Some studies on bacterial brown spot of orchids caused by Pseudomonas cattleyae (Pavarino) Saverlesco

The disease developed in leaves of Phalaenopsis equestris and V. lamellata infiltrated with bacterial suspension of 1.4 x 10 to the sixth power to 1.4 x 10 to the ninth power cells per ml. No disease developed at inoculum levels lower than 1.4 x 10 to the first power cells per m. Host range studies showed that the bacterium was also pathogenic to 13 other orchids namely: Aranda 'Deborah', Cymbidium finlaysonianum, Renanthera philipinensis, R. storiei, Trichoglottis brachiata, T. ionosma, T. wenzelli, Vanda lamellata, V. Miss Joaquin, Vanda T.M.A., Vandopsis lissochiloides and Dendrobium hybrids D x 43 and D x 37. The hypersensitive reactions of Phalaenopsis equestris to other phytopathogenic pseudomonas ranged from weak or partial to total necrosis of the leaf areas infiltered with bacterial suspension. Inoculum studies showed that the bacterium infected host tissues only in the presence of wounds