Bacterial leaf scorch of blueberry: a new disease caused by Xylella fastidiosa
During the last 5 years, a new disease initially described as ‘yellow twig’ and then as ‘bacterial leaf scorch’ has been observed on blueberries (Vaccinium spp.) in the south of Georgia, USA. Initial symptoms are leaf marginal chlorosis which then enlarges to the whole leaf. Early leaf fall occurs, and thin, yellow twigs become apparent on some cultivars. Studies carried out in 2006-2007 (ELISA, inoculation tests to verify Koch’s postulates) confirmed that the causal agent of ‘bacterial leaf scorch’ of Vaccinium is Xylella fastidiosa (EPPO A1 List). Initial field surveys conducted in summer 2007 showed that bacterial leaf scorch has the potential to become a major threat to blueberry production in Georgia, especially on highbush blueberry cultivars (hybrids of V. corymbosum, V. ashei, V. darrowi). So far, little is known about the blueberry strain of X. fastidiosa. In the field, the disease only causes problems in southern highbush blueberry cultivars and it is not known whether it could affect other types of Vaccinium (in particular, V. ashei). It is assumed that X. fastidiosa is transmitted through propagation of infected plants but this has not been demonstrated in Vaccinium. The role of insect vectors also needs to be studied further. It is supposed that Homalodisca vitripennis which is abundant in the south of Georgia and known to be a vector of peach phony and grapevine Pierce’s disease, plays an important role in disease spread. Further research will be carried out to better understand the epidemiology of X. fastidiosa in Vaccinium crops and to develop control strategies.
Chang C, Brannen P, Krewer G, Boland R, Donaldson R (2007) Bacterial leaf scorch of blueberry: a new disease caused by Xylella fastidiosa. Phytopathology 97(7 suppl.), S20.
Internet (last retrieved in 2008-03)
University of Georgia (US). Cooperative Extension. Bacterial Leaf Scorch of Blueberry by Phillip M Brannen, Gerard Krewer, Bob Boland, Dan Horton, CJ Chang. http://pubs.caes.uga.edu/caespubs/pubcd/C922/C922.htm