Question about spraying

11 years ago

i would appreciate any advice I can get, but let me start by asking, please don't turn this discussion into arguments about spray v.s. no spray. There's plenty of that on other threads. My question is, can Bayer advanced disease control be mixed with liquid concentrated seven in the same application for spraying. I was told that mixing those won't cause either to not be effective, but now I'm not sure. I spray my roses with the Bayer about every two weeks and even if I get a little black spot at the end of the season, it's usually not that much. I went out today to find that some of the roses have more black spot than I usually get, especially my great maidens blush. I follow pretty smart watering and feeding regemins and only water in the mornings, trying not to create any situation that would promote fungal diseases. I am in Indian zone 5b and I thing it's probably just a product of our unpredictable weather. In any case, any advice would be appreciated. We can have harsh winters here and I've learned that the best way for a rose to survive the winter is by going into it as healthy as possible.

Featured Answer

henry_kuska

11 years ago

Perhaps your fungus is mutating to tolerate the mode of action of your fungicide.

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Comments (8)

michaelg
11 years ago
What are you using the Sevin for? A caution--use of Sevin can cause outbreaks of spider mites on roses. It can also burn foliage moderately in hot weather.

I don't think tank-mixing would affect the chemistry of the tebuconazole fungicide, but I don't know for sure.
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James Hawes
Original Author
11 years ago
I didnvt know that about the spider mites. I use the sevin to control japanese beetles, grasshoppers, and leaf hoppers. I get a lot of those here.
I thought about immunity to the same fungicide. Maybe I should probably alternate fungicides.
michaelg
11 years ago
Another possibility is that your spots are cercospora rather than blackspot . Tebuconazole doesn't control cercospora as well. I have never heard of tebuconazole resistance developing in a home garden. It's possible though.

When you tank-mix, don't double the water.
henry_kuska
11 years ago
Regarding cercospora, see: http://www.rosebreeders.org/forum/viewtopic.php?f=2&t=55157

(thread goes over several pages)
James Hawes
Original Author
11 years ago
Thank you for the info Henry. The link was very educational. the pictures of blackspot vs cercspora show me that it is cercospora I've been dealing with. I've never distinguished between the two. now I judt have to fimd the best application to fight the cercospora.
Lavender Lass
11 years ago
I will not mention the S word, but if you have more birds and beneficial insects...that might help with some of your issues. I never (S word) and we haven't had any problems. And we have zone 4 winters :)
nikthegreek
11 years ago
last modified: 11 years ago
'now I judt have to fimd the best application to fight the cercospora'

Synthetic fungicides containing any drastic ingredient in the class of stobilurins (e.g. pyraxostrobin, azoxystrobin, trifloxystrobin etc), don't let Henry know I told you about it, or copper based fungicides if you want to be somewhat more 'ecological' and a quite bit safer yourself. Can't help you with specific brands since I'm not resident in the US but over here Cabrio, Switch and Flint would fall in the first category (the same would fight botrytis blight also). Best method (regardless of health concerns and the like) would be to alternate between strobilurins and copper. Disclaimer: A bit of fungal disease should be acceptable to anybody growing roses in his/her garden in my view. So use sparingly.