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Aphids on walnut (Juglans)Species Overview: Chromaphis juglandicolae Myzus persicae Panaphis juglandis Species of walnut
Aphids on walnut
Blackman & Eastop list about 20 species of aphids as feeding on walnut species worldwide, and provides formal identification keys for aphids on Juglans. About 20 species of aphids feed on the various species of walnut worldwide. The main aphid genera are Stomaphis, Panaphis, Chromaphis and Monelliopsis; the latter is exclusively North American.
Of the 8 aphid species Blackman & Eastop list as feeding on European Walnut (Juglans regia) Baker (2015) lists 3 as occurring in Britain: Chromaphis juglandicola, Myzus persicae and Panaphis juglandis.
Bell et al. (2015) (Appendix S2) have also published an "annotated checklist of aphids present in the UK". We discuss some of the reasons for the differences between Baker's and Bell's lists in our rare aphids page.
The species below are those we have found most frequently, listed in rough order of abundance. Note that walnut is prone to having accidentals attempting to feed on it, such as the common sycamore aphid (Drepanosiphum platanoidis ). Assistance on identifying European walnut is given below.
The small walnut aphid lives scattered on the undersides of leaves of walnut (Juglans regia). Oviparae and males occur in May-June in India, and in autumn in Europe and the USA. It is found in Europe, Central Asia, India, Pakistan, China and North America.
They live on the upper sides of leaves of walnut (Juglans regia), in rows along the veins, and are often ant-attended. Sexual forms occur in September-October. The species is rarely found together with the small walnut aphid, supposedly because it is adversely affected by the rain of honeydew from the other species. It occurs in Europe, and parts of central Asia, Pakistan and was introduced into the western USA.
The peach-potato aphid does host alternate where the primary host - peach (Prunus persica) occurs. Eggs are laid on the primary host and spring colonies curl the young leaves. However, most of the population overwinters as mobile stages on herbaceous plants and brassicas. Myzus persicae is a major pest on its summer hosts including potatoes, sugar beet, lettuce, brassicas and legumes, mainly because it transmits a number of important plant viruses. Myzus persicae is a polyphagous generalist.
We cover only one species of walnut, the European walnut (Juglans regia), shown flowering below. The leaves are alternately arranged, 25-40 cm long each with 5-9 leaflets.