STUDY OF AN OXYCARBOXIN–RESISTANT STRAIN OF PUCCINIA HORIANA.

An oxycarboxin-resistant strain of Puccinia horiana appeared in a french culture of Chrysanthemum, after intensive sprayings with Plantvax to control White Rust.

To inhibit teleutospore and basidiospore germination, the resistant strain requires oxycarboxin concentration 16 times greater than sensitive strains studied.

When oxycarboxin treatments are stopped, the resistance factor (FR) decreases gradually : it proceeds from 16 to 8,5 in 2 months, and to 6 one month later ; the sensitivity comes back after one year without treatment.

Whereas, the resistance is remaining if chrysanthemums are regularly treated.

According to these results, exclusive use of Plantvax must be avoided : others fungicides with different biochemical action have to be included in spray program.

Symposium on Chrysanthemum

F. Montfort, D. Grouet, P. Leroux

https://doi.org/10.17660/ActaHortic.1982.125.26