Detection of Xylella fastidiosa in peach
The distribution of Xylellla fastidiosa (EPPO A1 organism) causal agent of the phony peach disease within roots of peach was studied in Florida, US.
The bacterium could be detected in all trees, whether symptomatic or asymptomatic for phony peach disease. The distribution of X. fastidiosa in the roots of symptomatic trees was uniform along the length of the roots and within the root ball. The distribution of the bacterium was not influenced by the distance the root sample was taken from the trunk or the diameter of the root piece sampled.
The authors found that the minimum sample to detect, at a risk of 5%, the disease in asymptomatic trees should consist of 5 - 10 roots.
Sources
Aldrich, J.H.; Gould, A.B.; Martin, F.G. (1992) Distribution of Xylella fastidiosa within roots of peach.
Plant Disease 76, 885-888.