Raspberry cane midge (Resseliella theobaldi (Barnes)) : biology, control methods and monitoring

Abstract: Raspberry cane midge is a serious pest of raspberries. The larvae feed in natural splits in the primocanes and these feeding wounds allow entry of infection by several fungi. The complex of larval feeding and fungal infection is termed midge blight. Midge blight leads to poor vigour of second-year canes with fewer fruit-bearing lateral shoots. Efficient control is difficult to achieve due to the sheltered place where the larval feeding and the short lifespan of adults. Monitoring of the male flight period is possible with sex pheromone traps. This thesis includes trials conducted in the season of 2007 in a raspberry plantation situated in the south of Sweden. In 2006, the presence of the raspberry cane midge in the plantation was confirmed by large catches in the pheromone. The trials in 2007 included two pheromone traps that were deployed for monitoring of male midges in an unsprayed row of the raspberry cultivar Tulameen. In the same row the presence of larvae and eggs in primocanes were studied by making artificial splits, in which female midges laid their eggs. The results from the pheromone traps showed flight of male midges from late April until the beginning of October. The highest trap catches were recorded from the middle of July to late August with peak trap catches of 400-500 male midges per trap and week. The highest number of eggs and larvae in the artificial splits were found in July with 12 eggs and larvae per cm split. The increase of male midges trapped in pheromone traps in August was not followed by higher number of larvae and eggs in splits. This is results could be due to the presence of more natural splits later in the season leading to a dilution effect. Also predation of anthocorid bugs and predatory gall midges could have decreased populations of larvae in splits. An additional study was conducted to investigate possible interference between pheromone traps. The results indicate that traps placed in close vicinity (7 and 20 metres apart) show a decrease in number of trapped midges, thus monitoring traps should be placed more than 20 metres apart to give representative data of the male flight pattern.