Botryosphaeria Leaf Spot of Mamaki (Pipturus albidus)

Mamaki [Pipturus albidus (=P. hawaiiensis)] is an endemic shrub or small tree (2-6 m tall) of the Urticaceae family.  It is scattered to locally common in mesic to wet forests over a wide elevational range (70-1,870 m) on most of the main islands of Hawai‘i.  The species is characterized by the presence of long, strong bark fibers that were used in Hawaiian culture for cordage and for making tapa cloth.  The bark, fruit, and young leaves also were used medicinally.

We reported a leaf spot disease, caused by the newly described species Botryosphaeria pipturi, found frequently in the Kipuka Puaulu region of Hawai‘i Volcanoes National Park (Gardner and Hodges, 1988).  The spots are black when fresh, epiphyllous, circular, raised, 4-15 mm in diameter and later appear as grayish-white necrotic areas with several erumpent black ascostromata near the center.  Morphological characteristics of the ascostromata and conidiomata are described in more detail in the above citation.  Whereas pathogenic members of the widespread genus Botryosphaeria are usually associated with bark cankers and branch and twig dieback of woody hosts, newly described

   Fresh leaf spots caused by Botryosphaeria pipturi on mamaki.

      Leaf tissue of older infections become crusty and puckered.  The leaf spots take on a whitish-gray appearance with the dark stromata visible as dot-like structures

   Section through an ascostroma showing a locule containing asci with ascospores.