Pacific Flatheaded Borer: An old pest is new again in Oregon’s rapidly expanding hazelnut industry

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Commodities

• Nuts: hazelnuts

Practices

• Education and Training: extension, on-farm/ranch research, workshop
• Pest Management: chemical control, integrated pest management, physical control, traps

Eastern filbert blight (EFB), endemic to the eastern US, is a disease devastating to the European hazelnut, Corylus avellana. Accidentally introduced to the Pacific Northwest in 1973, it once threatened to eliminate Oregon’s hazelnut industry (Davidson 1973), which produces 99% of US hazelnuts. Anticipating decline, the industry invested heavily in the Oregon State University hazelnut breeding program, facilitating the release of varieties with single gene resistance to EFB. This triggered major expansion of hazelnut acreage, with 39,716 acres planted with resistant varieties in the last five years (Pacific Ag Survey, personal communication 2018). The shifting of the industry from old, blighted orchards to new plantings provided opportunity for the Pacific Flatheaded Borer (PFB), Chrysobothris mali Horn (Coleoptera: Buprestidae), to cause problems for hazelnut growers. Literature suggests that PFB are attracted to stress signals emitted by establishing trees (Burke 1929). Female borers find vulnerabilities in the bark to lay their eggs. Larvae hatch and feed on the cambium layer, leading to girdling, loss of transpiration, and ultimately death of the tree. Trees that survive initial attacks can be severely weakened, risking trunk failure due to wind or nut load. Inadequate knowledge of PFB has resulted in devastating losses for some growers, risking the exponential growth of the industry. Understanding the phenology and effective management practices for PFB are critical to local hazelnut farmers success and the sustainability of the industry.

Research Questions:

1. What is the phenology of PFB in new hazelnut plantings?
2. Can traps help monitor PFB populations?
3. How can we protect young hazelnut trees from PFB?

Our research will address the insufficiencies regarding monitoring and management options for PFB. We will discuss our findings at nut grower meetings and workshops that typically attract hundreds of growers. Education in emergence timing, population counts, and effective plant protections will undoubtedly help our industry manage PFB.

Our goal is to provide farmers, new and established, with resources for managing the PFB, which has contributed to devastating crop and financial losses in Oregon’s hazelnut industry. By assisting farmers, we additionally help strengthen and grow the industry and reduce negative impacts on the environment. We will accomplish this by conducting research on borer biology and phenology, monitoring, and plant protection. The research will form the basis for Extension resources provided to the industry.

Research objectives:

1. Develop phenology data for PFB. There is no information on when PFB emerge and attack trees. These data act as the foundation for pest management; identifying when PFB life stages vulnerable to management are active.
2. Develop PFB monitoring traps. There are no effective monitoring tools to identify PFB populations. The development of monitoring traps will improve application timing and limit unnecessary pesticide applications when population counts are below economical thresholds.
3. Evaluate plant protection strategies against PFB. We will evaluate simple physical trunk barriers, deterrents, systemic insecticides, organic, and reduced-risk insecticides as treatments. Grower implementation of efficient protection strategies will lower farmer cost and limit environmental contamination.