The ashy plant louse of the apple tree ( Dysaphis plantaginea ) is a large Puceron Aptère of 2,5 Misters It is harmful only with the Pommier; the secondary plant-host is the Plantain, in particular Plantago lanceolata.

Description

The winged adult is green dark with a brilliant spot in the middle of the Abdomen. He globulous, green-olive-is purplished with mauve, is covered with a pubescence blanchâtre. He has long Cornicule S maroon dark; Cauda very short, strongly conical.

Its eggs are lengthened and black.

Biology

The egg of winter is deposited in autumn at the base of the Bourgeon S or under the barks of the wood from two to four years. It hatches during the swelling of the buds, giving a founder, who generates by Parthénogénèse, approximately 70 Virgine S apterous. Important colonies develop with the lower face of the sheets or on the branches. The apterous virgines generate Sexupare S apterous, winged, and males (Polymorphisme). The wings measure practically the double length of the body. The winged ones, the proportion increases gradually, migrate on the plantain. The dispersion of the apterous forms on other trees is ensured by the wind.

Life cycle

One counts 6 to 9 generations per annum.

The colonies are formed in April, at the time of the flowering of the apple tree. The winged ones appear at the end of May and migrate on the plantain until the end of July.

To the autumn, like all the plant louses dioecic S, the winged adults turn over on the sheets of the apple trees and are at the origin of the eggs of winter which correspond to the wintering form. For this reason, the varieties of apple tree with long cycle (those which keep their sheets with the autumn tardily) like Granny Smith or Pink Lady ‚is more sensitive to the ashy plant louses.

Damage

The ashy plant louse is most dangerous of the plant louses of the apple tree because of its high potential of multiplication and its great noxiousness. Relatively weak populations cause already a strong rolling up of the sheets. This plant louse causes, by its punctures, of serious deformations of the vegetable bodies. The Feuille S are recroquevillent and been able to fall, the branches are deformed, the physiological fall is opposed, the fruits remain many, small and embossed. In addition, this plant louse rejects abundant a Miellat on which the Fumagine develops.

Treatments

It is recommended to concentrate on the low parts of the crowns close to the trunk, from where the infestations extend thereafter.

The traditional fight against the plant louses dioecic consists of the realization of treatments containing mineral oil at exit of winter on larval eggs and the first stages, to limit the pressure. And when that is necessary and that approved active matters exist, of the treatments Insecticide S are realized in complement later in season.

In Organic farming, one uses with the autumn stripping or of the Argile Kaolinite calcined (trade name: Surround WP and ARGIREC B24) in pulverization to form a protective coating on the sheets of apple trees during the migration of the individuals sexués of the plant louse of his secondary host (the plantain in the case of the ashy plant louse) towards the primary education host (the apple tree). Thus, the plant louses do not seem any more to regard the apple trees covered with this clay film as their primary education host.

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