Resseliella theobaldi Barnes Raspberry cane midge

The raspberry cane midge is a widespread and locally important pest of raspberry, particularly in the main raspberry-growing areas of England and Scotland. Occasionally, attacks also occur on loganberry. The larvae may be found beneath the rind of the new canes, immediately adjacent to growth splits. The feeding sites eventually turn brown or black but direct damage is usually of only minor importance. More significantly, midge-damaged canes are often infected by fungal pathogens; this results in a disease known as 'midge blight', and this may lead to the death of canes ('cane blight'). Midge damage is especially severe on cultivars with freely splitting canes (e.g. Glen Clova, Mailing Enterprise and Mailing Promise) and, where 'midge blight' develops, crop yields in the following season may be reduced considerably.

BIOLOGY

Adult midges appear from early May onwards but the time of appearance varies by several days to a few weeks, depending on local temperatures. Eggs are deposited in breaks in new raspberry canes and hatch in about a week. The larvae feed gregariously beneath the rind for up to 3 weeks and then drop to the ground to spin silken cocoons in the soil. Second-generation adults emerge 2-3 weeks later. There are usually three overlapping generations each year and larval populations tend to increase markedly as the season progresses; in late summer and autumn, there may be several hundred larvae feeding on any one infested cane. Fully grown larvae of the autumn generation overwinter in their cocoons and pupate in the spring.

DESCRIPTION

Adult 2.0 mm long, dark reddish-brown. Egg minute, sausage-shaped, translucent. Larva up to 3.5 mm long, translucent when young but soon becoming yellowish-orange to salmon-pink.

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