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Lettuce Root Aphids



P_lettrtaphid

Lettuce Root Aphids

Usually appear in

Summer


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Caused By:-     The Root Aphid Pemphigus bursarius L.

Description

Te Lettuce Root Aphid(Pemphigus bursarius) on Cichorium intybus. Picture from Wikimedia Commons.
There are several types of Root Aphids specific to certain plants. Lucikily they are usually rare except in certain circumstances.
The Lettuce Root Aphids(Pemphigus bursarius L.) have a complex life cycle which switch between Lombardy poplar(Populus nigra) in the winter and Lettuce in the summer.
They may well attack related plants or weeds other than Lettuce. As the name suggests these aphids attack the roots of Lettuce. Plants heavily attacked by this aphid may wilt during the day. The developing heads remain soft, fail to develop properly, and yields are reduced. Extremely heavy aphid populations over a prolonged period can cause collapse and death of the plant.
Individual rootlets turn brown and die. They usually look like masses of white, woolly material or powder on the roots of the affected plants.
Lettuce root aphids can be distinguished from other aphids found on lettuce by their short antennae (less than one-third body length) and undeveloped cornicles( wax producing appendages) on the rear of their bodies. The aphids on the roots of lettuce are the nonsexual stages of the aphids. Late in the summer or beginning of autumn, winged male and females are born and they will then mate and lay eggs under the bark or bud scales of poplars.
In heavy infestation some of the non-sexual aphids can survive the winter in the soil to re-infect other lettuce. The over-wintering eggs at the time of leaf formation hatches and the young feeding activities make the leaf petiole swell and form galls. Inside the galls the females give birth to young aphids with wings and when the galls open they can fly to the secondary host of young lettuce plants. If you open those galls on the petiole of Lombardy poplar leafs, the grey waxy aphids will be visible.
The arriving aphids first feed on the leaves of the Lettuce, but after a short time a new type of aphids are produced which are capable of feeding on the roots.
Attack on poplar has no important for the growth of the poplar trees.
See also these other aphids Aphids, Blackfly, Cypress, Green Spruce, Honeysuckle, Juniper, Lupins, Mealy Cabbage, Mealy Plum, Melon Cotton, Peach, Rose, Willow Bark Aphid, Wooly.


Control

Applying insecticide to the soil should help to control the infection if it is caught early enough.
Watering the soil with insecticide or Jayes Fluid or Amarillotox before planting Lettuce should help prevent attack, although some of these chemicals are not licenced for this pesticide use.
If you grow Lettuce and it may be possible remove the Lombardy poplars which are their overwintering host.
If an infestation occurred on the previous crop, work the soil should be worked deeply and allow it to dry thoroughly before replanting to lettuce.
Crop rotation will help prevent a build up of this pest.
Some varieties of lettuce are resistant to this aphid.
There are some predators like Syrphid larvae and Anthocorids which can enter and attack the contents of the gall if applied at the right time.
The larvae of the Chloropids, (Thaumatomyia glabra Mg.) and (T. notata Mg.), are common predators of P. bursarius in the soil.



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