Apple rust mite
(Aculus schlechtendali)

Overview

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The species Aculus schlechtendali is commonly known as the apple rust mite and can be found in all regions of apple production in Canada. 

Main description

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Apple rust mite inserts its mouthparts into plant cells and sucks their liquid contents. This feeding produces a silvery cast to the leaf in the early stages and may result in the leaf rolling up. This type of damage severely disrupts photosynthesis and water intake, resulting in a decrease in fruit size and/or quality. The adult mite can be distinguished through its light tan color; however, they are extremely small and a hand held magnifying glass (of at least 20X) may be required in identification of this pest.

Optimal conditions for infestation

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The development of the apple rust mite is more rapid under conditions of higher temperatures (<22°C) and dryness, to the extent that progression is increased by a factor of three, due to the short life cycle and rapid development of the mite.

Scouting

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Scouting should take place before the petals fall and continue through to early August. A hand held magnifying glass will be required and focus should be placed on the mid-vein-base of leaves. Inspect 10 leaves from 10 different trees in order to get a good diverse reading of the infestation. A quick estimate should be done on numbers due to their small size: when more than 200 mites are found on a leaf then immediate treatment should be considered.