Can the Seed Trade Provide a Potential Pathway for the Global Distribution of Foliar Pathogens? An Investigation into the Use of Heat Treatments to Reduce Risk of Transmission via Seed Stock.

The international plant trade results in the accidental movement of invasive pests and pathogens, and has contributed significantly to recent range expansion of pathogens including Seeds are usually thought to present a lower biosecurity risk than plants, but the importation of seeds from North America to Britain in the mid-1900s, and similarities between British and Canadian populations suggests seeds could be a pathway. has not been isolated from seeds, but inadequately cleaned seed material could contain infected needle fragments. This case study investigated whether cone kilning, and wet and dry heat treatments could reduce transmission without damaging seed viability. needles infected with were incubated alongside cones undergoing three commercial seed extraction processes. Additional needles were exposed to temperatures ranging from 10 to 67 °C dry heat for up to 48 h, or incubated in water heated to between 20 and 60 °C for up to one hour. seeds were exposed to 60 and 65 dry heat °C for 48 h, and further seed samples incubated in water heated to between 20 and 60 °C for up to one hour. survived the three kilning processes and while seeds were not damaged by dry heat exceeding 63.5 °C, at this temperature no survived. Wet heat treatments resulted in less than 10% pathogen survival following incubation at 40 °C, while at this temperature the seeds suffered no significant impacts, even when submerged for one hour. Thus, commercial seed kilning could allow transmission, but elevated wet and dry heat treatments could be applied to seed stock to minimise pathogen risk without significantly damaging seed viability.