 1998. Factors Affecting the Relaease of Ascospores of Anisogramma anomala Phytopathology 88:122-128.

9. Pscheidt, J.W. and Ocamb, C. M. Senior editors. 2004. Pacific Northwest Plant Disease Management Handbook. Oregon State Extension Service. 600 pp.

10. Pscheidt, J. W. and Cluskey, S. 1996. Eastern Filbert Blight Management Survey. Proceedings of the Nut Growers Society of Oregon, Washington and British Columbia. 81:53-60.

11. Pscheidt, J. W. 1995. Will Hazelnuts Go Extinct in Oregon Again? Proceedings of the Nut Growers Society of Oregon, Washington and British Columbia. 80:70-77.

12. Pscheidt, J.W. and Johnson, K.B. 1993. A Chemical Control Program for Eastern Filbert Blight. Proceedings of the Nut Growers Society of Oregon, Washington and British Columbia. 78:84-88.

13. Stone, J.K.; Johnson, K.B.; Pinkerton, J.N. and Pscheidt, J.W. 1992. Improved understanding of the infection biology of Anisogramma anomala on European hazelnut. Plant Disease 76:348-352.

Cooperators

Click linked name(s) to expand
  • Richard Birkemeier
  • Ron Chapin
  • Kenneth Johnson
  • Bob Jossy
  • David McAdams
  • Ben Mitchell
  • Jeff Olsen
  • Ross Penhallegon
  • John Pinkerton
  • Lynn Royce
  • Jeffery Stone

Research

Materials and methods:

Objective 1

The management of eastern filbert blight (EFB) using different chemicals was investigated in the field on young trees. Young trees were grown from stool beds located at the OSU Botany and Plant Pathology Field Laboratory near Corvallis, Oregon. These healthy, 2-year-old trees were planted at the North Willamette Research and Extension Center during January or February of 2000, 2001, and 2002. A trellis-like structure was built to suspended EFB inoculum above trees. These trees were sprayed with fungicides using a backpack sprayer during early spring growth (using a randomized complete block design), and then tended until evaluated for EFB cankers the following year.

Objective 2

Several field trials were initiated to test the rules developed for the forecasting model, now called GrammaCast. The model has the following rules: Initiate an application of a protectant fungicide (such as Bravo Weather Stik) at bud break. Wait 2 weeks then monitor branch wetness. When > 20 hours branch wetness is detected then initiate an application of a DMI type fungicide (such as Orbit). Once a DMI is applied wait 2 weeks and begin monitoring branch wetness again. If no periods of > 20 hours wetness are detected through the first week of May then no additional fungicides are required.

Two-year-old trees were planted in the spring in three different grower orchards that were heavily diseased with EFB. A total of 8 trials were conducted over a 3-year period. Treatments consisted of a full spring season spray program of three Bravo Weather Stik applications, an early season spray program of one Bravo Weather Stik application with subsequent applications of Orbit, Procure, or Rubigan based on the forecasting model and non-treated check trees. The number and length of cankers were recorded and analyzed the following year.

Spore traps were also deployed to monitor the amount of spores being dispersed between each fungicide application. Each spore trap consisted of a 2.3 meter long 1/2 inch PVC pipe split in half lengthwise, supported by 2 metal posts, and angled at 20 degrees to drain into a covered 16- liter collection bucket. Each bucket contained 200 ml of 50% copper sulfate v/v as a spore preservative and germination inhibitor. Rainwater from the traps was collected by swirling the contents and pouring into a volumetric cylinder to measure the total volume of rainwater collected. Approximately 500 ml of the rainwater was collected for laboratory analysis and the copper sulfate solution was replenished after each collection. The rainwater was filtered first through a 20 um sieve then through a cellulose nitrate filter with 0.8 um pore size. This filter paper was placed on a microscope slide, stained with 0.05% (v/v) trypan blue in lactoglycerine. The number of ascospores on filters was then determined using a light microscope at 400X and used to calculate the number of ascospores collected per M2 of trap surface.

Objective 3

Our objective was to determine if fall injection of fungicides into hazelnut trees could limit or reduce EFB canker extension. All trees were injected using the Sidewinder Tree Injector (Backpack Unit, P.O. Box 1111, 2/8 Project Ave., Noosaville, Queensland, 4566, Austrailia). A commercial block of moderately diseased ‘Ennis’ trees planted in 1991 on a 15 x 17 ft spacing near Keizer, OR was selected for injection. Treatments were arranged in a randomized complete block design with 6 single tree replications. Trees were assigned to blocks based on similarity in overall size, trunk diameter, trunk health, and number of EFB cankers found in the canopy. Each tree was injected with 5 ml water or 5 ml of undiluted Orbit EC or a 1% dilution of Folicure 3.6 F per injection site in Sep. A total of 5-6 injections were made around the base of each tree approximately 2-3 inches from each other with special focus on root flair areas. A pressure of approximately 90 psi was maintained until the entire 5 ml volume was delivered (which ranged from 10 to 15 minuets per injection site). Each injection hole was then filled with a threaded plastic plug. Trees were observed for phytotoxicity until 100% leaf fall and during the following growing season. A total of 10 EFB cankers per tree were marked and examined for length of EFB cankers prior to the next growing season. Distal and basipetal current season elongation was then determined in Jul.

A similar trial using the same treatments was conducted in a commercial block of moderately diseased ‘Barcelona’trees planted in 1984 on a 20 x 20 ft spacing near Banks, OR. Treatments were arranged in a randomized complete block design with 4 single tree replications. Each tree was injected with 5 ml water or 5 ml of a 10% dilution of Orbit EC or a 10% dilution of Folicure 3.6 F per injection site. A pressure of approximately 90 psi was maintained until the entire 5 ml volume was delivered (which ranged from 20 to 25 minuets per injection site). A total of 10 EFB cankers per tree were marked with red paint in Dec. for examination later during the following summer. A total of 10 EFB cankers per tree were marked and examined for length of EFB cankers prior to the growing season. Distal and basipetal current season elongation was determined in Jul.

Objective 4

Cankers from around Oregon were collected and examined microscopically for the presence of different fungi. Isolations of various fungi onto standard nutrient agar plates was accomplished. Fungi were identified using traditional mycological techniques.

Cankers will also be collected and examined periodically during the year for insects and mites. Insects and mites were transferred to small containers with hazelnut stem sections to see if individual colonies can be established. The location, number, and behavior of these organisms was observed. Each insect or mite was identified based on morphological characteristics.

Objective 5

All research and extension projects are currently communicated to the hazelnut industry in a wide variety of ways. These same outlets were utilized as the project unfolded. Results were communicated through various grower organizations, such as the Nut Growers Society, and functions that were well attended including meetings, workshops, and summer tours. Existing publications that were utilized include several different newsletters, fact sheets, the hazelnut pest management guide (6), the Pacific Northwest Plant Disease Control Handbook (9), and the On-line Guide to Plant Disease Control. An EFB World Wide Web site that is linked to the grower organization’s current Web site was also very useful.

Research results and discussion:

Objective 1

Many of the DMI type fungicides with locally systemic activity were effective (Table 1). Products such as propiconazole (Orbit), tebuconazole (Elite), fenbuconazole (Indar), and triflumizole (Procure) have good activity against EFB when used alone. Greenhouse studies have shown this group of chemicals to have kickback activity against EFB. Many infections can be cured when these chemicals are applied up to 72 hours after inoculation with the fungal pathogen.

The next generation of agricultural fungicides, the strobilurins, are beginning to be registered in various fruit markets including hazelnuts. Both trifloxystrobin (Flint) and pyraclostrobin (Cabrio/Pristine) continue to show excellent protective action in the field. Both have received EPA registration for use on hazelnuts due to data developed in this project.

Several products have shown little to no activity against EFB including Elevate, JMS Stylet Oil alone, Lime Sulfur, Messenger (harpin), and Quintec. Some of these were not expected to do well but others could have been useful. Lime Sulfur is also used for Big Bud Mite control at the same time applications are needed for EFB. We may need to investigate tank mixes to see if there are any compatibility problems with lime sulfur and various fungicides.

2. Develop and evaluate an easy-to-use ascospore forecasting model in cooperation with hazelnut growers to help determine the need for late spring applications of fungicides.

A model (called GrammaCast) was developed, based on length of branch wetness due to rain, to help decide when to deploy fungicides.

Twice, trees treated with various fungicide combinations in the North Plains (2002) and Newburg (2003) locations were oversprayed by the commercial operation adjacent to the plots. This resulted in no usable information during those years.

GrammaCast generally called for only 2 applications per year. An additional (3) application was needed at the Newburg location and only 1 was required during 2003 at the Mission Bottom location. The number of cankers on trees treated according to GrammaCast was significantly lower than non-treated trees except for Royal trees in 2003 (Tables 2 and 3). GrammaCast treated trees had the same or significantly fewer cankers than conventionally treated trees in 4 out of 6 trials. Average disease control was 71% for Ennis and Royal trees treated in the conventional way while it was 69% for trees treated according to GrammaCast.

Some growers who choose to avoid expenses as much as possible have developed the single Bravo approach. Only one Bravo Weather Stik application is made a bud break. Disease control averaged 43% with this single application which was significantly different from non-treated trees in 4 out of 6 trials (Tables 2 and 3). GrammaCast treated trees had fewer cankers than trees treated with a single Bravo application in only 2 trials.

Although GrammCast can be released, after several years testing it has not preformed as well as a simple calendar-based protection program. Fungicides can be saved but at the risk of more disease some years.

3. Evaluate tree injection technology for the therapeutic treatment of trees already infected with EFB.

Water injections were fairly quick while the fungicides took about 10-25 min/injection site. Injection times for Orbit solutions were generally faster. No phytotoxicity was observed on the leaves or at the injection holes of any injected tree at either site during the fall or dormant season. However, both Ennis and Barcelona trees injected with Orbit showed oozing around the injection site during the 2000 growing season. This oozing is characteristic of substantial cambial damage or death near the injection site. No significant difference in original canker length was detected in either set of trees indicating a uniform group of cankers used for comparison (Tables 4 and 5). Cankers on Ennis trees expanded from 212 to 237% while cankers on Barcelona trees expanded from 152 to 199%. Canker expansion on fungicide injected trees was not significantly different from cankers on water treated trees in either trial location.

Due to lack of EFB control it does not appear that late fall or spring injections of fungicides will be recommended.

4. Document and describe organisms associated with EFB cankers. Evaluate the potential of various organisms for biological control of EFB.

A total of 13 fungal isolates were found and identified in association with EFB stroma. Both Epicoccum purpurascens and Ulocladium sp. were of interest due to their past use in biocontrol projects and resistance to commonly used fungicides.

We were interested in Collembola insects since they are known fungal feeders and have been used in past biocontrol projects of soilborne plant pathogens. Three different types of Collembola were found in various samples. In general these insects were not found within the stromatic tissue of the EFB fungus. They were found all over the surface of the cankers but most were found along the canker margins next to and associated with the ridge of live host callus tissue.

At least 7 different mites were observed in various samples. Some were predators of other mites, some were fungal feeders, but one was found in close association within the stroma of EFB. Czenspinskia lordi were found in high populations on all three collections and was located in large groups within the blight stroma.

After understanding the difficulties and complexities of developing a successful biocontrol project, growers have become uninterested in continued pursuit of this line of research. No further studies will be done on this objective.

5. Disseminate results to the hazelnut industry in a variety of user friendly formats.

See “Publications and Outreach” section below.

Research conclusions:

We have been able to generate data directly responsible for the successful application and generation of section 18 emergency use labels for Elite in 2001, Procure in 2002, and for Orbit in 2003. In addition, full section 3 registrations of Flint (2003) and Pristine (for 2004) have been obtained. The development of the forecasting system, GrammaCast, has helped to time fungicide applications and teach growers about environmental variables favorable for disease development. Time will tell if this will translate into real monetary saving. Development of data that show therapeutic treatment of infected trees with fungicides is ineffective will help avoid unproductive disease management activities. Biological control of EFB may be possible but not without many more years of development. By that time, new immune cultivars would make it unnecessary.

Participation Summary

Educational & Outreach Activities

Participation Summary

Education/outreach description:

All research and extension projects are communicated to the hazelnut industry in a wide variety of ways. Results have been communicated through various grower organizations, such as the Nut Growers Society, and grower meetings including a winter “Find It” workshop and an annual summer tour. Publications utilized include the Hazelnut Pest Management Guide for the Willamette Valley (see web address below), the Fruit and Ornamental Disease Management Program, the Pacific Northwest Plant Disease Management Handbook, and the On-line Guide to Plant Disease Control (see web address below ). The Eastern Filbert Blight Help Page has also been very helpful getting up-to-date information out on a timely basis (see web address below).

The following web sites are of direct interest to hazelnut growers wanting information on the control of EFB.
http://www.orst.edu/dept/botany/epp/EFB/
http://plant-disease.ippc.orst.edu/disease.cfm?RecordID=578
http://eesc.orst.edu/agcomwebfile/edmat/html/EM/EM8328/EM8328.html

Project Outcomes

Project outcomes:

Traditional economic analysis showing yield benefit for management input is not possible within the time frame of this project. Since the disease has a 2-year life cycle and yield loss takes 5 or more years to even begin to manifest itself it will take several years for the real economic benefit to be realized. Our last section 18 for Orbit has been very popular, in part, because of its lower cost per acre. In direct comparisons the cost of the standard 3 applications of Bravo is $92.34/acre while that for Orbit is $30/acre. This alone has saved the growers money while not changing disease control efficacy.

The forecasting program GrammaCast combined with the registration of cheaper fungicides could have had a large financial impact on hazelnut growers. The average cost of the standard program is $92.34/acre as described above. GrammaCast averaged $37.78/acre but at the risk of much less disease control (some data from outside this study). Some growers who choose to avoid expenses as much as possible have developed the single spray approach which we know will be disastrous. Although they save $7/acre over GrammaCast, it results in less than 50% disease control.

Farmer Adoption

Finding cheaper and more effective chemistry has shifted grower use of chemicals. Emergency section 18 registrations have shifted as new information is developed and new regulatory road blocks are encountered. Requests have moved from Rubigan (1993-1999) to Orbit (1999, 2003 and 2004) to Elite (2000 – 2002) to Procure (2001-2003). Our ability to switch from product to product and maintain needed disease management tools is a direct result of the data generated by this project. Grower adoption of the forecasting program will take more time as results are still being evaluated.

Grower discussions during a recent Oregon Hazelnut Commission meeting indicate that this project was rated as a high priority. During an informational meeting near Eugene, growers experienced in dealing with EFB said the use of fungicides and pruning was essential to maintain profitability.

Recommendations:

Areas needing additional study

Long-term whole orchard trials are needed to fully understand disease control and yield loss. These trials need to be conducted over a 5- to 10-year period. Although not popular with funding agencies it would help produce the data needed to help growers make critical decisions about the long-term management of their orchards.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.