Aphid damage on Brassicaceae

On rape, in the autumn the generalist aphids like the green peach aphid (Myzus persicae) and the black bean aphid (Aphis fabae) can provoke yield losses due to virus transmission. The most widespread virus is the beet western yellow virus (BWYV), transmitted through the persistent mode. The cauliflower mosaic virus (CaMV) and the turnip mosaic virus (TuMV) are less frequent. In spring, the aphids can also cause direct damage if strong outbreaks occur: failure of flowers to develop and leaf scald owing to the cabbage aphid (Brevicoryne brassicae) and leaf deformation due to Myzus persicae and Aphis fabae. In autumn, large colonies of turnip aphids (Lipaphis erysimi) can also jeopardize the plants’ growth.

These kinds of damage can be shown by yield losses of 5-8 q (500-800kg)/ha. The presence of aphids on winter rape will signal the need for close surveillance right from early sprouting. The earliest attacks are the most harmful so rapid action is essential. Treatments using insecticides are advised as soon as two colonies per m² can be seen. These interventions can be limited to affected zones and therefore applied on local areas within the plot. Applications round the edges in particular often help to diminish the attacks.

On cabbage, the cabbage aphids Brevicoryne brassicae is by far the most dangerous species because they are the most difficult to control. On leaves the green peach aphid (Myzus persicae) can also be encountered. The presence of these species induces leaf curl and crinkle, yellowing and withering. These two species are also the principal vectors of two viral diseases: the cauliflower mosaic (CaMV) which is expressed by alternating light and dark spots between veins and the turnip mosaic (TuMV) which induces irregular black spots on leaves. These viruses non circulating and can also be transmitted by other species of aphids.