Sources of phytophthora
When purchasing land to grow cutflower species susceptible to Phytophthora, aim to buy land that is free of this pathogen.
Growers should also be aware of potential threats from outside the immediate property, for example infected native vegetation on neighbouring properties or Crown land - particularly those uphill, because run-off and subsoil seepage carrying spores may drain onto the site.
Growers should also ensure that plants for their cutflower operation are disease-free. Buy plants from accredited nurseries if possible. When plants arrive, check any signs of soft discoloured roots, wilting when the growing medium is moist, and abnormal leaf loss.
If possible, and especially if plants are not from an accredited nursery, quarantine plants for four to six weeks under warm conditions, longer during cool weather, in case disease symptoms develop. Have any suspect plants checked by a reputable laboratory.
Should phytophthora be present, it will be difficult to make any claim against a supplier when the plants are already in the ground. Growers also need to be aware that for planting stock imported from interstate or overseas such as bulbs, quarantine regulations only check for and exclude pests and pathogens not already in the state. Therefore, imported stock should also be checked and quarantined prior to planting in the same manner as local stock.
Any water supplies that are in contact with the ground must be suspect, for example dam water or water drawn from streams or soaks. There are well established methods for testing water supplies. If Phytophthora is found then the water should be treated to avoid infecting plants.
Phytophthora may be brought in or moved around in infested water or soil. If a neighbouring property is infected and drainage is towards your property, then over time it is likely that run-off may carry infected water onto your property.
The speed varies. In bushland, for example, rates of spread uphill from about 0.7 to 3.6 metres per year have been recorded. On hillsides the rate of spread downslope can be several hundred metres per year, especially after fires.
Infested soil on vehicles, machinery, tools, footwear or animals can also carry plant pathogens. Adopt the ‘clean on, clean off’ approach.
Minimise the transfer of soil from one area to another by washing down vehicles both on entry to your property, and when leaving. Spades and other tools should always be washed free of soil before and between plantings. Tools should be regularly drenched in a solution of detergent or disinfectant. Footbaths should be used at all entry points or when moving to and from known infected areas.