blueberry stem blight

Symptoms

Sudden wilting + reddening of individual branches in summer, cinnamon-brown bark discoloration extending down from dead tip, dark pycnidia on dead bark, otherwise healthy bush with 1-3 collapsing branches.

Plants affected

• highbush blueberry

Easily confused with

• mummyberry of blueberry

  How to tell them apart: Botryosphaeria dothidea (stem blight) kills whole individual canes that suddenly flag — leaves turn brown/reddish but stay attached — and when you slit the bark you find a sharp wedge-shaped reddish-brown discolouration running down the wood from a wound or pruning cut, usually on older or stressed canes through summer. Monilinia vaccinii-corymbosi (mummy berry) instead strikes the soft new spring growth: young shoots and flower clusters wilt and bend into a brown 'shepherd's crook', the dying tissue often shows a dark central vein, and in humid weather a powdery grey-tan fungal dust (conidia) coats the blighted shoots and later infected fruit shrivel into hard grey 'mummies'. The grey spore mass on collapsed young shoots plus mummified berries is unique to Monilinia; internal wedge-shaped wood streaking on flagging older canes points to Botryosphaeria.

Common questions

How do I recognise blueberry stem blight on highbush blueberry?

Sudden wilting + reddening of individual branches in summer, cinnamon-brown bark discoloration extending down from dead tip, dark pycnidia on dead bark, otherwise healthy bush with 1-3 collapsing branches.

Do I have to report blueberry stem blight?

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

How is blueberry stem blight 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.