This project provided continued capacity in plant virology expertise and diagnostics, building industry awareness of viral disease threats, and developing preparedness for viral diseases that pose serious biosecurity threats to the Australian cotton industry. At least six surveys targeting viruses in northern Australia were done in areas that represent possible incursion pathways and also in emerging cotton production regions. No viruses were detected in cotton although six different polerovirus species were detected in other hosts. None of these are thought to be able to infect cotton. Disease surveys in commercial cotton crops in Queensland found no symptoms typical of exotic viruses and generally, there was very low incidence of endemic viruses (cotton bunchy top virus – CBTV and tobacco streak virus - TSV). Three virus surveys in Timor-Leste established that cotton leafroll dwarf virus (CLRDV) was found to be relatively common and widespread in three Gossypium spp. (G. arboreum, G. barbadense and G. hirsutum). Improved diagnostics developed for CLRDV strains from Timor-Leste, Thailand and other countries will support preparedness for this biosecurity threat.