The Bryobia Mite and the Pear-leaf Blister Mite
Note Number: AG0094
Published: June 2000
Updated: February 2010
The bryobia mite (Bryobia rubrioculus)
The egg of the Bryobia mite is minute, globular and red. It can be distinguished from European red mite eggs by its smooth appearance and lack of a spike. The nymph looks like the adult but is smaller. The adult is about 0.7 mm long and is purplish brown, with eight legs, the front pair of which is extremely long.
Bryobia mite attacks a range of fruit trees but is most common on almonds. The adult damages the leaves of plants by sucking sap. Leaves which are heavily infested with mites become pale and may prematurely fall. Bryobia mite has become a pest on pears since the fruit industry has dramatically reduced its pesticide usage.
The bryobia mite overwinters in the egg stage on the bark of branches and twigs. The number of overwintering eggs is sometimes so great that parts of the bark have a reddish tinge. The young mites hatch in spring and feed on the leaves of fruit trees. There are several broods of mites in Victoria in a season before the overwintering eggs are laid.
A spray of winter oil usually controls bryobia mite satisfactorily. There are a number of predatory insects and mites which eat Bryobia mite. These beneficial species are often killed by inappropriate use of pesticides. Local horticultural advisers should be able to provide advice on selection of pesticides safe to these species.
The pear-leaf blister mite (Eriophyes pyri)
The adult is minute, whitish or pinkish, and has an elongated, tapering, ringed abdomen and only two pairs of legs located near the head. It is difficult to see at 10 x magnification and you may require a microscope to detect this pest.
The adult mite attacks pear trees, damaging leaves by sucking sap and forming blisters. The mites also attack the fruit, where they cause depressed, russeted spots, with dwarfing and malformation in severe infestations.
The adult mites overwinter in bud scales. In warm areas, the eggs may be laid in the scales and develop there. The eggs normally hatch in spring and the mites start to feed on the undersides of new leaves, where they cause the formation of blisters in which the eggs are laid. The colonies of young mites feed on the plant tissue entirely within the blister. They are almost completely protected, although they may move in and out through a small central opening. A number of generations develop on the leaves. Activity may decrease in the hot summer months, but fresh blisters are often produced on late summer growth.
These pests are rarely a problem in modern commercial orchards. Consult your local horticulturalist or the current edition of the Orchard Pest and Disease Handbook.
Contact the Customer Service Centre of the Department of Primary Industries, Victoria at 136 186.
For information relating to the safe and appropriate use of chemicals, including management of chemical residues and licensing requirements, call the DPI Customer Service Centre of 138 186 and ask to speak to your local chemical standards officer or visit www.dpi.vic.gov.au/chemicalstandards.
This Agnote was developed by David Williams, Future Farming Systems Research, Victoria, June 2000.
It was reviewed by Harold Adem, Farm Services Victoria, February 2010.
Published and Authorised by:
Department of Environment and Primary Industries
1 Spring Street
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