Situation of peach mosaic in North America
As reported previously in EPPO RS 96/175, the American peach mosaic disease is not caused by peach latent mosaic viroid (EPPO A1 quarantine pest – quarantine status under review). Peach mosaic might be associated with an uncharacterized flexuous virus (James ; Howell, 1997). Peach mosaic disease was initially discovered in 1931 in the Western USA (Texas and Colorado), and later in the states of California, Utah, New Mexico, Arizona and also in nearby Mexico. It only affects Prunus species: P. persica (peach), P. persica var. nectarina (nectarine), P. dulcis (almond), P. armeniaca (apricot), P. besseyi, P. serrulata and several species of plum. The main affected hosts are peaches and nectarines. Peach mosaic retards bud development in spring, deforms flower petals and causes flower breaking, foliar mosaic, leaf deformation, shoot rosetting. Diseased fruits are deformed (bumpy) and cannot be marketed. A rapid spread of the disease was observed during 1932-1935, especially in California and Colorado. Quarantine programmes were started in 1936. Spread of peach mosaic to peach production regions situated in the east of the Mississippi river could be prevented, but total tree losses in California and Colorado before 1995 exceeded 390,000 trees. Then, a decrease in incidence was observed. For example in Colorado, annual tree losses dropped below 1,000 in 1960, below 100 in 1969, below 10 in 1982, below one in 1983, and finally to zero in 1987. In Colorado, the only documented incidence since 1987 occurred in 1991. It is felt that the current rarity of the disease reflects the success of the control programme. The situation in Mexico where no such programme was applied, is quite different and symptomatic trees were commonly observed as recently as in 1993 (Larsen, 1997; Larsen et al., 1997).
Sources
James, D.; Howell, W.E. (1997) Identification of a flexuous virus associated with peach mosaic disease.
Abstract of a paper presented at the ISHS XVII International Symposium on virus diseases of fruit trees, Bethesda, US, 1997-06-23/27, p 75.
Larsen, H.J. (1997) Impact and control of peach mosaic in North America.
Abstract of a paper presented at the ISHS XVII International Symposium on virus diseases of fruit trees, Bethesda, US, 1997-06-23/27, p 72.
Larsen, H.J; Hatch, A.H.; Yu, K.S. (1997) Expression of peach mosaic symptoms in nectarine and peach cultivars.
Abstract of a paper presented at the ISHS XVII International Symposium on virus diseases of fruit trees, Bethesda, US, 1997-06-23/27, p 74.