last year I used mancozeb one week and banner maxx the next week, this is what I did most of the year and I had black spot kinder bad. I then tried Earth’s Ally and still had a lot of black spot. I live in Georgia and the summer are pretty hot and dry. I am wondering if my bushes have become immune to mancozeb. Need some help.
Mancozeb is a widely used and fairly effective fungicide. But it is non-systemic. I would suggest combining it with a systemic protection like BioAdvanced 3-in-1. Second, remember that we try to keep black leaf under control; it is impossible to eradicate it, particularly late in the season. I try to avoid all chemicals and work from the roots up, using soil with measures of dirt, compost, and very aged cow or horse (never chicken or dog) manure. I have found that my plants are so healthy that they can naturally resist most diseases. Good luck! John H.
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Mancozeb is a contact fungicide and lasts a week at most. If you want to get good control over blackspot, then combining Mancozeb with a systemic fungicide such as Myclobutanil or Propiconazole and spray immediately after pruning, and then every 10 to 14 days, depending on disease pressure. For example if there is a lot of rain, then you would need to spray more frequently. The BioAdvanced product is adequate, however, not concentrated.
Thank for the info but I found out yesterday while trying to order some Mancozeb that they have stop making it, Government has made them stop sailing it to the public, so when what is out there is gone that will be it.
That’s unfortunate but as Rosejoy has mentioned alternating every 1-2 sprays should be effective.
Another option you use to reduce the severity is feeding extra silica. It strengthens cell walls as well as stimulates defense responses.
A cheap way to get extra silica is by using potassium silicate otherwise you can use monosilicic acid. This may be fed through the roots or used as a foliar spray. If you use it as a foliar spray combine it with your antifungal.
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Fear not, you have other options, on Amazon, and it’s on sale, look at Manzate Pro-stick, 6 pounds. It is what I use. It is a powder, so you need to dissolve in water and stir or shake. I use a quart container to mix it. You only need 1 tablespoon per gallon. Keep it dry and it will last a very long time. Also look at Southern Ags Dithane M-45. And yes, Bonide’s Mancozeb is no longer being manufactured so if any of you see it a local garden center and want a very good contact fungicide for black spot, buy it.
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Like this idea, how often do you spray or drench this silica product?
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I mix it in with the liquid fertilizer I use every watering.
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can I use manzate with a electric spay pump
You will get better results combining the mancozeb with either Myclobutanil or Propiconazole. In cooler weather you can use Daconil instead of Mancozeb. Also if you have a lot of roses, including a generic Azoxystrobin which acts synergistically with the systemic fungicides.
can I use manzate pro-stick in a electric pump spayer
I have never used one of those sprayers. The powder does need to be dissolved in water first. Warm water is better. I use a 2 gallon pump sprayer and I have a Spot Shot 5 gallon battery powered sprayer. Do you have the instructions? Is it an Atomist sprayer? The instructions may discuss if you can use flowable powders.
I say electric but it is powered by rechargeable battery and since I see you have one I should be alright.
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I think you are correct thinking about fungal resistance with continued use. Rotation(Two or three products with different modes of action) will help the resistance issue. Talk to local Consulting Rosarians for products they recommend.
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Preventing blackspot is better than trying to cure. Before resulting to chemicals I recommend review your growing practices. Are you watering too late in the day? Are your roses planted to close together? Have you pruned your roses to open the center to allow good air circulation? When do you begin your preventative spray program?
Once you answer these questions, then you can start a chemical attack. I would recommend a regular 7-10 day program alternating fungicides to reduce the potential for building resistance. If your roses develop black spot I recommend spraying with a combination of mancozeb and tebuconazole on a 7 day basis for at least 4 weeks. Also remove all diseased foliage on the bushes and on the ground. Do not put diseased foliage in the compost pile.
Remember to read pesticide labels, follow label directions and use appropriate Personal Protective Equipment.
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Great advice and very helpful, however, even when we do the best horticultural practices, our hot, humid climate creates the optimal growing conditions for Diplocarpon rosea. At least now, we have so many more roses that are disease resistant. Growing exhibitions hybrid teas in our region is a challenge.