8

Scab and Fire Blight of Apple: Issues

in Integrated Pest Management

Janna L. Beckerman
Department of Botany and Plant Pathology,
Purdue University, West Lafayette, IN, USA

George W. Sundin
Department of Plant, Soil, and Microbial Sciences,
Michigan State University, East Lansing, MI, USA

ABSTRACT

More than 100 pathogens infect apples (Sutton et al. 2014) but two diseases,
apple scab and fire blight, have been particularly important and resulted in
worldwide problems for disease management, especially in humid climates.
This review focuses on apple scab, caused by the fungusVenturia inaequalis
(Cke.) Wint., and fire blight, caused by the bacteriumErwinia amylovora
(Burrill). Apple scab is one of the most destructive fungal diseases of apples in
the midwest and northeastern United States (MacHardy 1996), necessitating 12–
20 applications of fungicides per season for commercially acceptable control.
Fire blight, or the threat of this disease, is a major limiting factor to orchard sus-
tainability in most regions where apple trees are grown. In the absence of proper
management, both pathogens will quickly spread through a typical commercial
orchard. Apple scab can cause 100% crop loss and defoliation so severe as to
impact the next year’s crop. Fire blight is capable of killing trees quickly and de-
stroying entire orchards, particularly in typical modern high-density orchards.
We will discuss the development of control measures for these two distinct dis-
eases, problems associated with fungicide and bactericide resistance, and how
some solutions to issues with one disease affected the successful management
of the other.

Horticultural Reviews, Volume 44, First Edition. Edited by Jules Janick.
© 2017 Wiley-Blackwell. Published 2017 by John Wiley & Sons, Inc.

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