The two major mite pests of apples in Ontario are the European red mite, Panonychus ulmi (Koch), and the twospotted spider mite, Tetranychus urticae (Koch). Both species belong to the phytophagous (plant feeding) mite family Tetranychidae, or spider mites, and are pests of many crops including tree fruit, small fruit, vegetable, ornamental and field crops. The apple rust mite, Aculus schlechtendali (Nalepa), is a sporadic pest belonging to the mite family Eriophyidae.

Apple rust mites seldom cause a measurable loss in apple orchards. There are exceptions and miticides are sometimes needed for management of populations. Twospotted spider mites tend to be more of a problem in eastern Ontario than southwestern Ontario. Growing season temperature is the most important abiotic factor affecting population buildup. The development of mites is positively correlated to temperature – the warmer the temperature, the faster mites hatch, mature and reproduce. Both European red mite and twospotted spider mite do best under hot, dry conditions.