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 curculio egg cavity, leaving the egg in a flap of flesh and causing a crescent-shaped scar on the outside of the fruit. Without this curved slit, eggs are killed by pressure from the growth of the host fruit. Plum curculio larvae are typically 6 to 9 mm long when fully grown, when they reach the pupal stage measuring about 5 to 7 mm; all adult characteristics are visible in this stage prior to transformation. Adult plum curculio are about 4 to 6 mm long and have a small, rough snout colored with black, gray, and brown specks. Four pairs of ridges