Baits will often work if you are looking for a specific Phytophthora. If you want ALL the Phytophthoras, you might do better with PARPH media (https://wiki.bugwood.org/PARPH-V8). This medium will reduce the number of Pythium species you will isolate, and discourages most true fungi. It isn't perfect, though. Nothing is perfect.

Hi Nina, greetings from Vancouver Island, British Columbia, Canada. Hope all is well.. My favorite baiting techniques for isolating Phytophthora spp. from soil are: 1) using Pear fruit and place the pear in a mixture of soil and distilled water in a Ziploc bag . You will notice in few days formation of lesions on the pear. Take samples of the periphery of the lesion and plate them on PARPH-CMA (Selective media for Phytophthora); 2( I used germinated lupin seeds- make a hole on a Styrofoam let the germinated lupin germinate through the hole on top of a plastic container which contains your soil mixed with distilled water. If you wish you can use rhododendron leaves floated in a container which contains your soil with distilled water. Good luck for fishing for Phytophthora spp :-)

One easy way to recover Phytophthora species is to make soil leachate, serially dilute it and plate it in Phytophthora specific media. Serial dilution could help in getting single colonies.

Hello, For me I would use Irish potato. Cut the potato's flesh and let it rest on the soil sample for hours like 4. Then incubate the slice on a blotter. Observe your culture after three days. subculture your colonies on selective media like PARPH-CMA, v8 juice, or pea media.

Hi Giambattista,

over 30 years we have optimized the methods for isolating Phytophthora spp. from soil, water and different plant tissues and built up a global collection of 15000 strains from more than 200 different Phytophthora species. For soil isolations, the by far best method is the Fagaceae leaf baiting method. We have recently published a book chapter on "Survey and Monitoring of Phytophthora Species in Natural Ecosystems: Methods for Sampling, Isolation, Purification, Storage, and Pathogenicity Tests" which shows a wide range of Phytophthora field and lab methods in detail with lots of small tricks that we can never publish in peer-reviewed articles due to ignorant reviewers.

Send me an email to [email protected] and we can discuss this further.

Cheers

Thomas

Baiting with immature carnation petals works very well for me. But they must be very immature, inside the bud, before they turn their colour. Although I would certainly follow Thomas Jung's recommendations, he is an eminence.

Hi Giambattista,

We normally use rose petals (make sure there are no pesticides left on them) to bait the zoospores released from the soil. This works very well for us.

The medium (V8) should be added with pimaricin (10 mg/L), rifampicin (10 mg/L) and hymexazol (50 mg/L; important component - it may suppress the growth of Pythium more than/rather than Phytophthora). You can refer to the method in our paper at: Article Pathogenicity and fungicide sensitivity of Phytophthora parv...

In addition, when colonies are found on the medium, microscopy should be used to detect which colonies are Phytophthora before transferring them to new media.

You should also refer to Thomas Jung's recommendations as he has extensive experience in isolating and identifying Phytophthora spp..

Good luck,