The wax is produced after each moult so newly moulted individuals lack the wax coating, the main purpose of which is thought to be to prevent the honeydew secreted by the aphids to contaminate them but it may also produce a shelter from the weather and from parasites and predators. In many populations reproduction is wholly asexual and nymphs are produced by parthenogenesis. The nymphs are salmon pink in colour with dark eyes and circular cornicles which are slightly raised from the surface of the abdomen. The nymphs go through four instar moults before becoming an imago. The earliest stages are known as crawlers and they do not produce the waxy filaments until they settle to feed.
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In addition, 73 species of predatory insects belonging to five orders and seven families Coccinellidae, Chrysopidae, Hemerobiidae, Forficulidae, Lygaeidae, Syrphidae and Cecidomyiidae have been reported to feed on E.
Verticillium lecanii is the only fungal pathogen known to infect E. This parasitoid, which originates from the USA, is now widespread and has been introduced into many apple-growing regions as a biological control agent. The hyperparasitoids Asaphes vulgaris, A. Predation of E. Exclusion and feeding experiments performed in Poland showed that Exochomus quadripustulatus played an important role in controlling E. Impact Top of page E.
It infests both the canopy and root system of apple trees, although root damage is usually more severe than stem damage. Root damage is also harder to detect and more difficult to control. Thakur and Dogra cited E. In a year of high fruit production, there was a significant reduction in the number of fruit and weight of fruit per tree, partly because of increased fruit drop and reduced fruit set.
Average yield losses were 2. Aphids were observed on only Brown et al. Disruption of root xylem, resulting in resistance to water conduction, is one mechanism by which E.
Heavy infestations may result in the formation of swellings and wounds that permit the entry of the fungi Nectria ditissima and N. Heavily infested trees lack vigour, due to disturbances in nutrient balance, but it is usually difficult to separate the various direct and indirect effects of aphid feeding.
Fruit can be directly affected, through the deposition of honeydew from colonies feeding on adjacent branches or twigs. These can cause cosmetic damage and lead to the growth of sooty moulds on the apples. Weber and Brown reported that aphids can sometimes infest the cores of some cultivars.
Damage is particularly severe in young trees. Roots of nursery trees, for example, can be particularly affected. Mature trees are often little affected, even though levels of infestation are generally greatest in orchards over 25 years old Molinari, Detection and Inspection Top of page E. Inspect for aphid presence on aerial plant parts by looking for whitish colonies on branches, especially around healing pruning cuts or wounds in the bark, throughout mid- to late-summer.
In Massachusetts, USA, standard inspection involves examining five prunings per tree, on one tree per 3. Aphids generally show a preference for the lower part of the canopy and the trunk. At low infestations, E. However, E. Previous records of E. Records describing E. Prevention and Control Top of page Due to the variable regulations around de registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control.
Biological Control The chalcidoid parasite Aphelinus mali has been introduced into many countries in attempts to control E.
It was originally native to the USA, but has become acclimatized in Europe and has now been introduced into apple-growing regions worldwide. Where aboveground infestations dominate, control of E. A review of the history and results of biological control of this pest is provided by Clausen In laboratory studies performed by Mueller et al.
In field studies undertaken in New Zealand, Shaw et al. High levels of parasitism by A. In the Netherlands, the predatory coccinellid Exochomus quadripustulatus is the most common and most widespread coccinellid in apple orchards, and contributes to aphid control alongside A.
In India, releases of A.
Puceron lanigère du pommier
EPPO Global Database