March Pest of the Month: Phytopythium

Phytopythium is a relatively newly recognised genus closely related to Pythium and Phytophthora. These groups are not true fungi and commonly known as water moulds. Phytopythium is commonly found in production nurseries causing symptoms similar to Pythium, e.g. pre and post emergence damping off, lack of vigour, nutrient deficiency symptoms and root rot. Some species can cause dieback of woody nursery stock.

Similar to other water moulds, Phytopythium have a motile stage, where spores can swim through water to infect the roots of nearby plants. Management must be focused on preventing infection through good nursery hygiene and best management practices, for example:

  • Appropriate drainage across the nursery, avoiding water pooling between containers
  • Good irrigation practices ensuring that plants are not overwatered
  • Disinfestation of irrigation water or otherwise using water that is clean, such as town water
  • Best practice management of growing media including fertiliser management, PH, air-filled porosity etc.
  • Disinfesting benches, growing areas and equipment between crops
  • Taking cuttings from healthy, vigorous mother stock and propagative material
  • Store your growing media optimally, preferably on concrete, covered and in such a way that water and organic matter do not contaminate the media prior to use.

For more information on Phytopythium refer to the new factsheet on the APPS website. If you suspect your stock is suffering from Phytopythium or similar organism it is recommended to submit plants for diagnostic testing at one of the many services around Australia. In addition, all production nurseries receive 6 free samples with Grow Help through a nursery levy, Hort innovation and Queensland Government funded project.

Figure Caption: Dieback in rosemary caused by Phytopythium.