For example, Morden Sunrise is what I call a “blackspot
magnet”. I loved the color of that rose
and planted several in a cluster in one of my terraced beds, several years
ago. The first summer they were covered
with blackspot and almost immediately every other rose around them, including
disease-resistant Buck roses on which I’d never seen blackspot, became infected
as well. So I had no choice other than
getting out my fungicides and spraying the whole garden periodically for the
rest of the summer; something I really don’t like to do as an organic
gardener.
So, lesson number one in controlling blackspot is to find
out which roses are most susceptible and, either don’t plant them in the first
place or, if you already have them, shovel prune them like I did with Morden
Sunrise. In my opinion, there are so
many great, disease-resistant roses that there really is no justification for
growing susceptible plants and polluting your garden (and neighborhood) with
fungicides. The Buck roses, for example,
are beautiful and quite disease resistant.
That’s what Dr. Griffith Buck’s work was all about: hybridizing
beautiful, disease-resistant, winter-hardy roses. He was phenomenally successful and we are
heirs to his legacy. This lesson is an integral part of practicing Integrated
Pest Management (IPM), which all of us should be doing, for our own health, as
well as the health of those around us.
Lesson number two is, if you have roses that are susceptible
to blackspot and you just can’t part with them (yet), or if you have an
outbreak on your resistant plants that you need to fix, be sure to use the
right fungicide and practice IPM, which means that you must spray only the right
fungicides and spray them as infrequently as possible.
So, what are the right fungicides and how often should you
spray them? Fact: To my knowledge, there is only one fungicide
that actually KILLS blackspot spores; and that’s Manzate (also known as Mancozeb). So, if you are going to spray for blackspot (and
most of us will have to spray at least once in a summer), get yourself some
Manzate. It’s available on-line at
Rosemania.com and the shipping is free.
I find that the liquid product is easier to use than the wettable
powder, albeit a bit more expensive. To
the best of my knowledge, all of the other products labeled and sold for the
treatment of blackspot are fungus inhibitors, not killers.
The late Howard Walters, past president of the American Rose
Society, wrote a wonderful column known as “Rosarian Ramblings” in the American Rose for many years. One of his favorite subjects was treating
blackspot and he always recommended using Manzate, which is a surfactant, in
combination with Banner Maxx (Propiconazole), which is the best systemic inhibitor (also
available at Rosemania.com). The combination of the strong inhibitor with the
proven killer is a one-two, knockout punch, which allows you to spray only once
every two or three weeks, depending on how bad your infestation is. Using Manzate alone would require weekly
spraying, until all spores were killed. In my garden, where blackspot occurs
only once or twice in a summer, the Manzate/Banner Max (Propiconazole) combination does the
trick in only one or two sprayings for the whole summer, which is good IPM.
Now, let’s look at another fungus, spot anthracnose,
which I have found to be more deadly than blackspot, in that it will take out
an entire rosebed, if left uncontrolled.
A lot of people mistake it for blackspot, even though it really doesn’t
look much like it. It’s important to
recognize anthracnose before it does irreparable damage in your garden. Fortunately, the treatment is exactly the
same as for blackspot, i.e., Manzate and Banner Maxx (Propiconazole) so mistaking it for
blackspot is usually not fatal, as long as you spray it a couple of times. Here are two good pictures of spot
anthracnose:
Last but not least, let’s talk about powdery mildew. Banner
Maxx (Propiconazole) inhibits powdery mildew but Manzate does nothing. Fortunately for us
IPMers, powdery mildew can be controlled, without a fungicide, by using strong
doses of baking powder. Just mix three
tablespoons of baking powder, per gallon of water, spray it on several times
over a few weeks time, and powdery mildew usually goes away. Another little-known fact is that powdery
mildew doesn’t like to be wet, so you can give your roses a good washing before
applying the baking powder mixture.
Unfortunately, if you are also fighting blackspot or anthracnose, washing
your roses (or top watering) isn’t the best idea.
Finally, and this is more important than anything else I’ve
said here, you must wear protective
equipment and clothing when spraying fungicides (and insecticides). First and foremost, use a respirator so you
don’t breathe any of the chemicals. Paper dust masks just don’t cut it here (if
you can smell it, you are breathing it into your lungs). I wear a full-face 3M
respirator, which is preferable, but partial-face respirators will work, if you
also wear protective goggles. Check out
3M’s website for their respirator products and where you can buy them: http://solutions.3m.com/wps/portal/3M/en_US/PPESafetySolutions/PPESafety/
I also recommend
wearing inexpensive Tyvek coveralls (also available at Rosemania.com). These can be hosed off and dried in the sun after
each using, so that one or two sets of coveralls will be enough for a whole
summer of spraying. Also, wear
protective nitrile or rubber gloves for both mixing and spraying chemicals. I wear nitrile “milking” gloves sold by Fleet
Farm, but any medical/surgical glove will do.
And…It should go without saying that if you get any of this “stuff” on
you, go wash it off!
