bacterial blight of hazelnut

Symptoms

Angular brown leaf spots with yellow halos, dark sunken cankers on twigs + young branches with bacterial ooze in spring, branch dieback + tip flagging, dark spots on developing nut husks sometimes penetrating kernels, young nursery trees can be killed outright in heavy infections.

Plants affected

• European hazelnut

Easily confused with

• eastern filbert blight

  How to tell them apart: Eastern filbert blight (a fungus). Look for elongated, sunken cankers along branches and stems that carry rows of distinctive black, rough, football-shaped (oval) erumpent stromata bursting in lines through the bark — this is the decisive sign. Cankers expand year over year and girdle limbs, killing whole branches above them; foliage on affected limbs wilts and dies back. The black stromatic rows are absent in bacterial blight and are diagnostic for EFB. Bacterial blight (a bacterium). Look for small angular brown-to-black leaf spots, often with a yellow halo and confined by leaf veins, plus dark water-soaked sunken lesions on green shoots, petioles and buds; infected buds turn brown and fail to open. Twig and shoot lesions are smooth and dark without any raised black stromata, and damage is worst in cool wet spring weather. The absence of erumpent black football-shaped fruiting bodies separates it from EFB.

Common questions

How do I recognise bacterial blight of hazelnut on European hazelnut?

Angular brown leaf spots with yellow halos, dark sunken cankers on twigs + young branches with bacterial ooze in spring, branch dieback + tip flagging, dark spots on developing nut husks sometimes penetrating kernels, young nursery trees can be killed outright in heavy infections.

Do I have to report bacterial blight of hazelnut?

No. bacterial blight of hazelnut is not a notifiable organism, so there is nothing to report to an authority. Treat it as a normal garden problem.

How is bacterial blight of hazelnut treated?

Mainly with biological and cultural measures — removing affected material, changing the conditions that favour it, and treating with agents approved in your country. The exact steps and their timing depend on the plant, the season and where you live: Dr. Phyto works them out in a free diagnosis.