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| Anthracnose is the rose disease no one talks about. When
people talk about rose diseases, it's Blackspot, Powdery Mildew
and Rust they talk about. It took a couple of years gardening
in the damp to realize that no, I'm not having trouble controlling
blackspot in spring; instead I'm dealing with something else entirely.
Namely anthracnose. Looks very much like blackspot, but prefers
cooler temperatures, in the 50s and 60s where blackspot needs
temperatures above 65 degrees F and we rarely get above 65 in
spring around here but the roses are covered with black spots;
and anthracnose lesions lack the telltale feathery margins and
yellow halos that surround blackspot lesions. The margins are
entire and no halos. Spots may be purple, black, dark red or brown.
Spots may form on canes too, this is where they overwinter. And
of course my favorite blackspot sprays do nothing for anthracnose.
Gonna have to try something else.
Here's what Iowa State Extension has to say, which is way more
than most rosarians have to say about anthracnose: "Anthracnose
or spot anthracnose is a disease that appears to be more prevalent
after a wet springs. (the only kind we have here in WA.) Hybrid
teas, as well as old fashioned varieties, are susceptible. World-wide,
this disease seems to be of little importance as there is virtually
no documentation of it in the literature. Symptoms occur as leaf
spots, sometimes running together, they usually are 0.5 centimeters
in diameter, circular with dark red margins. Newly formed spots
are red or purple. Older spots have white centers with a dark-red
margin. A shot-hole effect may occur (the spot itself drops out
of the leaf leaving a circular hole). Defoliation may occur if
the disease is severe." I especially love that 'no documentation'
part. Certainly accurate! just try finding anything on it.
Baldo "Bugman" Villegas has some nice photos on his
site. A very nice site for learning about roses and bugs. He works
for the CA Dept. of Agriculture as an Entomologist and he's active
in the NCNH district of the ARS. Here's his address: sactorose.tripod.com
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