PEST

NAME
Mites (General)
Various Species

ORDER
Acarina

FAMILY
Aleyrodidae


Description of the Pest
Generally mites attack the plant by sucking the sap from leaves and in some cases cause galls on the leaf surface or in the flower and on the fruit. The Adult body is composed of two parts, a head-thorax combination and an abdomen, both fused together to appear as a single segment. The size varies but generally they are small pear-shaped animals that are 1mm or less and have no antennae or wings.

The females have eight legs and vary in colour depending on the host plant and the nymphs are six-legged, with another pair of legs appearing as the mite matures. Males are generally smaller and fully-grown adults of some species are visible to the naked eye.

Bulb Mite(Rhizoglyphus echinopus). This is a slow moving yellowish-white mite may be visible to the naked eye and infests bulbs or corms in the soil. When lifted under warm humid conditions of 16şC (61şF) and above the mites are most active causing bulbs to deteriorate quickly. Under cool conditions the mites may go undetected and when replanted they cause the leaves to turn yellow and the flower to blight. On inspection of the bulb the scales are hard with a brownish colour and the dried pulp will be infested with hundreds of active mites. This damage allows the entry of other fungal or bacterial rots to occur.

Eucalyptus Blister Gallis a rough textured gall that appears on the leaf surface as a pale coloured raised area and may be blotched with red. The tiny mites that cause this damage feed breed and live within the gall causing extensive disfiguring of the leaves in certain tree species. There are a variety of species that attack such as Eriophyid mite and occur from tropical to temperate regions and normally found on Eucalyptus.

     

Appearance and Distribution of the Pest
Found world-wide with over 30,000 species. They congregate in protected places, such as under bark and at the base of trees, during winter.

Life Cycle
Mites have a gradual metamorphosis, with several nymphal stages. Each female lays up to 100 eggs that hatch in 7-14 days, with several generations appearing throughout the year. Females may become inactive during cold weather.

Period of Activity
Mites are most active during the warmer months of the year, preferring drier periods.

Damage Caused
Normally Gall Mites do not cause significant damage although they may interfere with flower and fruit production. Certain species such as Banksia integrifoliaare more susceptible than other plants.

Susceptible Plants
A wide range of plants are attacked by Mites including annuals, fruit trees and vegetables, ornamental shrubs and trees.

Banksia integrifolia is attacked by the Banksia Mite Gallwhich disfigures developing fruit, reducing the quantity of seed produced.

Banksia integrifolia

Sorbus aucupariais attacked by the Pear Leaf Blister Mite(Eriophyes pyri) infests leaves causing blisters on the underside of the leaf and eventual defoliating of the tree.

Tulipaand Crocusspecies are attacked by Bulb Mite(Rhizoglyphus echinopus) causing the bulbs or corms to deteriorate.

Note
Many plant species are more susceptible to Red Spider Mitewhen they are cultivated under glass.

Cultural Control
Heavy rain or irrigation can reduce numbers as will frequent overhead watering; some plants may benefit from replanting in cooler locations. Generally, however, infested material should be completely removed and destroyed. Preventive measures include weed control and removal and destruction of plant material that is infested. Galls that appear on plants should be removed to reduce population build up and plants that are repetitively attacked should be replaced with less susceptible species.
Plants that are infected with Bulb Mite can have the bulbs or corms (before they develop roots) dipped into hot water for a few minutes to eradicate the pest. Soil that is infested needs to be steam-pasteurised prior to replanting.

BiologicalControl
Natural predators include lacewings, ladybirds and thrips; insecticide-resistant predatory mites are also available commercially to control the Two-spotted Mite such as Phytoseiulus persimilis.

Chemical Control
Dimethoate will reduce numbers; however, mites become resistant to insecticides. Dusting with wettable sulphur may also prove effective.