Plum pox show no symptoms on leaves or fruit. Not all infection in "Prunus" are characterized by a ring symptom on leaves. Several cultivars show yellowing line patterns and blotches, or necrotic ring symptoms on expanded leaves. Leaf distortion has also been observed. Infected fruit can develop yellow rings or blotches, or brown rings, and some plum and apricot fruit can be severely deformed and bumpy. The seed of many infected apricots and some plums show rings. Many non-"Prunus" species, in at least nine plant families, have been infected artificially with one or more strains of the plum pox virus, and in
Plum-headed parakeet the French name "Le perruche a teste bleu" and the Latin name "Psittaca cyanocephalos". Although Brisson coined Latin names, these do not conform to the binomial system and are not recognised by the International Commission on Zoological Nomenclature. When in 1766 the Swedish naturalist Carl Linnaeus updated his "Systema Naturae" for the twelfth edition he added 240 species that had been previously described by Brisson. One of these was the plum-headed parakeet. Linnaeus included a terse description, coined the binomial name "Psittacus cyanocephalus" and cited Brisson's work. The specific name "cyanocephalus/cyanocephala" combines the Ancient Greek words "kuanos" "dark-blue" and "-kephalos"