Control of Eastern Filbert Blight

Control of Eastern Filbert Blight

Summary

The management of eastern filbert blight (EFB) using DMI and strobilurin fungicides was effective. A model based on branch wetness used fewer applications of fungicide and was as good as or better than the standard program. This may result in more than 50% savings in costs associated with EFB control. 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.

Objectives/Performance Targets

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

   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.

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

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

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

Accomplishments/Milestones

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

The management of eastern filbert blight (EFB) using different chemicals was investigated on young trees. Healthy, 2-year-old trees were inter-planted within heavily diseased orchards during the dormant season, sprayed with fungicides during early spring growth, then tended until evaluated for EFB cankers the following year.

Many of the DMI type fungicides with locally systemic activity, such as propiconazole (Orbit) and tebuconazole (Elite), were very effective. Although fenarimol (Rubigan) has 2-3 day kickback activity it can not be used alone with an average EFB control of 39%. Growers have not wanted to use this material and thus emergency registration requests have shifted to other products.

The average level of control when using propaconazole as Orbit resulted in 99% control. Tebuconazole (Elite) has provided an average of 87% control in many different trials. Both materials are supported by growers and have been sought after for emergency registrations.

The next generation of agricultural fungicides, the strobilurins, are beginning to be registered in various fruit markets. Products such as Abound and Sovran have been evaluated in both the field and greenhouse with disappointing results against EFB. They were best used as protectants and may still have a role in future EFB management schemes but more testing is necessary.

Several products continue to be tested including Messenger (harpin) which is reported to stimulate host defense mechanisms.

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 was developed, based on length of branch wetness due to rain, to help decide when to deploy fungicides. Trees treated every 2 weeks in the North Plains location with Bravo or according to the forecasting model with Bravo and Orbit or with just Orbit alone after a long wet period did not develop cankers. The number of cankers on trees treated according to the forecasting model with Bravo and Elite were not significantly different from zero.

All fungicide treated Royal trees planted at the Mission Bottom location had significantly fewer EFB cankers than nontreated trees. However, there were no significant differences in the number of cankers observed on Royal trees among fungicide treatments. However, Ennis trees treated with Bravo and Orbit according to the forecasting model did not develop cankers.

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

Trees were injected with fungicides during both fall and spring periods. Spring injections of Orbit showed oozing around injection sites during the growing season. With fall injections, 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 next growing season. This oozing is characteristic of substantial cambial damage or death near the injection site. 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 of any benefit for the management of EFB.

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

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.

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.

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.

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 (see web address below), the Pacific Northwest Plant Disease Control 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.orst.edu/disease.cfm?RecordID=578

http://eesc.orst.edu/agcomwebfile/edmat/html/em/em8328/em8328.html

Impacts and Contributions/Outcomes

Potential Benefits or Impacts on Agriculture

The forecasting program combined with the registration of cheaper fungicides will have large financial impact on hazelnut growers. In general, forecasting programs using 2 applications of fungicide were as good as or better than the standard program using 3 applications of Bravo. Over the last three years, the standard program would have used 9 applications of Bravo for a cost of chemical of approximately $277.02 while the forecasting program would have used 3 applications of Bravo plus one application of Rubigan plus one application of Elite for a total cost of $130.34 for chemical. A 50% reduction in cost of chemical alone should be helpful in the overall EFB battle.

Farmer Adoption and Direct Impact

Finding cheaper and more effective chemistry has shifted grower use of chemicals. Emergency section 18 registrations have shifted from Rubigan to Elite and Orbit. Grower funded projects have included an IR4 residue trial for Procure. They hope to get this product registered in the near future. Grower adoption of the forecasting program will take more time as results are still being evaluated.

Collaborators: