Several arthropod pests feed on hazelnut foliage and damage nuts. Our lab is studying management options for several of these pests.

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Pacific flatheaded borer (Chrysobothris mali) is a beetle that damages stressed young trees. Borer damage can be avoided by reducing plant stress through adequate irrigation, preventing sunburn by painting trunks with a 50/50 mixture of white latex paint and water. Maintaining balanced nutrient levels is also key to healthy trees.

Shot hole borers are small black beetles, which bore into trees and create multiple galleries radiating out from the center of the trunk.

Ambrosia beetles cause damage by inoculating trees with a fungus, which adult beetles maintain for feeding their developing offspring. The beetles can persist in the trees for multiple generations.

The lab is currently studying development of Pacific flatheaded borer, emergence from overwintering sites, and insecticide management options for combating these pests and increasing tree longevity.

Bud mites

These pests feed on developing buds and prevent nut development. Since most of their life cycle is spent protected within developing buds, they are difficult to manage. Timing of pesticide applications is critical to manage bud mites, since they must be sprayed when exposed. Mites can be monitored using double sided sticky tape, and this information can be used to determine when management will be most effective. The lab is monitoring population movement in the Willamette Valley and testing pesticide options that might be less damaging to natural enemies.


Filbertworm (FBW), a (Cydia latiferreana) a moth native to North America, is especially challenging to manage. This insect overwinters as a larva in leaf debris. Adults emerge from June – October and lay eggs singly near maturing nuts. After hatching, the larvae bore into acorns and hazelnuts.

Filbertworm movement into orchards

Adult (Credit: Seth Ausubel)

Since FBW feed on both nut species, prophylactic insecticide treatments to oak trees surrounding their hazelnut orchards may prevent FBW migration into into the orchards.  Yet, there is scant evidence to support this management recommendation. Therefore, we are initiating a trial to study the movement of FBW in and around hazelnut orchards.

We are raising FBW on acorns and hazelnuts and will analyze  if there are distinct differences between adult moth lipid (fat) composition.  If differences exist between the lipids of FBW fed different diets, we will monitor for FBW in hazelnut orchards during the summer of 2017, process adults captured in traps, and identify if the moths contain the specific lipids found in FBW that fed upon acorns.  If they do, it can be presumed that, in some situations, FBW are migrating from oak trees into hazelnut orchards, and that management of nearby oaks could be substantiated if the orchard has a severe FBW problem.

Signs of Filbertworm damage

PNW guide to managing filbertworm

Additional resources

Resources on pests of hazelnut

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