Why do you think it's losing it's effectiveness? If you only spray a few times a year, is it possible that you need to spray more often? Blackspot is dependent on the right weather conditions. If the conditions are right, you will get it if you don't spray at least every two weeks with the systemics. I use Bayer Advanced and also Honor Guard. HG you can get from Rosemania. There are many times I don't spray every two or even three weeks, but if we get the right conditions, the bs can come on very strong if I don't.

The active ingredient in Honor Guard is the same as Banner Maxx, and the ingredient in Bayer is very similar. If fungi are resistant to the one, they will be resistant to the other. I agree with Buford that you might just need to spray more often under some weather conditions. The typical advice for Bayer is to spray every two weeks if you want perfect control. This year I have controlled BS effectively by spraying only once a month, but it was very dry from May through August. Roses did get a lot of cercospora though, with a few eventually defoliated.

Maryl, I don't know if climate conditions vary a lot in Oklahoma--I know they didn't the few times I drove through OK--except the it got dryer the further west one goes, but here in Kansas (about 30 miles from the OK border), it is dry enough in July and August that I usually do not spray at all during that time period. It is also too hot here in July and August--BS doesn't do very well in extremely hot weather. I won't say my roses are perfect during July and August, but any spotting is quite minimal. I mention this because I know it gets at least that hot--if not hotter--in OK, so I would think that if you are having problems with spotting in the summer, it is more likely something like the cercospora Michael mentioned above. How often one has to spray for it, I don't know. Maybe Michael can give you more info. on that.

It's been years since I used anything except Bayer Garden Disease Control for Roses, Flowers, and Shrubs. My understanding is that one reason it is so effective is because it has a double-action effect, as it were--instantly killing BS spores and later as the systemic part circulates throughout the system, the longer term effect. (I know--not very scientific language--which just shows I'm not a scientist. ) I also keep a ready-mixed spray bottle of Daconil around for the occasional plant that has a few problems--I can zap it a couple times without having to mix up a bigger batch for many roses.

With Bayer, I spray a couple times in the spring when the temps are conducive to producing BS, and a couple times in the fall when the temps again return to the BS range. Again, that won't keep the roses perfect, but definitely keeps BS down to minimal problems.

Returning to weather, I don't know how gray and cloudy it was this summer in OK, but it certainly was--all summer long!--here in Kansas. That lack of sunshine noticeably reduced the re-blooming on my roses, and for me anyway, seemed to cause more BS problems--though I was in the hospital part of the summer so perhaps just fell behind on the gardening routines.

If some summers you need to spray a bit more in spring and fall, keep in mind that you may be able to skip sprayings during the (hot) summers.

Good luck.

Kate

You all may have hit on it. I guess I'm spoiled, but with my usual spray routine I seldom have much B.S. This year we had rain during a couple of normally dry months (July/Aug) and as per my usual practice, I hadn't sprayed. I quickly picked back up spraying at regular intervals, but a couple of roses continue seriously blackspotting even now that they are sprayed (with Banner Maxx). I've had other leaf spot diseases in the past when a cool spell passes through accompanied by rain or heavy dew during the summer months, but this is not that I'm pretty sure. It's just plain old unapologetic blackspot.......Since RRV has devastated the roses around here I've moved on to other plants, but would like to keep a couple dozen roses going if I can keep them relatively spot free. Wasn't there some conversation about Bayer Advanced Garden Disease Control "killing existing blackspot"? AND does anyone know the shelf life of Banner Maxx? .....Maryl

It's proven beyond doubt that tebuconazole (Bayer) kills existing blackspot within the leaf. And if sprayed within 10 days of infection, it will save the leaf. The same may be true of Banner propiconazole, but I don't know.

The link is to a brilliant dissertation by a Kenyan woman scientist.

http://hss.ulb.uni-bonn.de/2005/0541/0541.pdf

I am in zone 5b and I use bayer advanced every two weeks and it works very well for my hybrid teas...

The same author whose Thesis is cited by michaelg has this to say about treating your roses with hydrogen peroxide (H2O2).

" Interestingly, we found that treatment of rose leaves with ROS (H2O2) prior to fungal inoculation promoted plant defense response regardless of the isolate virulence based on protein expression pattern analysis, suggesting that ROS (H2O2) can be efficiently incorporated into black spot disease management."

http://www.sciencedirect.com/science/article/pii/S0981942810000094

The full paper is available from the author at:

http://www.researchgate.net/profile/Simeon_Kotchoni/publication/41412474_Microscopic_and_biochemical_evidence_of_differentially_virulent_field_isolates_of_Diplocarpon_rosae_causing_black_spot_disease_of_roses/links/09e41512229feed742000000.pdf

michaelg, what do find works best for controlling cercospora?

I use Bayer and I do not have blackspot. In Louisville,KY., blackspot can be rampart if not addressed. I am pleased with the Bayer Disease Control.

The Bayer fungicide is effective against blackspot, cercospora and anthranose. Plus powdery mildew, if you get that. I agree that if it's hot and dry in July/August, I cut down my spraying. But one cooler rainy day can cause a huge blackspot outbreak. If you can spray right after that, you can prevent it.

I live in a very high black spot area (the smoky Mts don't get their name from smoke). I grow a lot of roses that will get black spot in an instant if not sprayed. I start in early spring and don't stop until some time in Nov. I spray every two weeks. Four times with Bayer and four times with Banner Max. Back and forth all growing season. After I cut back my roses for the fall, the next spraying I add Manzate to my fungicide for a good kick to kill ANY fungus in the garden. I exhibit so I must have great foliage along with good blooms.

This had been a good discussion and I thank everyone ( and thank you especially Michael for the informative article). Since it's just two roses that seem to be having a hard time overcoming B.S. after the unexpected summer rains, I think I have a permanent cure for them - and it's an organic one that has worked on some of my past disease prone roses. The trash bin. But I will buy a bottle of the Bayer Advanced Garden Disease Control next spring and try it...... Still upset with Ortho getting rid of Triforene and replacing it with nothing that I can see. I never thought I'd live to see the day that the Ortho brand went almost defunct.............Maryl

Ken I learned my lesson this year. I heard repeatedly that in my part of the world that I didn't need to spray in July and August. So like the good little student I am I stopped spraying with Bayer the first part of July. Well I didn't get blackspot but cercospora took over in August. I am now back to spraying every two weeks and my foliage is just now starting to look good again. I hadn't thought about the need to switch off between Bayer and Banner Max though so I will give that a try next spring

Beth, see michaelg's first response.
Bayer and Banner Maxx are from the same family of fungicides, and will
have similar actions. You would want to swap in a contact fungicide (e.
g., Daconil/Chlorothalonil or Manzate) to go with the systemics
instead of switching between Bayer and Banner. And, keep up the regular applications.

The following was stated: "Still upset with Ortho getting rid of Triforene and replacing it with nothing that I can see. I never thought I'd live to see the day that the Ortho brand went almost defunct.............Maryl"

H.Kuska comment: Triforine is listed as a California Proposition 65 Developmental Toxin. http://oehha.ca.gov/prop65/prop65_list/Newlist.html

It is already banned in New York and the European Union.

You may find this California court document of interest:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&uact=8&ved=0CEoQFjAGahUKEwibpJPYssDIAhVLVT4KHTOGBwY&url=http%3A%2F%2Foag.ca.gov%2Fsystem%2Ffiles%2Fprop65%2Fsettlements%2F2006-00715S1668.pdf&usg=AFQjCNH-FlUi5LaQ_9suv79Gm1WxUw3iXw&sig2=aXB3NB15A94FKDI83r_haQ&bvm=bv.104819420,d.cWw

"Since 31 March 2004 it has been illegal to use or store certain pesticides. The ban was brought in by the EU to make sure that the pesticides available, continue to meet modern safety standards.

The chemicals that are banned are ammonium sulphamate, atrazine, dichlorophen, dichlorprop, dikegulac, lindane, malathion, paraguat, permethrin, resmethrin, simazine, tar acids, tar oils, triforine and 2,3,6-TBA."

http://www.rochford.gov.uk/sites/rochford.gov.uk/files/Pesticides_ban_-_home_and_garden.pdf

Diane: Thanks for reiterating Michael's point about the similarity of action of Banner Maxx and Bayer. However I don't think Banner Maxx claims to kill blackspot spores as does Bayer, so the action may be similar but not exact (Michael: any comments on the difference between the two and killing B.S.??)........ Also Banner Maxx users need to be aware of the fact that the label states that only 5.4 gallons of BM be used per calendar year. With my very rough math and the number of roses I had/have, I just converted that to spraying no more then 5 times a year with Banner Maxx. The danger of using it more than that can cause the product to become ineffective against disease. I hoped I have avoided that....... I know that alternating with a contact fungicide such as Mancozeb, which works differently on the plant then the systemics, is recommended. Eons ago I did that. But to be quite frank, walking around in a mandatory cloud of spray every 1 to 2 weeks became tedious after 15 years or so and I determined to spend more time enjoying my roses then defending them. That meant that the roses that I selected needed to pick up part of the job of defending themselves if a spray date was missed or delayed. However this philosophy has been predicated on the use of effective chemicals when I do spray. Since they are being withdrawn from the market at a regular pace now, and with few if any replacement alternatives being researched or offered, those of us who face increased blackspot pressure due to climatic conditions (as in the hot/humid south), may be offered less and less desirable rose varieties to choose from. ......Maryl

In my experience, Bayer's ability as a surface fungicide wasn't good, which is why I use manzate with Banner Maxx. My short experience with the Bayer fungicide gave me slightly worse results than Banner/manzate, so I don't use the Bayer fungicide often. Your mileage may vary.

That's interesting Diane about your experience with Bayer. I too used Bayer many years ago and was no more impressed with it then my BM, so I went back to Banner Maxx/Fungunex rotation. What got me in a panic was finding out that my ever faithful Fungunex was being forced off the market. Banner Maxx is a dud against Powdery Mildew in my experience and Fungunex (Triforene) was one of the best. At this point I don't know what I will do about alternating chemicals. The current problem of a couple of blackspot prone roses will be solved easily enough by chucking them out but I still need to keep the others healthy in the future. Of course with RRV running rampant around here, it may all be a moot point anyway...........Maryl

I'm not an expert in such things, but I feel the chances of resistance developing in a small home garden is slight. Resistance develops through a series of mutations, each of which is improbable, so it is more likely to happen when a chemical is applied on a vast scale in agriculture where trillions of fungi compete in the evolutionary lottery and resistant strains can quickly spread across a region where monocultures prevail. Therefore I have never practiced rotation of chemicals.

If you are looking for a rotation partner for a conazole fungicide (Banner or Bayer), the strobilurin fungicides are less hazardous than mancozeb or chlorothalonil (Daconil). Generally the strobilurins are not marketed in small quantities to the home gardener. However, you can get azoxystrobin (Heritage) at Rosemania. It is safe and effective against blackspot.

I get a lot more cercospora then anything else. I had been using the Bayer and it was not controlling it. After talking with a breeder, here on the forum actually, I learned that tebuconzole is not as effective on cercospora as it is is on blackspot. I started rotating different fungicides and finally got the cercospora infestation under control.

Michael: I'm doing some research on Heritage (Azoxystrobin) and coincidently enough it is a recommended product for the control of leaf streak in daylilies. I'm a daylily person and this product may well help with not only my roses but the occasional outbreak of leaf streak on my daylilies. A double thank you for that recommendation. Have you ever used it?.......James, what product did you settle on for your cercospora?......Kate: I'm thinking that some experimentation may be in order and so Bayer remains on my list. Your climate is somewhat similar to mine I think - just a zone away...and your spray schedule is similar to mine with spring and fall being when disease pressure is usually the highest. How does Bayer do on Powdery Mildew for you?...........Maryl

I'm not sure about powdery mildew, Maryl. It has never been a big problem here, so I just haven't paid attention. However, I may have new information to report to you next season. Several months ago I planted the polyantha climber Clotilde Soupert who is notorious for PM problems. She is growing like crazy and sure enough--a couple days ago I noticed she got some PM on the ends of some of her canes. I haven't sprayed it yet with Bayer Disease Control (I'm temporarily out of it), so I'll probably just cut off the ends of some of those canes--and wait til next spring to address the problem, if she still has it by then.

I'll be interested in hearing some of the results of your "experiments" also.

Kate

I haven't used asoxystrobin, but its effectiveness is shown in the PhD thesis I linked above. Plus it is considered a "reduced risk pesticide."

I'm not sure what the active ingredient is. the brand name was bonide. its the only thing I could find in our local stores besides the bayer. I know next spring I would like to identify about three different sprays to rotsate. that will give me something to reseatch over the winter.

What fungicides may be available in stores: Bonide Infuse, Bonide Mancozeb, Immunox (Immunox plus has an insecticide), Bayer Advanced Disease Control, and Daconil.

Bonide Infuse is propiconazole, same as Banner and Honor Guard.

Has anyone tried the ARS endorsed product called "GreenCure"? It is the old time remedy for Powdery Mildew of Potassium Bicarbonate in a standardized packaged form?........ 20 years ago or so a homemade recipe using Postassium Bicarbonate swept this forum and I tried it on a few of my roses for powdery mildew. Defoliated every one of my "test" subjects. They were right about no PM though. Reading the reviews on this Green Cure one person had the same defoliation experience while the rest had good to great results. They are also now marketing it as a Blackspot control (which I tend not to believe). Anyway, anyone tried it?..............Maryl

Strobilurins will take care of cercospora which conazoles are not very effective with. They will also fight blackspot but not as effectively as conazoles. Strobilurins seem not to be particularly effective against rose powdery mildew (as opposed to other powdery mildew fungi). If I lived in a climate where I would get lots of everything I would probably stop growing roses..

Like dublinbay, PM isn't much of a problem for me. In the years that PM has been rampant, I change the dosage of Banner Maxx from 1/3 T to 2/3 T for two applications. That's usually plenty to keep PM in check.

Thanks Diane. Never thought of increasing the dosage for Powdery Mildew as I am used to always using the least recommended. That's a good idea. For right now I still have a bottle of Fungunex (Triforene) and will conserve it as long as I can and use it only in early spring........Nik- thanks for the input. As for stopping roses altogether, well, that's a hard thing to contemplate - it may come to that for all of us eventually, but still it's not something I want to happen. As much as I value other easier care ornamentals (and I love daylilies in particular), none of them can quite measure up to the perfume of a big voluptuous rose bloom. I think until they carry me off to the funny farm, I'll try and grow at least a few of them for that alone ........Maryl

Immunox is effective against powdery mildew, but really needs to be sprayed every week to control BS in my climate.

Myclobutanil (e.g. Immunox) has little efficacy, if any (depending on the strain), against BS. Also, as a triazole, it belongs to the same mode of action group as 'conazoles' (e.g. tebuconazole) so no real sense in rotating these for resistance management. Since this is the case, one might as well mix the two when facing both PM and BS...

Although PM does not pose as much of a danger to a rose as BS, fighting it is more problematic in my experience. Reason is, it attacks new growth and there's lots of that during the growing season. You can spray one week but in a few days there will be lots of unprotected growth stemming out... Best defense against PM is not growing PM magnets and learning to live with a bit of it.

I wonder if strengthening the rose immune system against mildew with salicylic acid (aspirin as substitute) or hydrogen peroxide would be sufficient.

http://onlinelibrary.wiley.com/doi/10.1111/tpj.12966/abstract;jsessionid=226249B08282882EC8F4432DDFA8E74D.f04t04?userIsAuthenticated=false&deniedAccessCustomisedMessage=