I have been growing roses - between 250 and 300 - for nearly thirty years down on the Flats in Vancouver, and have only rarely had a problem with rust. This year, however, several roses seem to be badly infected. Could this be the result of such a long, wet Winter/Spring, and, if the garden continues to be afflicted in this way, is the only answer to raize the entire garden and start over? The spores must be absolutely everywhere and I despair of ever having the garden free of the disease.
my Fair Bianca here also has rust. I have never seen rust on a FB. You DO NOT need to raize the entire garden. Really bad bushes, can at this point be cut back to the ground. Others can be sprayed throughly with fungicide, after you have plucked the really severely infected leaves off. IMPORTANT: you must cover the ground now with a HEAVY 3-4 inch layer of organic mulch, such as composted christmas trees, composted leaves, basically any kind of compost you can find that is cheap. Bacteria live in this compost, that EAT fungal spores! When rain falls on the compost, it does NOT splash up, like it does on just soil. Some roses are more susceptible than others, such as Abraham Darby, and those it may be best to just shovel prune. It has been REALLY cold and wet here all spring, and that is why rust has shown up. The Fair Biancas that were cut right back to the ground are really healthy. The FB that was not cut back at all has some rust. Once it has bloomed, in about 2-3 weeks, I am cutting the FB down to the ground and covering it with mulch. I predict that all of my new canes will be healthy. The FB is growing on its own roots, and since it is a descendant of Belle Isis, it has the BI gene for suckering freely from the roots, and it really does. I only have about 100 rose bushes to look after, so 300 must be some fun!!!
Rose leaf fungi mutate rapidly and may sometimes overcome the defenses of cultivars that have previously been resistant. This also serves to explain the regional variation in susceptibility. There is also supposed to be a relationship between nutrient levels within the plants and fungus infestation, deficiencies of specific primary nutrients like phosphorus and potassium being associated with particular types of fungi such as rust and black spot.
I am grateful for your reassuring and very helpful information. Thank you for taking the time to respond to my plea for help. Back to the garden, lots to do!
More on the rust problem: I might add that I had some success slowing it down in the plants nearest my front door by picking off the infected leaves that I could see and hand-spraying the plants like mad and repeatedly with Funginex. At the suggestion of a local professioinal rose grower here, I am also obtaining a commercially-available product called Nova which, according to my farmer niece who has got it for me, comes in quantities sufficient for several generations. This will allow a large sprayer application for the more extensive plantings. The next project is to find a source for some good mulch, perhaps bales of hay until Fall leaves are available. I'll also check up on the make-up of my Vancouver Rose Society fertilizers. Thank you again.
Can you legally use the chemical pesticide "Nova" in Vancouver? The last time I checked the website, it was not listed!
Does "shovel prune" mean to dig it up and dispose of it? If so, I love that expression -- I've never heard it before.
