Filbert Big Bud Mite
Phytoptus avellanae and Cecidophyopsis vermiformis
Microscopic eriophyid mites that live inside hazelnut (filbert) buds and make them swell into enlarged, rounded big buds that fail to leaf out or flower. They are among the most important pests of hazelnut, sapping the tree of its fruiting wood.
🔎 How to spot it
The mites themselves are far too small to see without magnification, so the sign is the buds: infested buds swell to several times normal size into round, loose, scaly big buds that stand out over winter and early spring, in contrast to the slim, pointed healthy buds. Affected buds blast (die) or, if they open, produce stunted, distorted shoots.
🥀 Damage it causes
Infested buds enlarge and then fail, dying without leafing out or flowering, or producing weak, deformed growth. This destroys fruiting and vegetative buds and reduces the tree bearing wood; up to about 30 percent of buds can be infested on susceptible varieties, cutting into the crop.
🛡️ Prevent it
Plant resistant cultivars where bud mites are a known problem, since hazelnut varieties differ widely in susceptibility and breeding programs select against the mite. On a small scale, pick off and destroy the swollen big buds in late winter before the mites move out, and avoid bringing in infested nursery stock.
🧯 If it is already here
Timing is everything because the mites are shielded inside the buds most of the year; the window is when nymphs migrate from the old blasted buds to the new buds, roughly early spring as buds form. Sulfur or lime-sulfur and miticides applied at that peak-migration timing give the best control, and predatory mites help keep numbers down.
💡 Good to know
The loose, rounded big buds are easy to spot against the slim normal buds once you know to look in late winter. Because the mites hide inside the buds, sprays only work during the brief spring migration, so resistant varieties are the most reliable long-term answer.
🌱 Plants it attacks
3 plants in the library can be attacked by this pest
For educational and informational purposes only. Pest control advice is general guidance drawn from university cooperative extension sources; always identify a pest positively and read and follow the label on any product before use, especially around food crops, children, and pets.