Surveys on phytoplasma diseases of fruit trees in Bulgaria
From 2007 to 2011, official surveys were conducted in selected fruit tree orchards in all 28 districts of Bulgaria. Samples were collected from symptomatic and asymptomatic trees, in late autumn when the phytoplasma concentration in the trees was highest. Priority was given to plant material originating from fruit tree nurseries and mother stock plots. All samples were tested by PCR in the Central Laboratory for Plant Quarantine. As a result, phytoplasma infections were found in 10 out of the 28 investigated districts. ‘Candidatus Phytoplasma mali’ (associated with apple proliferation – EPPO A2 List) and ‘Candidatus Phytoplasma prunorum’ (associated with European stone fruit yellows – EU Annexes) were detected in samples from 5 different districts. Because phytosanitary measures were applied, it was observed that the incidence of apple proliferation in 2009 and 2010 was reduced compared to 2007 and 2008, and no positive cases were detected in 2011. However the situation for European stone fruit yellows was different, as infections were detected in 2, 5 and 5 samples in 2009, 2010, and 2011, respectively. ‘Candidatus Phytoplasma pyri’ (associated with pear decline – EPPO A2 List) was detected in pear samples from 7 different districts*. Infections were detected in 2 samples in 2009, 6 in 2010, and 4 in 2011. All infected pear trees were destroyed (burnt) and affected areas were placed under quarantine. The authors concluded that phytosanitary measures should be taken against ‘Ca. P. prunorum’ and ‘Ca. P. pyri’ to prevent their spread.
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* The EPPO Secretariat previously had no data on the occurrence of ‘Ca. P. pyri’ in Bulgaria.
Sources
Etropolska E, Laginova M (2012) Monitoring distribution of fruit tree phytoplasmas in Bulgaria from 2007 until 2011. Abstract of a paper presented at the 22nd International Conference on virus and other graft transmissible diseases of fruit crops (Roma, 2012-06-3/8), p 22.