> We moved to a house with a lovely rose garden, however, that lovely rose
> garden is seriously ill! All the roses (David Austins) are covered in
> black spot. I began to remove the offending leaves before spraying but
> it is too prolific!
> I am completely new to gardening and caring for roses and I as such, I
> have two questions that I hope someone can help me with...
> I was wondering if I could just cut all the rose bushes right back (the
> steams look ill too).
> Can black spot spread to other plants, as my clematis and some weeds,
> are now covered in spots that look very similar!
> Thanks guys.
Blackspot, "Diplocarpon rosae", is a *** fungus that manifests itself
on rose bushes as black spots on leaves progressing to black spots
fringed with yellow rings on both sides of the leaves. As they develop
the spots enlarge. Eventually, as the disease spreads, the entire leaves
will go from green to yellow and then drop to the ground. With time the
entire rose bush may become defoliated. Leaves less than two weeks old
are the most susceptible to this disease.
Once you have discovered that your rose bushes are infected it is best
to prune off the damaged parts of the plant and gather the diseased
foliage. Dispose of this diseased material in bags or burn it. Do not
add to the composter, as the fungus shall only return to haunt you when
you recycle the soil back into the garden. It is vital to do an end of
season cleanup so the spores will have no where to hide over winter.
After having removed the diseased parts from your rose bushes it is
necessary to apply a preventative formula to minimize further attack.
Using fungicidal soap or sulphur several times over the course of summer
is one solution (especially after rain as these products tend to wash
off). There are a few home remedies that have met with some success and
are worth trying, especially for those that really do prefer organic
garden methods. One is a solution made with baking soda: dissolve 1
teaspoon baking soda in a quart of water, add a few drops of liquid soap
to the mix to help it cling better to the foliage, spray infected plants
thoroughly. Another unusual remedy for fighting fungal diseases is
manure tea. This formulation fights blackspot, as well as mildew and
rust, while providing foliar nutrition. Place one gallon of
well-composted manure in a 5-gallon bucket and fill with water. Stir the
mixture well and let sit in a warm place for three days. Strain the
mixture through a cheesecloth or mesh and use the resulting tea to spray
disease affected plants (the solids left behind can be applied around
the base of the plants as added fertilizer).