European red mite, Panonychus ulmi, was first identified in Western Australian apple orchards in 2005 and is now present in all major fruit gowing regions here. It has been present in eastern Australia since at least 1954.
It is found in virtually all of the world’s apple production regions and its presence does not restrict exports.
Only the colder regions in Western Australia (WA) such as Bridgetown to Pemberton seem to provide suitable conditions for consistently damaging populations. European red mite may have been present in WA for some time but sprays against two-spotted mite,Tetranychus urticae, lack of sufficient winter chill for overwintering egg survival and some activity of generalist predators, may help keep populations below significant levels.
Distribution, hosts, damage
European red mite is primarily a pest of deciduous fruit trees. The main fruit affected is the apple. Pears and plums are also hosts but less likely to be damaged. Some varieties have greater susceptibility, for example, Hi-early apples and Wilson plums.
Minor hosts include almond, cedars, citrus, cherry, coffee, cotton, grapevine, peanut and some ornamental trees and shrubs, especially in the Rosaceae family such as roses.
European red mite feeding results in leaf mottling on the upper surface of leaves. This may be confused with similar mottling suspected to be caused by an infection with a mild strain of virus, but the mottling by the virus is bright yellow with large patches often present.
Heavy infestations result in leaf bronzing and premature leaf fall. Prolonged feeding can result in reduced fruit size and colour, and may affect fruit set the following season.
European red mite eggs are red or orange, globular and slightly flattened on top. Each egg looks like an onion, with a white stalk at the top as long as the egg is wide. Bryobia mite eggs are also red but lack the spike.
Eggs of the other common pest mite that occurs in orchards, two-spotted mite, are spherical and yellow (see below). Eggs of these mites are about the same size.
From autumn onwards, adult European red mite adults lay batches of eggs in protected situations on the trunks of trees and the calyx end of apples. Because such large numbers are often laid in one location, they are relatively easily seen. European red mite overwinters on host plants in the egg stage.
The immature stage of European red mite is red to orange or green with six (larva) or eight (nymph) legs.
The red to maroon adult European red mite female is very distinctive, with four rows of small white spots on the back, from which strong spines protrude. It is globular in shape and usually slightly smaller at 0.3‑0.4mm long in comparison to two-spotted mite, the other common pest mite found in orchards.
Female two-spotted mites are 0.4‑0.5mm long and have two dark patches on each side of the body.
Adult male European red mites are pear-shaped and about a quarter of the size of females, with relatively longer legs and a tapered abdomen. Males are straw-coloured, with a light red or green tint.