Shot Hole

Pest: Shot hole, Coryneum blight (Wilsonomyces carpophilus)

Pest Type: Infectious disease, fungus

Major Identifying Features: Shot hole can be seen first in spring as purplish or reddish spots on new buds, leaves, shoots, spots expand and their centers turn brown and can drop out, leaving holes

Life Cycle: The fungus overwinters in infected buds and twig lesions, spores spread in splashing water, spores need 24 hours of continuous water to cause infection, and only new growth is susceptible to infections

Pest Rating: Moderate

Management Rating: Moderate

Host/Season/Outbreak Information: Hosts include Prunus spp., almonds, Catalina and Japanese flowering cherries, English laurel, ornamental plums, nectarines, peaches, apricots (!), shot hole will develop on cherries, plums, and prunes only when growing near more susceptible hosts when weather is wet, outbreaks are most often in winter or spring after rain

Damage Information: The fungus causes premature leaf drop, rough and corky lesions on fruit that are brown with dark purple margins and mostly on the upper surface, and small cankers on branches, tiny dark specks form in the centers of brown spots (only visible with a hand lens)

Management Options: Cultural control by proper irrigation methods by using drip irrigation, by pruning off lower branches to prevent foliage wetting from irrigation, by pruning infected buds and twigs in fall after leaf drop

Sources:

http://www.ipm.ucanr.edu

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