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Southeastern Apple ProductionPLANT PATHOLOGY |
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Black Pox
Helminthosporium papulosum
Black pox, caused by Helminthosporium papulosum, causes fruit spot, leaf spot, and limb and twig canker. Golden Delicious is the most severely affected cultivar grown in the Southeast.
Symptoms
Fruit spots are small (from 1/16 to 1/4 inch in diameter), circular, sunken, and black. Leaf spots are light green with red halos and enlarge to about 1/2 inch in diameter. The center dies and becomes tan. Lesions on stems appear as conical, shiny black swellings.
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| Fruit spots | Fruit spots | Stem lesions |
Disease Cycle
The fungus overwinters in twig and bark cankers. Infections are initiated by conidia produced in these cankers and can occur on fruit as early as May and continue through the summer until harvest.
Control
Control is based on the use of a preventive fungicidal spray program, applied on a 2-week schedule, beginning in mid-May. Pruning to remove water sprouts with cankers will reduce the inoculum and aid in control.
Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by North Carolina Cooperative Extension nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your county Cooperative Extension agent. |
Department of Plant Pathology
North Carolina State University
Raleigh, NC 27695 USA
Web Crafters: Anne S. Napier and
Steve Schoof |
Format updated March 29, 2011