Orchid rust: Puccinia pneumoniae

(Uredo behnickiana), synonym: American summer rust (Uredo amertcana).

The sexual sporophore (O) and rust sporophore (I) of the pathogen are unknown. Summer spore pile (11) is mostly born on the back of leaves and has orange summer spores, but winter spore pile (dish) is not seen.

(1) harm: this pathogen was found on Oncidium in Germany in 1905, and this rust was found on Crane in Cuba in 1954. The disease weakens the growth of the plant and kills the plant in severe cases. The species of damage are Cattlrya citrina, C.dowiana, C.dowianaaurea, C. guttata, Epidendrumvitellinum.marttae, E.alatum.Laelza ancops,L.antumnalls,Onctdtumcavendtshlanum,O.crispum,O.marshalltanum,O.vartcosum,Schomburgkiaundulata, Phaius granddellus, etc.

(2) symptoms: on Crane pinnatifida, the disease appeared as an orange blister pile on the back of the leaf, which was small at the initial stage, then rapidly expanded into a circular ring, and finally the back of the leaf was completely covered by blister. There is a yellowish-green chlorosis zone on the front of the leaf corresponding to the plaque. The seriously infected plants can still blossom, but compared with the normal plants, the flowers are few and small, and the leaf area of each round of new leaves gradually shrinks, and finally fades completely and grows and shrinks, which should usually be removed.

(3) Control methods: once the disease is formed, it can not be controlled, the pathogen spreads widely in the leaves, and its hyphae can extend far in the leaves, far beyond the scope of the spore pile produced under the epidermis. Bacteria can not enter the growing point, only in the leaves, there is no feasible chemical treatment, so the disease can only destroy all infected plants, susceptible varieties should be checked weekly.

Liu Zhongjian