Survey methods for citrus tristeza closterovirus
In the Central Valley of California (US), an eradication programme for citrus tristeza closterovirus (EPPO A2 quarantine pest) has been implemented for many years. In such a programme, the sampling scheme and the estimation of the incidence of virus infection are key issues. The sampling scheme was established several years ago as follows: every fifth trees in every fifth row is selected and sampled (in blocks of approximately 400 trees). It is estimated that 4 to 6% of trees are sampled and material from each tree is tested separately. An alternative sampling and testing scheme has been studied and compared by using field data and computer simulation to the current scheme. The alternative scheme is defined as follows: approximately 25 % of trees in a block are sampled, and plant material is collected and tested from groups of 4 trees. Results showed that the alternative method resulted in increased accuracy and precision of estimates of citrus tristeza closterovirus incidence without increasing unduly the number of laboratory test to perform.
Sources
Hugues, G.; Gottwald, T.R. (1998) Survey methods for assessment of citrus tristeza virus incidence.
Phytopathology, 88(7), 715-723.