Disease Cycle
The disease cycle of rose powdery mildew starts when the sexual spores, ascospores, of the pathogen survive the winter in a structure composed of hyphae called an ascocarp. The specific ascocarp is a chasmothecium, or cleistothecium, and has a circular shape to it. Under the right conditions the chasmothecium will break open to reveal the asci, which is another long tube-like structure which contain the ascospores. These ascospores are then released and spread by wind, insects, and rain until they land on a susceptible rose for a host and land, attach, and germinate on the plant. They will also produce condia, the asexual spores of Podosphaera pannosa, which will spread throughout the summer. It is these long chains of white conidia which give the fungi its characteristic “powdery” appearance. Late in the year as the plant is dying cleistothecia will again form when the ascogonium receives the nucleus from the antheridium.
Read more about this topic: Podosphaera Pannosa
Famous quotes containing the words disease and/or cycle:
“Anti-Semitism is a horrible disease from which nobody is immune, and it has a kind of evil fascination that makes an enlightened person draw near the source of infection, supposedly in a scientific spirit, but really to sniff the vapors and dally with the possibility.”
—Mary McCarthy (1912–1989)
“The cycle of the machine is now coming to an end. Man has learned much in the hard discipline and the shrewd, unflinching grasp of practical possibilities that the machine has provided in the last three centuries: but we can no more continue to live in the world of the machine than we could live successfully on the barren surface of the moon.”
—Lewis Mumford (1895–1990)