Question
Black Spot
Hi again Lynette. After a few months of being a new rose grower i have what i believe is an infestation of Black Spot! I'm asking you to confirm what i already know is the case, but maybe...just maybe??? If it is black spot, am I correct in saying that i should clear up all the fallen leaves and remove the infected ones?? (and destroy them by burning?). I've read of a mix of baking powder and household detergent in a solution that works, do you agree that this is an effective measure? I have roseclear ultra concentrate, but it's going to get expensive to re apply this every two weeks! At the moment 3 of the 8 bushes in close proximity are exhibiting signs. The 3 other bushes i have are in a separate location about 3 metres away and are unscathed...so far. Many thanks for any advice, Mark
AnswerYour roses do have black spot fungus disease on them. I would clean up the leaves that are on the ground but do not take off the ones that are still on the rose bush. Roses need all the leaves they can get as that is their food factory. Taking rose leaves off any plant, considerably weakens the bush. Yes I know rose books tell you to do it, but that is another rose myth that hasn't died as yet. Roses do not die from this fungal problem, but it does weaken them as they loose their leaves and sometimes cannot go through a cold winter.
Black spot spores float around in the air and can be a few different strains depending where you live. Because roses have breeding backgrounds like like a human, some are prone to black spot and some are only prone to a certain strain. So one year the rose will get BS and the next year because it is a different strain floating in the air, it will be clean. My point is that you cannot ever cure BS only keep it under control. The spray you mentioned is horribly expensive and will only kill the spores that are on the rose so I understand from those who use it, last about a month. The only method that has proven to be effective in helping the rose fight this disease, is spraying the rose in the spring before the leaves are out with a dormant oil spray like the ones used on the trees. Instructions for using on roses are also on the package. Then in a months time do another spray, again before the leaves start as the sulphur in the spray can burn new growth. Baking soda and detergent will give you nice clean roses. The baking soda is supposed to make the leaves inhospitable to the fungal spores so they won't start to grow. Funginex is the second best chemical to use and you can get it in Orthos Rose pride spray. However one of the things they have found with the BS spores, is that they become immune to a spray so that means you need to get a different type in a few years time. But for now the Funginex will solve your problem. It will probably tell you on the label, but do not use the spray when the weather is hot. Go out in the evening when it has cooled off and use it then. However I have found that if a rose is prone to most BS strains, then nothing will help it and it is best to get rid of it as you will always have the problem.
