Such swollen formations, called galls, can be found on leaves and petioles of poplars. They contain small aphids. (Pemphigus bursarius)
Photo: Magnus Gammelgaard
If you locate such galls please send for your children!
With a sharp knife or another sharp instrument, it is not difficult to open the galls to see what is inside. The galls contain small grey waxy aphids. And as you can see, the are kept well protected from outside coming influence, because of the swollen plant tissue.
If you open those galls on the petiole of poplar leafs, the grey waxy aphids will be visible.(Pemphigus bursarius).
Photo: Magnus Gammelgaard
Lettuce root aphids have as many other aphids the habit of changing host. This means that the longest part of the life cycle goes on at the main host. In this case poplar are the main host or the primary host and lettuce, chicory are the secondary hosts.
In the genus of poplar the species Pupulus italica and Populus nigra supposed to bee the main hosts.
In lettuce it is the roots, which are attacked.
The Aphids are over wintering as eggs connected to bud scales on poplar. At the time for foliation the eggs are hatching and the young individuals are making the petioles to swell and forming galls, by their sucking.
Inside the galls the females are giving birth to young aphids with wings and when the galls are opening they can fly to the secondary host, young lettuce plants.
The arriving aphids first feed on the leaves, but after a short time a new type of aphids are born and they are capable to feed on the roots.
The species Pemphigus bursarius (lettuce root aphid) are often difficult to be distinguished with the Pemphigus spirothega. However this one are also forming galls on poplar, but those galls are much more spiral formed.
At the adress: http://www.inra.fr/Internet/Produits/HYPPZ/IMAGES/7032601.jpg
You can see attack on roots of lettuce and a white fluffy network.
On the roots off lettuce the nonsexual stages goes on. Late in the summer or beginning of autumn, winged male and females are born and they will return to poplar to mate and end the life cycle. ses angreb på rødderne af salat som et hvidt uldent netværk.
However it has been shown that a part of the population is able to over winter in the soil and therefore able to directly attack young roots in the spring/summer. This goes on without any mating. Damage
Attack on poplar has no important for the growth of the trees. Under certain conditions when the lettuce plant are weekend because of non favourable growing conditions, a heavy attack can inhibit the growth, but normally you will not see any serious damage of great important.
At the commercial growers, the lettuce often is treated with insecticides before planting and those insecticides have a side effect on lettuce root aphids:
se evt: Middeldatabasen
Growing precautions. The plants should be kept in optimal growth without lack of water and fertilizer. Growing lettuce a distance from poplar should also influence in minor level of aphids attack
Attack from lettuce root aphids has no serious important, and should therefore not be treated neither on lettuce nor on poplar.
Growing precautions. The plants should be kept in optimal growth without lack of water and fertilizer.
Growing lettuce a distance from poplar should also influence in minor level of aphids attack.
If You want to read more about aphids in general, please go to: bladluseng.htm
Other root Aphids:
Opdateret d. 21.1.2012