Mint rust on cultivated peppermint in Canterbury: Disease cycle and control by flaming

Abstract The disease cycle of mint rust (Puccinia menthae Pers.) was studied for 2 years in peppermint (Mentha × piperita L.) crops in Canterbury. Pycnia and aecia were present from August to late October, and the uredinial stage appeared in early October. Teliospores were produced in association with the uredinial stage in spring (September–December), but production of overwintering teliospores commenced in late February, as urediniospore production decreased. The uredinial stage persisted through one of the two winters, but its importance as a means of overwintering was not assessed. Autumn cultivation reduced the incidence of rust infection in the following spring. From observations on the timing of the disease cycle, the optimum time to flame for rust control in Canterbury would appear to be September, when the aecial stage is present, but before the uredinial stage appears. The latent period of the uredinial stage decreased with increasing mean air temperature, reaching a minimum of 12 days at c. 20°...