This is a shrub rose Abraham Darby. I bought it this spring and have been growing in a container. It's been blooming, and looks healthy overall. But I noticed that leaves have changed the even green color. They look blotchy, and on the back side of the leaf there is some kind of a greyish web or deposit. Is this caused by a virus or insects?
Hi gallina. Others may have different opinions but a greyish web or deposit on the back of a leaf sounds to me like grey mold or Botrytis--so a fungus.
I just took the leaf to the nearest nursery, and they said it was milldew. They recommended a sulphur-based spray. I did not buy it, because the rose is on my balcony, I don't want the smell around. Are there any other options for the milldew?
For mite control try Safer's Insecticidal soap. Make sure you hit the insect with it. You can also try lime-sulphur. Or a mix of the insecticidal soap and the lime-sulphur. Read the bottle directions. Other remedies are lace wings, lady beetles and there are predatory mites too.
It's not a matter of mites being rare here, it's a matter of bad information being common at retail outlets - if the number of "the nursery said" internet posts relating falsehoods or misdirections are any indication. Nowadays often "the nursery" is a big box chain store plant department.
I'm surprised that the specialist at the nursery (one of the biggest in Toronto) gave wrong information.
I've found that the nurseries hire alot of inexperienced people that they can pay lower wages to. Up here they should at least get their pesticide applicators license and become certified through the Canadian Nursery Landscape Association. If you're a retail nursery person, look into the C.H.T. Certification. That is, Certified Horticultural Technician.
