Rust on roses is a fungal disease that causes the tops of leaves to turn yellow, while the undersides are covered with small orange spots.
This is a most serious disease that is most prevalent in the Pacific Northwest.It is caused by the cool, humid climate, and require wet conditions for two to four hours to infect foliage. Although it is most prevalent along gardens in the West Coast, it can occur on roses anywhere in the right conditions.
This fungal disease appears as bright orange spore masses on the undersides of the leaves, starting on the lower branches. The top (or) upper-side of the leaves, the rust mass often has yellowish spots.
If the foliage is severely infected, it may twist or curl, turn brown, and fall off. It can also affect the stems. To help prevent the spread of the disease, keep fallen leaves cleaned up, because the spores will overwinter on them.
Plants affected with this fungus are more prone to winter kill.
Avoid problems of rust fungus on roses by avoiding overhead watering. It is best to water the bushes on the ground, keeping the leaves dry. Also try to avoid wetting foliage any more than necessary. and water early in the day to give any wet leaves time to dry before nightfall.
Before buying roses, shop around...and choose wisely..Select disease resistant varieties. If a certain rose is Not disease resistant, but you positively must have it, be prepared to give it the special attention and care it needs, like regular preventive spraying.
Be sure your roses are planted where they will receive plenty of sun, and good circulation. Keep the bushes thinned out by removing dead canes.
Keeping plants healthy by watering and fertilizing regularly will help prevent many rose diseases.
When using spray, such as garden sulfur, be sure to spray the undersides of the leaves also. Neem oil also reduces rust infection.
I've had reports from readers that they have stopped the spread of the fungus spores by dusting the plants with either cornmeal (from the agriculture store), or by sprinkling a very thin layer of wood ash on the plants.
Both of the above will raise the ph considerably, (this is good because the fungus likes a low ph), It also has a very drying effect, (the spores need a wet environment to grow).
Be warned; if you try the wood ash treatment, wear protective eye ware, as the wind could blow it in your face, and it will burn your eyes!
I've personally experimented with the cornmeal, dusting it on the plants last year, as soon as I saw any sign of trouble on the leaves, and I was amazed with the results!
If you try either of these organic methods, won't you share your results with us? Send comments HERE.