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[R] Juglans regia L. (Juglandaceae).
Fr: Noyer; Ge: Nußbaum; Pt: Nogueira; Sp: Nogal; It: Noce.
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- Very tall tree that may attain heights of 20 to 25 m, widely cultivated in Europe.
- The fruit, which matures in autumn, is a drupe whose green flesh and tough husk (the shell) are inedible (*) . The kernel, called the green walnut, is consumed fresh or dried, and may be used to produce an edible oil. Walnut trees are also cultivated for their wood, very hard and much in demand.
- The principal European producers are Italy and France.
- Walnut trees propagate by seeds planted during the dormant period, grown on for about 6 years, and then grafted. Harvesting occurs in autumn.
- They start to produce at about 6 years of age, are mature at 25 to 40 years and may continue to produce fruit until the age of 70.
- Walnut trees are very sensitive to spring frosts.
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- Diseases: Ink disease (Phytophtora cambivora, P. cinnamomi and P. cactorum) and especially rot due to (Armillaria mellea and Rosellinia necatrix) cause the demise of many older trees in traditional walnut groves where successive plantations have occurred, using as rootstock for the grafts, the common walnut tree, a species particularly sensitive to root diseases.
The bacterial disease (Xanthomonas campestris pv. juglandis) may cause the fruit to drop prematurely resulting in serious crop loss in large, dense plantations.
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- Principal European pests: the codling moth (Cydia pomonella) and the Italian pear scale (Epidiaspis leperii) are the most damaging.
The mussel scale (Lepidosaphes ulmi) and the European brown scale (Eulecanium corni) form crusts on the trunk and branches. The European shot-hole borer (Xyleborus dispar) and the leopard moth (Zeuzera pyrina) attack the wood.
Caloptilia roscipennella Hübner (Lep., Gracillariidae) causes the leaves to curl.
The (Chromaphis juglandicola), the large walnut aphid, Callaphis juglandis (Goeze) (Hom., Callaphididae), the fruit tree red spider mite (Panonychus ulmi) and Eriophyes unguiculatus (Canestrini) (Ac. Phyllocoptidae) attack the leaves.

[R] Images

* Walnut-tree bough (Minost C.)
a: leave dick, with 2-4 pairs of leflets and one terminal leaflet; long petiole; b: catkin hanging, with male flowers; c: fruit: walnut (drupe); d: kernel (shell have been removed).

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HYPPZ on line: Species (scientific names), Pests (common names), Glossary, Crops.

HYP3 : HYPP Phytopathology.

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