Twospotted spider mite - integrated mite control

Integrated mite control (IMC) of twospotted spider mite combines the use of predatory mites (typhs), resistant to orchard chemicals, with the use of selective miticides more toxic to twospotted mite than the predators. IMC was introduced to New Zealand pipfruit orchards in the 1970s. The most important predators are Phytoseiulus persimilis in regions from Nelson northwards, and Galendromus occidentalis in Otago. Both of these typhs have developed resistance to organophosphate (OP) insecticides and are able to provide biological control of twospotted spider mite in the presence of OP sprays. They can be assisted by sprays of selective miticides such as Peropal^®, Torque^® and summer oil. In IMC, these are only applied when spray thresholds are exceeded, as shown by monitoring. Although OP resistance in these predators is less important than it was, due to the introduction of new selective insecticides, IMC continues to this day as an important part of integrated fruit production. Good control of two-spotted mite is usually obtained through the activity of the typhs. However, if twospotted mite is difficult to control, and P. persimilis has not been introduced to the orchard, this predator can be purchased (as 'Mite-E') and introduced upon first sighting twospotted mites on apple foliage (November/December). No further introductions should be required in districts north of Canterbury, but in the south, annual releases may be required. Care is required in the choice of pesticides for compatibility with the predatory mites used in IMC.

Another OP-resistant predator species, Neoseiulus fallacis, was also introduced to New Zealand. It established successfully, particularly in Canterbury and Hawkes Bay, where it was shown to control twospotted spider mites in orchards, but it has since declined. It appears to have been displaced by the larger and more voracious predator, P. persimilis. The predatory ladybird, Stethorus bifidus, is a further predator of twospotted mite which contributes to integrated mite control. The adult beetles are able to locate pockets of twospotted spider mite and reduce the population rapidly. This is particularly seen in late summer.