A bud is a small, undeveloped shoot that contains the potential for new growth. Buds are typically found on stems, where they can be apical (found at the tip) or axillary (found between leaf axils) and may develop into leaves, shoots or flowers.

bud

This mite is one of the gall mites, also known as eriophyid mites, are minute animals usually less than 0.2mm long when fully grown. They have elongate bodies and two pairs of legs, unlike other mites which have four pairs. Their size means they can usually only be seen with the aid of a microscope. Their presence is readily detected by the distinctive abnormal plant growths induced by their feeding activities.

There are many species of eriophyid mite which are usually host specific this means that each species of mite will only feed on a single, or several closely related, plant species.

Eriophyid mites feed by sucking

Sap is a fluid that circulates through a plant's vascular system, in a similar way to blood moving through our veins. Phloem sap carries the sugars produced in the leaves by photosynthesis down to roots and other storage organs, as well as carrying minerals and hormones. Xylem sap is watery and transports nutrients absorbed by the roots upwards to the rest of the plant. Some plants leak sap from wounds or pruning cuts, and this is known as bleeding.

Meristem is a type of tissue that is responsible for growth and development in plants. It consists of unspecialised cells that can divide and diversify into various types of specialised cells. Meristems are only found in certain parts of a plant, such as at root and shoot tips and in bundles between xylem and phloem vessels.

meristem

Raspberries with leaf and but mite show a number of symptoms;

• From May onwards, pale yellow blotches develop on the upper leaf surface
• On the corresponding places on the underside of leaves, the colour is slightly darker than the usual whitish green
• Affected canes grow to their usual height and produce fruit but leaves at the tops of the canes may be malformed

Note: Some virus infections also cause yellow markings on the foliage, usually accompanied with stunting of the canes and poor fruit production. The mite is a more common problem than virus infections although it can transmit Raspberry leaf blotch virus.

• Raspberry leaf and bud mite can often be tolerated as it does not always affect cropping
• Heavily affected plants that no longer produce a worthwhile crop should be replaced
• Some raspberry cultivars are less susceptible to the mite. Observations on plants grown at Wisley indicate that these include ‘Glen Lyon’, ‘Glen Rosa’, ‘Glen Prosen’, ‘Glen Magna’, ‘Malahat’, ‘Gala’, ‘Tulameen’, ‘Julia’, ‘Rossana’, ‘Leo’, ‘Galante’, ‘Terrie Louise’ and ‘Lauren’
• More susceptible cultivars include ‘Glen Ample’, ‘Glen Shee’, ‘Malling Jewel’ and ‘Malling Enterprise’
• None of the pesticides available to home gardeners will control this mite.

The microscopic raspberry leaf and bud mites overwinter in and around the buds on raspberry canes.

They emerge in late spring and begin feeding by sucking sap from the underside of leaves. This results in yellow blotches developing on the upper surface and slightly darker patches on the lower leaf surface where the mites are active.

The mite population increases during the summer and leaves at the shoot tops may fail to expand to their usual size and shape if the population of mites is large.