Black Spot

kazziemt

Hi peeps, I have a standard rose that suffers from black spot, I treat it regularly but still the spot returns and the leaves drop off, is there something else I am doing wrong?

edhelka

If you treat it regularly with a fungicide (every 14 days or according to the instructions) you can't do much more. Remove all infected leaves as soon as the spots appear and make sure that the rose has good airflow around its leaves. You could also rotate several brands of fungicide because blackspot can evolve to be resistant to some fungicides.

Bijdezee

Also, remove all fallen leaves in the autumn. I find that mulching with a thick layer of well rotted manure really reduces the fungus from staying in the soil and starting again in spring. I rarely have to spray mine now. 

amancalledgeorge

If you get persistent blackspot especially in newer cultivars is just an indication of inappropriate conditions...you need to make the plants healthier so they have better resistance to disease. Spraying is just treating the symptoms not really improving the long-term health of the plant. 

kazziemt

Thanks peeps, the rose was taken from a pot after becoming root bound and planted into heavy clay soil, would I be best repotting it do you think?

foxwales

Yep, repot.  A healthy plant with good soil and conditions will do better at fighting off disease.  

Butterfly66

@kazziemt don’t move it again. It’s probably still settling in and recovering from been pot bound. Roses usually like clay soil as it’s full of nutrients. Make sure it’s well watered until it settles in and remove all the leaves with black spot - don’t compost them at home as the spores will survive. The rose should releaf and hopefully they will be clear.
A mulch in spring and Autumn with home-made compost and/or composted manure will Help keep it healthy.

I don’t think it’s possible to ever be completely rid of blackspot but keeping roses healthy means they are less susceptible and/or suffer less.

BobTheGardener

Some varieties are far more prone than others (this is due to the breeding processes of the past concentrating on selecting for blooms rather than overall plant health) so it's often more trouble than it's worth constantly fighting the disease on such cultivars.  Obviously, local growing conditions are also a very large factor but if other nearby roses are unaffected, it is seriously worth considering removal and replacement with another less susceptible cultivar;  Sometimes you just have to accept that many rose cultivars have weak immune systems and are not capable of looking after themselves in anything other than ideal conditions.