If you remove some of the outer leaves from the cabbage head, you will be able to find such colonies of cabbage aphids.
Photo: Magnus Gammelgaard
Purple or light sections of cabbage leaves, together with different kinds of leave deformities, are often the result from the presence of cabbage aphids.
If you at the same time are able to find some sticky, shining stuff at the leaves surface, the diagnose normally can be set to be Cabbage aphids.
The honeydew, which the sugary substances are called, is the droppings from the aphids, allows the growth of a black sooty mould. It gives the cabbage an anaesthetic look, especially in Brussels.
The result of a visit from a parasitic wasp is dead aphids.
Photo: Magnus Gammelgaard
The cabbage aphid, over winter primary as eggs, laid by the adult females in the autumn. During mild winters it is normal that the adults are able to over winter and to start a new generation at the next growing season.
The first attack from cabbage aphids are often to be seen at the end of April. If the climate is satisfactory for the development (warm climate), it goes very fast. The females are giving birth to young ones without any fertilization (virgin birth). When the population rise female individuals with wings are born, ready to fly to new hosts.
In late summer/autumn females and males are born, fertilization takes place and the eggs are laid.
Cabbage aphids are only able to feed on crucifers. A heavy waxy layer covers the aphids and protect them from rain (pesticides) and other bad the influences.
Look at evt. Inseckingdom and locate where to find the cabbage aphid.
Cabbage aphids. Look at the individuals with wings who are ready to fly to new hosts.(Brevicoryne brassicae).
Photo:Alton N. Sparks, Jr., The University of Georgia, www.forestryimages.org
Control:The heavy layer of wax makes the aphids very difficult to control.
Luckily there are a lot of natural enemies like ladybugs and parasite wasps. They will, without we have to move a finger, do a considerable cut in the population of aphids (look at earlier pictures of mummies).
Covering the cabbage plants with net can prevent aphid attack if it is done in time. If you are using this procedure you should be aware that the natural enemies also are excluded.
Over wintering cabbage can give the opportunity that the aphids are ready to start up again early in the next growing season.
Yoy can read more about aphids i general on: bladluseng.htm
If You have any further suggestions concerning control matters or aphids in general, I should be very glade to receive those.......
Opdateret d. 19.1.2012