In this section:
Two Spotted Mite
Tetranychus urticae
Affected
Stone and pome fruit.
Description
The active feeding adult mite is about 0.4 mm long, has eight legs and is pale green in colour. When the larva hatch they have six legs. Both the larva and feeding adult have dark spots on each side of the body. The over-wintering non-feeding female is a distinctive bright orange-red colour without the dark spots.
Where and when to look
Two spotted mites may infest trees from November to March. Look for mites on the underleaf surfaces in the lower inner parts of the tree where infestation begins. Use a hand lens or magnifying glass as the mites are difficult to detect with the naked eye.
Build-up of mite numbers is favoured by hot (25-30° C) dry weather. High humidity and rain will reduce mite numbers. Two spotted mite infestation tends to be more severe in vigorous healthy trees.
Damage
Adult and immature mites suck the contents from leaf cells. Lightly infested leaves have pale spots which give the leaf a speckled appearance. More intense infestations cause bronzing or yellowing of the leaves which prematurely drop.
Control
Two spotted mite has developed resistance to many miticides which once effectively controlled it. Remaining miticides should be used discerningly so as to minimise the build-up of resistance in the mite population to them. Sprays should not be applied at the first sign of mites, but only when numbers reach a critical level, and insufficient numbers of predatory mites exist in the orchard to bring them under control. A monitoring program for the pest and its predators will assist in achieving responsible cost effective control of the pest mites.
Where control of two spotted mites is being based on predators, it is advisable to employ a pest monitoring service (at least in the first few years). Growers who wish to perform their own monitoring need to obtain information on mite identification, scouting, decision making criteria and toxicity to predators of the various agricultural chemicals used in orchards.
Problems in apricots occur mainly as a result of insecticide sprays killing the two spotted mites natural enemies (predators). Where insecticide sprays are not applied in an orchard, mite numbers rarely build-up to a level which warrants the application of a miticide. Avoidance of insecticide sprays by the use of pheromone ties for the control of oriental fruit moth and control of light brown apple moth with the biological agent Bacillus thuringiensis if an outbreak occurs can assist in maintaining predator numbers.
