Phytophthora Landscape Bed Update: August 2018

As of August 16, 2018, almost all of the suspected tolerant or resistant plants were healthy and are considered to be in good-to-excellent condition. P. nicotianae was isolated from plants known to be susceptible to Phytophthora species and this confirms that the inoculum is active.

Interestingly, 1 zinnia and 1 petunia cultivar that were suspected to be resistant or tolerant have died and P. nicotianae was determined to be the causal agent. Another plant pathogen,Verticillium dahliae, was isolated from Rudbeckia hirta ‘Indian Summer’.

P. drechsleri and P. tropicalis have not been isolated from any of the susceptible controls or tolerant or resistant cultivars. Two cultivars of phlox and two cultivars of African marigold are in fair-to-poor condition from an unknown cause, but no species of Phytophthora have been isolated from these plants.

The landscape beds will be evaluated until October 2018. At that time, 1 plant of each species from each bed will be removed and assayed for the presence of Phytophthora on the roots or stem.

Enjoy some photos below and stay tuned for final results!