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Chromaphis juglandicola (Kaltenbach)

Insecta, Homoptera, Callaphididae .

Small walnut aphid

Description, Biology, Life Cycle, Damage, Common Names, Images

- Alate parthenogenetic viviparous females, pale yellow in autumn generations often with one or two pairs of black patches dorsally on abdomen; body length about 2 mm.
- Nymphs similar in colour, often with up to four pairs of abdominal black patches.
- Apterous parthenogenetic viviparous females absent. Alate males, similar to the alate females but with head and thorax black.
- Oviparous females apterous, much like nymphs of alate females but with black patches on head, thorax and abdomen.
- Eggs elliptical, shiny black, 1.14x0.57 mm in size.

It lives on the underside of the leaves of walnut, mainly on the terminal leaflet, usually along the veins. The fundatrix hatches from the winter eggs during April and the first days of May, and feeds on the buds or the young foliage.
The first generation and its descendants throughout the spring and summer are all alate parthenogenetic viviparous females until the time for sexual reproduction comes (in all usually 8-11 generations). These alate females are able to spares infestations. The sexual forms occur from September to November. The eggs are laid on the bark of stems, the base of buds or on the leaf scars.
The species overwinters as eggs.
Ants are not attracted by this aphid.

Large populations of the aphid on walnuts can reduce nut quality and yield although the leaves do not appear to react to the insect sucking. The sooty mould fungi supported by the honeydew excreted by the aphids reduce with the vigour of trees.

[R]Common Names
DE: Kleine Walnu▀laus ES: Pulgˇn del Nogal FR: Petit Puceron du noyer IT: Afide minore del noce PT: Piolho da nogueira GB: Small walnut aphid

[R] Images

  1. Chromaphis juglandicola (Kaltenbach) (Coutin R. / OPIE)
    Colony Winged adults and nymphs on the underside of leaf, along the vein.

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