Common Midwest Oak Tree Diseases: Botryosphaeria Twig Canker

Botryosphaeria Twig Canker Botryosphaeria twig canker is a disease that affects red and white oaks. Properly caring for your trees, keeping landscaping tools and equipment clean, and watching out for signs of lesions on leaves can help you avoid this common oak tree disease.

What Causes Botryosphaeria Twig Canker?

A fungus is the cause of Botryosphaeria twig canker. As its name suggests, the specific fungus identified for this disease is Botryosphaeria spp. Symptoms of this disease typically present in the mid-summer, after periods of heavy spring rainfall, and dead branch tips may remain visible through the fall.

Signs of Botryosphaeria Twig Canker

When the fungus attacks a tree, it causes brown, wilted leaves on the tips of tree branches, extending 4-6 inches in from branch tips. Upon closer inspection, you will see brownish-black elongated lesions (cankers) on affected limbs. Within the lesions, black, pimple-like fruiting structures also develop.

The infection is random and scattered, effecting the outermost branches rather than the whole limb. Botryosphaeria twig canker impairs the phloem and cambium tissue, inhibiting the proper flow of water and nutrients and causing leaf structure beyond the cankers to turn brown and wilt. Sapwood discoloration may also occur.

Note: Cicada and twig-pruner insect damage can present similar dieback symptoms. 

Long-Term Effects 

Dieback with this disease is typically minimal, inflicting little damage to the overall tree health.

Treatment Options 

Botryosphaeria fungus overwinters on fruiting bodies and dead tissue, making timely, careful pruning essential. Prune affected trees in the winter when trees are dormant, removing infected twigs and branches and destroying them. Carefully clean all pruning tools following removal to prevent the spread of the fungus, which is disseminated via contact or air movement/splash dispersal of spores. Chemical controls are not typically warranted, as there are currently no effective fungicidal controls for Botryosphaeria twig canker.

Wounded plant tissue makes trees particularly susceptible to infection by Botryosphaeria spp. Using proper pruning techniques and carefully planting/transplanting your oak trees with the help of your ProLine Grabber and Forques can significantly reduce the risk of a Botryosphaeria infection.

Tips for Avoiding Botryosphaeria Twig Canker

This fungus is an opportunistic pathogen, causing disease only on plants that are stressed. Avoiding stressors is key to preventing infection and colonization. This can be accomplished by:

  • Developing trees with large healthy crowns.
  • Ensuring adequate (but not excessive) watering and proper aeration.
  • Avoiding the thinning of trees during drought or insect infestation.
  • Properly cleaning tools after every pruning session.
  • Diversifying the age classes of your trees.

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