Several species of mite are important pests of cane fruit and some are very important predator species that are integral part of biological management of mites and other insects. The most important species, both in open-field and in semi-protected cane fruit is the two-spotted spider mite (Tetranychus urticae). Another group of increasingly important mites are the Eriophyid mites. Members of this group, the raspberry leaf and bud mite (Phyllocoptes gracilis) attack raspberry and some hybrid berries and the blackberry mite (Acalitus essigi) damages blackberries.
Image on left is a raspberry primocane damaged by a high density of raspberry leaf and bud mites.
The raspberry leaf and bud mite (image to right shows part of an overwintered colony with the outer bud scales removed) has recently increased in importance as raspberry production has moved to protected and semi-protected cultivation. Much of the detailed studies of these mites were done at SCRI in the early 1970s and the main factors in expression of mite damage are the cultivar grown and whether the site is sheltered. Observations have shown that there appears to be considerable variation in cultivar susceptibility. Of the current cultivars grown under protected cultivation, Glen Ample is particularly susceptible. Other newer cultivars have been reported as causing damage, but as yet, these have not been substantiated. The research of the 1970s showed that mites were most numerous in sheltered environments, such as, behind belts of trees or other windbreaks and in hollows in fields. The specific reason for sheltered sites favouring mite build up is not known, but may be related to increased deposition of these minute mites from air stream as the airflow decreases in the eddies behind the shelter, or by reduced migration from the sites due to reduction in air-flow or changes to the environmental conditions due to the shelter.
In the past, control was achieved by use of broad spectrum acaricides or by one specific systemic insecticide, but these products has been withdrawn from use and no alternative approved product is available. It was thought that the naturally occurring mite, Typhlodromus pyri, was involved in maintaining the raspberry leaf and bud mites in check after application of the insecticide.
Research funded by Horticultural Development Council (HDC) has begun to manage the raspberry leaf and bud mite in raspberries. This research is aimed at understanding the effect of current and newer pesticides and predatory mites on raspberry leaf and bud mite in commercial plantation and in the laboratory.
Photograph to left shows a scanning electron microscope image of raspberry leaf and bud mite.
Gordon SC & Taylor CE (1976) Some aspects of the biology of the raspberry leaf and bud mite (Phyllocoptes (Eriophyes) gracilis Nal.) Eriophyidae in Scotland. Journal of Horticultural Science. 51, 501-508.
Gordon SC & Taylor CE (1977) Chemical control of the raspberry leaf and bud mite, Phyllocoptes gracilis (Nal.) (Eriophyidae). Journal of Horticultural Science 52, 517-523.
Tuovinen T, Lindqvist I, Grassi A, Zini M, Höhn H, Schmid K, Gordon SC & Woodford JAT (2000) The role of native and introduced predatory mites in management of spider mites in Finland, Italy and Switzerland. Proceedings of BCPC Conference-Pests & Diseases 2000. 333-338.