The Usual Suspect: Black Spot !!!!

eagleshadow(8b)February 15, 2012

I have had very good results generally growing roses, with the exception of a continuing fight with black spot.

The humidity is virtually 100% (well, almost :) ) year round, and that doesn't help things one bit. And like right now, it's been raining most of the day, with overcast skies, temps in the 60's, and there will be no sun to dry the plants; an almost guaranteed recipe for black spot.

I've seen many things recommended, and Bayer 3 in 1 is sounding better all the time, but in the past I've used Mancozeb, a variant of Compass, acephate (ant killer actually), and Banner Max.

I'm sure this has been addressed many, many times, but are any others here plagued with this problem ? And if so, how do you prevent and/or control black spot.

I've seen Compass advertised as the end-it-all, genuine product for black spot, but for what the stuff costs, I could practically purchase all new roses :) !!! ($450 ??!!).

As stated, I know this has probably been discussed to the Nth degree, but any advice or recommendations would be very much appreciated.

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mike_rivers(z5 MI)

I don't live in blackspot hades and I seldom spray fungicides at all, so the following isn't based on personal experience but it does summarize what I've concluded from a lot of reading, including people's experience on the Rose Forum:

1) Don't use combination products like Bayer's 3 in 1 (a fungicide, insecticide and miticide, all in one package). If you want a fungicide, spray a fungicide.

2) The Compass fungicide is trifloxystrobin. Bayer has obtained the rights to sell this under their label. Do a search for Bayer Armada and you can purchase 12 ounces of the same stuff as the old Compass for about $69 (Rosemania still sells the old Compass and their price is indeed $450).

3) Anyway, I have never been impressed by the published results for controlling Blackspot with trifloxystrobin. I think the two best fungicides for blackspot of roses, at present, are propiconazole (Banner Maxx is one source) and tebuconazole (a Bayer product).

    Bookmark   February 15, 2012 at 2:03PM
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saldut

I don't know where you are, but I have/had the same BS problem, here in central Fla. and for years drove myself up the wall trying to control it, I had mostly the standard Hybrid Tea and Modern shrub roses.... I kept reading on GW abt. the OGRs-Antiques and China, Old Teas, and Noisettes, and the Earthkind roses, and finally decided to switch-over to them.... well, I can tell you what a difference there is....most of the China roses get zero BS.. the Old Teas get a bit depending on which ones and some get none... the Noisettes get some BS again depending on which ones, but minimally.... and the Earthkind stay mostly BS free.... for 2 years now I no longer spray, and have found which of the Modern roses can take the 'heat', there are a few and they get some BS but still bloom even tho' they are pretty bare, and the ones that depend on spray to live are long-gone.... I love the Antique roses, they have a sweetness and charm of their own and some are always in bloom, it is a whole new garden now., minus the spray....sally

    Bookmark   February 15, 2012 at 5:04PM
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idixierose(z8b Coastal SC)

From a fellow Zone 8b Rose nut...

I get good black spot control using Banner Maxx, Compass and Pentathlon (manzate).

With each of these chemicals, there's a range of the amount to mix per gallon of water. For example, with Banner Maxx, the recommended amount is 1/2 to 2/3 teaspoons per gallon. I've found that using the higher rate gave better control of black spot.

I also use Bayer 3-in-1 granular treatment, especially on roses that I don't want to spray. I also use it on all of our HTs, once in early spring and again in mid-September, just for extra protection.

I tend a garden for an estate and my black spot tolerance is zero. I've used this spray plan for the past 9 years and it's worked well. I spray every other week, March through October.

Some people use lime sulfur as a late winter/early spring clean-up treatment. Personally, I don't like messing with the smelly stuff, but I do
clean the rose beds well in the spring to remove old leaves and put out fresh mulch. Right after pruning, I do spray the bushes with dormant oil to smother insect eggs.

Concerning fungicides, I'm obsessive-compulsive. As for pesticides, I use them on an as-needed basis. Patrol your roses looking for trouble makers.

    Bookmark   February 16, 2012 at 12:14PM
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zack_lau

I use Bayer Advance Disease Control. My next choice, based on what I've read, would be Bonide's Infuse. Immunox also works well, provided I spray every week. Immunox is also sold as Immunox plus--which contains insecticides I don't need.

    Bookmark   February 16, 2012 at 12:27PM
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seil zone 6b MI

Arrrgh! I hate that Bayer 3 in 1! I wish they'd take it off the market. Please, if you have black spot get a fungicide. The Bayer Disease Control product will work much better and you won't be throwing money away on an insecticide when you don't have a bug problem and you won't be killing beneficial bugs in your garden. Which, by the way, will only lead to a worse bug problem down the road! Besides that your adding fertilizers as well. Did you account for that in your regular feeding program? All in all it's much better to use a single product for what ever purpose it was meant for and not some cocktail you don't need.

    Bookmark   February 16, 2012 at 12:29PM
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trospero(8)

Banner Maxx is 100% effective as long as you start before disease takes hold.

    Bookmark   February 16, 2012 at 1:13PM
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dublinbay z6 (KS)

I agree with the above posts. A two-pronged attack is needed.

First of all, get rid of all your disease-magnet roses, and replace them with roses rated as highly disease-resistant. One of the posts above lists some antique roses that are lovely and especially thrive in Zone 8 and southern regions generally speaking. There are also modern roses that are rated highly disease resistant or "exceptionally healthy" (if you are looking at David Austin's beautiful shrubs). The one thing you will probably need to do is give up completely on hybrid teas--very few rank as highly disease resistant--in fact, maybe none of them do.

The second step is a rigorous fungicide program. I'm not from your region, so I can't say for sure, but based on what others have experienced, I'd say you may need to spray every couple weeks--all season long, possibly. It depends on how resistant your new disease-resistant roses turn out to be. At any rate, I also recommend Bayer Advanced Garden Disease Control for Roses, Flowers, and Shrubs (or some long name close to that--I keep forgetting the whole thing). There are probably others that work also, but my understanding is that the Bayer fungicide kills current BS infection and prevents new ones from forming. Not all fungicides perform that dual function.

DO NOT USE ANY OF THE BAYER COMBO PRODUCTS (2 in 1 or 3 in 1). There ought to be a law against them! Needlessly destructive to the environment!

Good luck.

Kate

    Bookmark   February 16, 2012 at 3:13PM
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