Raspberry Cane Midge In Organic Fruit

Raspberry cane midge is a widespread and common pest that often causes serious problems in raspberry and also occasionally attacks loganberry. Adult midges are 1.5-2.5mm long and red-green in color. They emerge in early May and lay eggs in the splits on young raspberry canes. Eggs hatch one week later and the larvae feed for two to three weeks in large clusters underneath the cane rind. Larvae are 3-3.5mm long, initially pale in color but later turning salmon-pink, making them visible under the bark of attacked stems. Once mature, they drop to the ground to pupate in red silken cocoons, emerging as adults two to three weeks later. There are usually three generations each year. The larvae of the final September generation over- winter in cocoons in the soil and pupate the following spring.

The main problem is that the midge larvae open up the cane to infection by fungal pathogens such as Did ymella, Fusarium and Leptosphaeria, which cause the disease midge blight, leading to the death of fruiting canes the following year. Midge larvae feeding for several generations may also cause such severe damage to vascular tissue that the affected canes become prone to winter cold injury.

Outdoor cropping, it is most useful near to harvest when field temperatures are more appropriate. Unfortunately, there is no straightforward biological control solution for the large raspberry aphid.

Chemical Control

Pyrethrum, insecticidal soap or natural plant extracts may be used before or after flowering. Their use is best restricted to spot treatments of small colonies early in the season. Sprays applied post-harvest or in the autumn (late September to mid-October) can also give good control, before egg laying commences.