Gall mite of blackcurrant Cecidophyopsis ribis
Damage. Mites living inside the blackcurrant bud damage the meristem and induce the bud to produce many scale leaves, which gives the bud its unusual swollen appearance (see Figure 14.26). These buds either fail to open or produce distorted leaves. In addition to the mechanical damage, the mite carries the virus responsible for reversion disease (see Chapter 15), which stunts the plant and reduces fruit production.
- Figure 14.26 (a) Big bud symptoms on blackcurrant (b) Erineum mite damage on grape leaf
Life cycle. Unlike red spider mite, this species, sometimes called big-bud mite, is elongated in shape and is minute (0.25 mm) in size. It spends most of the year living inside the buds of blackcurrants and, to a lesser extent, other Ribes species. Breeding takes place inside the buds from June to September, and January to April.
- In May the mites emerge and are spread on silk threads and on the bodies of aphids to infest newly emerging buds and plants.
- The mite is controlled in three ways. Clean planting material is essential for the establishment of a healthy crop. Pruning out of stems with big bud and destruction of reversion-infected plants slows down the progress of the pest. Amateur gardeners and professional growers can spray a fine formulation of sulphur during the May-June period when the mites are migrating. There are no chemical ways to control the mite in the bud. Recently there has been a reported problem on hazel in UK caused by the hazel big bud mite (Phytopus avellanae).
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