The Biology of Malus domestica Borkh. (Apple)
6. Potential Interaction of Malus domestica with Other Life Forms

M. domestica is susceptible to a number of plant diseases and insect pests. The most economically important disease of apples in North America is apple scab (Jones and Aldwinckle 1990) caused by the fungal pathogen, Venturia inaequalis (Cooke) Wint. Apple scab is reported as having widespread yearly occurrence with high pest pressure in all major apple production regions within Canada (AAFC 2011; BCMA 2012). Another significant disease reported as having widespread yearly occurrence with high pest pressure (in Ontario) is fireblight caused by the bacterium Erwinia amylovora (Burrill) Winslow et al., which can, under the right conditions, wipe out entire orchards within a growing season (AAFC 2011). Other significant diseases reported as having localized yearly occurrence with high pest pressure or widespread sporadic occurrence with high pest pressure in Canada include black rot (in Ontario), caused by the fungal pathogen Botryosphaeria obtusa (Schwein.) Shoemaker, powdery mildew (in Ontario and British Columbia), caused by the fungal pathogen Podosphaera leucotricha (Ellis & Everh.) E.S. Salmon, replant disease complex (in Nova Scotia, Quebec and British Columbia), a combination of fungal and bacterial soilborne organisms, as well as nematodes, which affects newly planted apples in locations previously planted as apple orchards (AAFC 2011).

Apple maggot, Rhagoletis pomonella (Walsh) and codling moth, Cydia pomonella (L.) are serious insect pests for apple each with the potential to cause 100% yield loss and are both reported as having widespread yearly occurrence with high pest pressure for eastern Canadian apple producing regions (Nova Scotia, Quebec and Ontario) (AAFC 2011). Other significant insect pests reported as having widespread yearly occurrence across the major apple producing regions in Canada include: plum curculio, Conotrachelus nenuphar (Herbst) in Ontario and Quebec, oblique banded leaf roller, Choristoneura rosaceana (Harris) in British Columbia, Ontario and Quebec, three lined leaf roller, Pandemis limitata (Robinson), fruit tree leaf-roller, Archips argyrospila (Walker), European red mite, Panonychus ulmi (Koch) and two-spotted spider mite, Tetranychus urticae (C.L.Koch) in Quebec and mullein plant bug, Campylomma verbasci (Meyer-Dür) in British Columbia (AAFC 2011). Chemical, biological and cultural control methods are used to limit or eradicate disease and insect pests on apple (AAFC 2011).

Some vertebrates can also be considered pests to apple growers. Birds can become a nuisance by pecking holes in the fruit or wood (AAFC 2011). Various mammals, including rodents, rabbits and deer have been associated with various damage to tree tissues including girdling of bark and feeding on young branches, leaves and buds (AAFC 2011). Bears will also eat the fruit and can damage trees in doing so.

For a list of species associated with M. domestica, please refer to Table 4.

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