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The moist conditions and mild nights interspersed with a few dewy nights has seen
Powdery Mildew spread wildly over the past week. That’s the white powdery like
substance on the leaves in case you are unfamiliar.
Powdery Mildew is fungal disease and at it’s worst needs to be controlled by
spraying a systemic fungicide such as Bayleton®. Mild infestations can be controlled
using Mancozeb® or water-soluble sulphur can be sprayed in warm weather. The soapy
alternatives can upset the soil pH.
You can also be more selective about the varieties of Rose you plant. The old
winter-flowering variety "Lorraine Lee" is notoriously susceptible at this time
of year, as are some of the old China Roses, such as ‘Sempervirens'. Modern Hybrid
Teas and Meidiland® Landscape Roses are not nearly as prone to fungal diseases in this
area.
I have found unusual fungal control using PestOil™, which is supposed to be for
control of scale, but it leaves a fine film of synthetic oil over the foliage, that drives
thrips away, seems to send mites over the fence and surprise, surprise seems to control
fungal diseases too. It’s probably the most effective benign control you could use
for fungal disease and it’s not even registered for that!
Annie started feeding her Roses this week. That’s got to be a sign. She takes my
advice religiously, so I must have told her on this day some time ago, that it’s time
to feed the Roses. Anyhow they got a slow release and some potassium sulphate. Those tiny
buds will never have had it so good!
On feeding Roses, it’s a waste of fertilizer to spread it around more than the
width of the pruned canopy, because the root run of a rose is not that extensive. Also if
you are growing annuals under your Roses they need twice as much fertilizer or feeding
weekly with such competition down under for that nutrient.
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