Twenty-two biotypes of Conyza canadensis (Canadian fleabane, horseweed) from a conventional orchard in Crete displayed varying degrees of reduced glyphosate susceptibility in standard whole plant assays. A refined shikimate leaf disc assay was developed to precisely determine the resistance levels, permitting early detection of resistance evolution and integrated management of the weed. The 5-enolpyruvoylshikimate-3-phosphate synthase (EPSPS) homologue genes (1 and 2) were sequenced for three different biotypes (one of reduced susceptibility from Crete, one resistant from mainland Greece and one resistant from the USA), and no amino acid substitution of Pro106 was found. Real-time qRT-PCR was used to study the expression profiles for EPSPS and the M10 and M11 ABC transporter genes, following glyphosate application. The expression levels of the EPSPS genes were not significantly altered following glyphosate application in any biotype, but both M10 and M11 were found to be highly upregulated in glyphosate-treated reduced susceptibility or resistant biotypes and not in a susceptible biotype. These results are in accordance with data recently reported by other researchers, supporting a role of the M10 and M11 ABC transporter genes in glyphosate resistance in Conyza canadensis, because of reduced translocation.

Sporadic incidences of Citrus tristeza virus (CTV) in western Crete resulting from the introduction of a mild strain (Spanish isolate T385) have been reported previously. Further analysis within this region has identified an emerging second CTV strain with minimal genetic divergence, sharing 99% nucleotide identity with the severe stem‐pitting isolate Taiwan‐Pum/SP/T1. Other severe isolates from the Mediterranean region appear in the same phylogenetic cluster, indicating movement or new introductions and the need for targeted control actions and improved phytosanitary measures in this area.