Below is what the dead leaves look like The still alive ones are all green and those grey spots on them
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Are there any small black dots on the surface? Also, on the back of the leaves is there anything else, whatever the colour, besides the black venation? Other parts of the plant are also affected (stems, petals), different colours, patches, deformities, anything unusual about the plant? I'm very curious :) Update - the small white dots in the picture are holes, dots, or light reflecting when taking the pic?– AlinaJul 20, 2017 at 12:02
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the back of the leaf does not seem to be affected. I am seeing something similar on my hostas. No flowers on this affected plant, the stems are OK> Another rose near by is presenting the same sympthoms. Due to some reno projects I have not cut my grass for three weeks and it is quite high. Hostas seem to be affected by something as well (leaves are like perforated by acid rain )– MiniMeJul 20, 2017 at 12:18
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Also could you provide some information on the location of the plant, in a pot or in the ground, whether it receives any sun and for how long, whether it is sheltered or exposed to wind?– andrewbuilderJul 20, 2017 at 18:16
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close to a fence, this one is a climbing rose which I would like to grow to cover the fence and go higher than the fence. It gets full sun between 11AM and like 4-5PM in the afternoon, in ground plant, not much wind– MiniMeJul 21, 2017 at 2:07
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2 Answers
Black spot is a common fungal problem on roses almost everywhere that roses will grow, they are very susceptible to it. In the UK, we spray fortnightly with something like Roseclear Ultra, which contains a systemic fungicide, from leaf break until leaf fall in an attempt to keep it at bay. Without such a regime, roses generally succumb, unless you've been clever enough to pick black spot resistant varieties (Kordes bred ones are the most disease resistant).
Clear up fallen leaves as soon as you notice them,and clear away all leaf debris before winter to clear away overwintering spores. Find a fungicide product in your area that will treat this infection. Other things that help are correct pruning to promote maximum air flow around the branches, no under planting other than with ground hugging plants,planting in full sun, feeding with a specialist rose food as often as recommended, and mulching with composted manure. These last two recommendations are simply to help the plant have more strength to resist by providing optimum nutrition.
You mentioned your Hostas having 'perforated' leaves. Hostas are a favoured target for slugs and snails, so if you don't use slug repellent/killer products from early in the growing season regularly, holes in the leaves are inevitable.
It looks like Black Spot to me. A very common problem with roses here.
