Botryosphaeria obtusa

A fungal pathogen affecting plants

Botryosphaeria obtusa is a fungus that is a known plant pathogen affecting a variety of hosts, including apple and pear trees. It is responsible for diseases such as black rot and frogeye leaf spot.

Morphology

Botryosphaeria obtusa on apple tree

Botryosphaeria obtusa produces pycnidia, which are fruiting bodies that appear as small, black structures on the surface of infected plant tissues. These pycnidia release conidia, which are asexual spores that spread the infection.

Life Cycle

The life cycle of Botryosphaeria obtusa involves both sexual and asexual reproduction. The fungus overwinters in infected plant debris and can produce ascospores in the spring, which are released and spread by wind and rain. The asexual conidia are spread primarily by rain splash.

Symptoms

Infected plants exhibit a range of symptoms, including:

• Black rot on fruit, characterized by dark, sunken lesions.
• Frogeye leaf spot, which appears as small, circular spots with a dark border on leaves.
• Cankers on branches and twigs, leading to dieback.

Management

Management of Botryosphaeria obtusa involves cultural practices and chemical controls. Pruning and removal of infected plant material can reduce the source of inoculum. Fungicides may be applied to protect susceptible plants, especially during wet conditions that favor the spread of the fungus.

Related pages

• Plant pathology
• Fungal diseases of plants
• Apple scab