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Graham Thomas and blackspot
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Posted by
t-bred 5 (
My Page) on
Wed, Oct 3, 12 at 12:02
| Is GT just really prone to BS? Mine is a small (18") plant that I rooted this summer and planted out in Aug. It is growing very well but this one blackspots like crazy! I purchased the Bayer disease spray- does nothing! Got out the Daconil this morning to see if that does anything. Never had one this bad! Anyone else experience this? |
Follow-Up Postings:
RE: Graham Thomas and blackspot
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| When your GT gets somewhat bigger and stronger, it might be somewhat more vigorous about resisting disease. If it was planted in Aug., it hasn't really had time to settle in and develop a good root system yet, plus autumn (as the temps cool off a bit) tends to be prime BS season, so it really isn't a good measure of GT's year-round performance, particularly as it gains maturity. On the other hand, it is not unusual to find posts on this forum complaining that GT is not very disease-resistant. I might add, if Bayer Garden Disease Control for Roses, Flowers, and Shrubs doesn't work effectively on a rose, then probably nothing will. If the BS is really bad, it may take several sprays (10 days-2 weeks apart) for the spray to be completely effective. However, the leaves that already have spots will still have spots--no spray makes the spots invisible. About all you can do with the already-spoiled leaves is pull them off and throw them away. Good luck. Kate |
RE: Graham Thomas and blackspot
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| Thanks Kate! I've actually been spraying it closer to every 10 days than 2 weeks, just frustrating that the new growth is affected almost immediately regardless of being sprayed. I have removed the worst affected leaves near ground level,nothing seems to slow it down. I do hope that maturity will assist with some resistance for this one! |
RE: Graham Thomas and blackspot
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| I have the same experience with another Austen, Abe Darby. I rooted a cutting this summer from my 2-year old Abe Darby, and the "baby" is about 5 feet away from the mother plant. While so far the mother plant has only dropped some of lower leaves, the baby is completely infected. I don't spray. So there does seem to be some truth to what Kate mentioned above re: maturity and blackspot resistance. |
RE: Graham Thomas and blackspot
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| Are you using Bayer Disease Control with only tebuconazole, or Bayer Natria, which is a microbial product? The former is the most effective blackspot control on the market. Are you sure you are mixing correctly and applying thoroughly? The only other explanation I can think of is that spray doesn't cling to the newest leaves. Spraying every 7 days might be needed until the disease is under control. If you are using Bayer Natria, that can't be expected to do much against high blackspot pressure. |
RE: Graham Thomas and blackspot
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| That's interesting Farmerduck, I guess we can root these things but can't grow them!!?? Frustrating! Michaelg, it is the Bayer with the tebuconazole, been spraying tops and undersides of leaves. I did have a post recently that I had inquired about the prepared life of fungicide because it doesn't seem to be doing the job. Double and triple checked the dilution ratio and all is correct, not sold on the Bayer product. I have kept Daconil on hand for years to assist with the septoria that my tomatoes suffer yearly, I know it's not ideal for roses in the heat but I'll give it a try in the cooling temperatures. |
RE: Graham Thomas and blackspot
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| I would not be surprised if the tebuconazole is too much for the young root - mycorrhizae formation. |
Here is a link that might be useful: Effects of Pesticides on the Growth of Ectomycorrhizal Fungi and Ectomycorrhiza Formation
RE: Graham Thomas and blackspot
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- Posted by TNY78 7a-East TN (My Page) on
Wed, Oct 3, 12 at 21:22
| Interesting. I purchased by GT earlier this summer as a one gallon from Two Sisters. It came out of the box in beautiful condition, but since I've had it, it just grows leaves and drops them due to BS. I haven't put him in the ground yet, but maybe once he starts to establish himself, he'll do better like Kate said...hopefully :) Tammy |
RE: Graham Thomas and blackspot
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| I have two enormous Graham Thomas roses in my yard and I've never seen a spot of blackspot on them. I do spray every 2-3 weeks, but if I'm running short on material, I skip these two. Maybe once your plant gets bigger it will have better resistance. |
RE: Graham Thomas and blackspot
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- Posted by seil z6b MI (My Page) on
Mon, Oct 8, 12 at 20:37
| Give it time. My GT was slower to take off but is mammoth now. However, it does still black spot with the best of them, lol. |
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