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The aliurode commonly known as White Greenhouse Fly (scientifically Trialeurodes vaporarium) is a very harmful pest that lurks in plants. We learn to recognize it.
It is winged, small in size, about 1.25 mrn in length. It can be recognized from the similarity to nocturnal butterflies and its white color present on the wings, which differ from the color of the rest of the body, which appears pale yellow.
DAMAGE TO THE VEGETABLE
Numerous apparently immobile parasites occupy the lower part of the leaves, but if disturbed they tend to fly around the entire surface of the leaf which in turn is attacked by a swirling swarm, which slowly expands also in other areas of the plant. The plants that are affected by this type of parasite lose the tonicity of the stem and their foliage undergoes an unstoppable yellowing process, thus allocating the vegetable to drying out. If the plant had fruits, they would be covered by a sticky layer, derived from honey, a sugary substance released by young parasites and by adults that feed on the lower part of the leaf. The honeydew stimulates the proliferation of sooty molds that at a later stage injure the vegetable affecting its vitality. The parasite feeds on the foliage by means of its mouthparts, which presents itself in the shape of a needle, thanks to this peculiarity the insect can continually pin the leaf until complete disfigurement ...
BIRTH AND DEVELOPMENT OF PARASIT
The eggs are circular in shape. Adult females place them on the underside of the leaves. They are conical, they take root perfectly on the surface of the foliage, thanks to some very small vessels, called peduncles. The new-born, the neanids, once they come out of the eggs move rapidly along the surface of the leaf thus remaining immobile. The neanids have a clearly different form from that of the adult species, they are flat and oval in shape. The dominant aspect is their semi-transparency, an element that often makes them not very visible and difficult to recognize. Their growth process takes place thanks to the change in the pigmentation of the insect's body, the translucent effect gradually begins to reach a candid appearance, in fact the nymphs are covered with a white powder, thanks to this passage, they are finally visible and tractable. This growth phase has a specific name "pupa", the species will be adult only when they abandon the pupa shell.
THE DIFFERENT SPECIES OF ALEURODI
The parasite is a polyphagous hemiptera, that is it feeds on any plant, any plant is subject to its attack, often difficult to oppose, since the insect is very resistant to insecticidal treatments, which in some cases if carried out with little experience lead to damage of the plant but not of the parasite. In summer the life cycle of the parasite requires a period of three or four weeks during which the change of several generations is continuous. This dynamism leads to a cycle that is difficult to control.
The insect occurs in different species, such as:
Aleurode of the Phyllirea. Attacks the Phylirea; the pupae appear dark and brown.
Aleurode of the azalea. The insect only damages the evergreen species; this is to be considered a specific form of Trialeurodes vaporarium.
Cabbage Aleurode. The cabbage plant is a species belonging to the Brassicaceae family and therefore subject to the attacks of Aleyrodes brassicae, a parasite that mates throughout the year. After the attack, the plant is surrounded by a thick layer of molasses which causes the crop to become moldy.
Honeysuckle Aleurode. Pupae can be white or yellow, found on honeysuckle or other honeysuckle, such as the Symphoricarpon.
Aleurodedel Vlburnum. Its pupa attacks the Viburnum tinus, it is black, fringed and with white, somewhat waxy mottled.
Rhododendron Aleurode. The insect tends to attack only some species and some Rhododendron hybrids such as Rhododendron campynocarpum, R. catawbiense, R. caucasicum and R. ponticum. The species affected by damage tend to dry out through a yellowing process of the foliage.
In greenhouse crops the problem is frequent as the development of the parasite is always in progress. An effective method is the use of spray insecticides or administered by aerosol. The useful active principle to be used is that of pirimphosmetyl, a substance that acts both on adults and on species under development. It is necessary to check the degree of toxicity and the compatibility that the product has with the plant to be treated, in such a way as to prevent the latter from drying out or having damage. For the fruit and vegetable species, therefore edible crops, it is necessary to carry out some treatment intervals, equal to three or four days. In addition to chemical methods, there is an effective natural method which consists in the use of the Encarsia formosa parasitic wasp, capable of destroying the nymphs. This wasp is a very thin hymenopter, able to lay down in 15 days a quantity of eggs such as to manage to eradicate 50 Aleurode neanids. Each egg laid on the nymph, when hatched, causes the larva to become brown, therefore recognizable and attacked by the wasp. To remember that this hymenoptera lives in the presence of temperatures not lower than 13 ° C.