A P R I L 2 0 1 8 POTATO GROWER 23 Only In Australia. sion of trade in all potatoes from Western Australia due to the discov- ery of the Tomato Potato Psyllid. That is the psyllid that can transmit Candidatus Liberibacter solanacearum (Lso), the organism that causes zebra chip symptoms. Lso has not been found in Western Australia and dis- cussions are ongoing on risk mitiga- tion. Plant quarantine has not kept the golden nematode out of parts of the country, but an in-country quaran- tine has limited the damage that such a pest can cause to exports. Seed potato certification is actively involved in implementing meas- ures, such as soil sampling of all fields used to produce seed, and, as such assists in enabling export trade to continue. An example of how successful these efforts to promote export trade have been was the sign- ing by Australia and Indonesia of a bilateral agreement allowing seed potato exports from South Australia and Victoria into Indonesia, while I was in the area. Factors such as modern farming techniques and the use of certified seed potatoes are mentioned as rea- sons why potato yields in Australia improved so much since the fifties. Average yields went up five-fold, however the acreage decreased. Seed potato certification agencies were originally set up state wide, but the Victoria Certified Seed Potato Authority (ViCSPA) now covers more than just the state of Victoria. The ViCSPA has expanded over the years to South Australia and some areas in New South Wales. This makes ViCSPA the largest seed certi- fication authority in Australia, certi- fying some 4,750 acres annually. With the arrival of PVY the produc- tion of seed potatoes became more difficult in the traditional areas. Existing aphid pressure is the main reason why isolation is the only way to keep seed potatoes virus free. We can find an example of this in the US in North Dakota and Minnesota, where the potato industry obtains clean low generation seed potatoes from farms that are isolated from the commercial areas. Similar to that principle, changes have taken place