Influence of sowing dates on Pseudomonas syringae pv. pisi
Pseudomonas syringae pv. pisi (EPPO A2 quarantine pest) was first found in United Kingdom in 1985, and statutory action was taken in 1987 to eliminate this pathogen by seed testing and notification of infection in field peas. However, these statutory controls were removed in 1993 due to the standardization of phytosanitary regulations within the European Union. During 1995, P. syringae pv. pisi was reported in several crops of winter peas in United Kingdom, and in particular it occurred in a field trial which was used to evaluate the influence of sowing dates on the epidemiology of the disease. The disease development in the winter cultivars Rafale, Frilene and Froidure was compared with that in the spring cultivars Baccara, Conquest and Bohatyr, each sown on six dates (October, November, December, mid-March, late-March, April). The results showed that the disease incidence had reached 100;% plants in all treatments by mid-July, and that the disease was more severe on peas sown in autumn and winter than in spring. It was also found that spring cultivars are affected more severely than winter cultivars. The initial source of the infection is not certain, but is thought to be related with infected seeds. Other studies on seed samples have demonstrated that since the removal of statutory controls, the incidence of seed infection has increased (it reached 36.5% of tested samples in 1994). The authors noted that in the absence of statutory controls, the level of seed infection is likely to have increased to date, particularly on winter peas.
Sources
Mansfield, P.J.; Wilson, D.W.; Heath, M.C.; Saunders, P.J. (1997) Development of pea bacterial blight caused by Pseudomonas syringae pv. pisi in winter and spring cultivars of combining peas (Pisum sativum) with different sowing dates.
Annals of applied Biology, 131(2), 245-258.