Black spot & slugs

jill_wingettJune 26, 2013

I'd appreciate any advice on dealing with my black spot & slug problems!

I'm in zone 5b, Indianapolis. My Don Juan climbers have a bad case of slugs & my Julia child's have black spot - round 2! I tried a variety of remedies for black spot, the Cornell treatment & corn meal dusting to no avail. I have 2 Julia child's about 3 ft apart, defoliated one & left the other. The one I defoliated has worse black spot now than the one I left the leaves on.

I'm beginning to see some cross in issues, minor black spot on the don Juan's & a few slugs in the Julia child's. is Bauer 3 in 1 my best solution for dealing with both issues?

It's starting to really warm up here (90s this week) but still raining a lot overnight. The foliage on my roses looks awful!! Please help : )

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hoovb zone 9 sunset 23

Bayer 3-in-1 has too much pesticide, very overpriced fertilizer, and a not very-effective-as-a-soil drench fungicide. A "convinience" product. If you must spray use the Bayer Advanced Fungicide. Slugs, are we talking rose slugs or slug-slugs that are like snails?

Slugs-slugs there's an iron phosphate product--Sluggo is one brand--that kills them, whatever excess remains becomes soil fertilizer for additional iron.

Rose slugs, alert squishing with gloved fingers can do it. Hard-sprays of water to the foliage undersides. Or just ignore until their season is done and the plant grows new foliage.

Long term, bs-resistant roses are your best choice.

    Bookmark   June 26, 2013 at 10:50AM
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dublinbay z6 (KS)

If you are going to spray for the BS, the best fungicide in my opinion is Bayer Advanced Garden Disease Control for Roses, Flowers, and Shrubs (that is the loooooong name of the fungicide hoovb was referring to). You have to get it at Lowes or order online. You will also need to buy a 1 gal. hand-pump sprayer container--about $20 at Home Depot and such places. Follow directions carefully.

If you have rose slugs, most of us just pick the tiny tiny green "worms" off the leaves and either squish or toss them out into the grassy yard. In a week or two, predators will come along and gobble up the rest of the rose slugs, so you don't really need to do much of anything else.

And, yes, in the future buy BS-resistant roses. Makes life a lot easier. : )


    Bookmark   June 26, 2013 at 10:58AM
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michaelg(7a NC Mts)

[edit--Sorry for the repetition, cross-posted with Kate]

hoov's advice is good. The full name of the fungicide she mentioned is Bayer Advanced Disease Control for Roses, Flowers, and Shrubs. It contains only tebuconazole. Each application is highly effective for two weeks. You may find it at Lowe's or may need to order online. If you don't want to use synthetic pesticides, ask here about blackspot-resistant varieties for your area. Roses that defoliate repeatedly during the summer are liable to die during northern winters.

This post was edited by michaelg on Wed, Jun 26, 13 at 11:12

    Bookmark   June 26, 2013 at 11:03AM
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I rose freind of mine put me onto Mancozeb as the best control for black spot. It can be hard to find but do a web search to locate it. It will leave a whitish spotting on the leaves which can be washed off with soap and water when taking a cut flower into the house or for exhibition, but it works. You will need to remove all foilage that has any sign of black spot, and continue a spray routine but it works. Another product is Pentathlon DF. It is a powder that you have to mix with liguid and can get messy. Good luck.

    Bookmark   June 26, 2013 at 2:11PM
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Thanks everyone! I bought the JCs because they are supposed to have excellent disease resistance & AARS says they are one of the best roses for the Midwest. I didn't have any trouble with them the first 2 years, but this year they're in bad shape . I'll pick up some Bayer Advanced Fungicide & start squishing the rose slugs (yuck!)

    Bookmark   June 26, 2013 at 5:24PM
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nickl(Z7a NJ)

"... I bought the JCs because they are supposed to have excellent disease resistance..."


You have to understand that when a floribunda, climber, or most any other garden rose is considered 'disease resistant', it does not mean the same thing as what it means for Home Run, the Knock Outs, and the other disease resistant shrubs.

The latter roses have never been observed to get black spot, period. Ever. They were extensively tested for disease resistance.

The resistance of the former group is based more on general characteristics than on any kind of testing. .They will resist black spot in some years and under some growing conditions, but in bad years and/or under generally unfavorable conditions, they will get it.

    Bookmark   June 26, 2013 at 6:19PM
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jerijen(Zone 10)

It is my understanding, however, that in some places, KOs are beginning to show up with blackspot. There are very few absolutes in nature. :-)


    Bookmark   June 26, 2013 at 7:05PM
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I am very disappointed that no one has mentioned the potential dangers/precautions that they personally use/are aware of when applying the fungicide sprays that they have recommended.

Here is the 2012 summary of "Evaluation of tebuconazole, triclosan, methylparaben and ethylparaben according to the Danish proposal for criteria for endocrine disrupters, May 2012"

"Table 2 Proposed criteria for EDs Category 1- Endocrine disrupter Substances are placed in category 1 when they are known to have produced ED adverse effects in humans or animal species living in the environment or when there is evidence from animal studies, possibly supplemented with other information, to provide a strong presumption that the substance has the capacity to cause ED effects in humans or animals living in the environment. The animal studies shall provide clear evidence of ED effect in the absence of other toxic effects, or if occurring together with other toxic effects, the ED effects should be considered not to be a secondary non-specific consequence of other toxic effects. However, when there is e.g. mechanistic information that raises doubt about the relevance of the adverse effect for humans or the environment, Category 2a may be more appropriate. Substances can be allocated to this category based on:
- Adverse in vivo effects where an ED mode of action is highly plausible
- ED mode of action in vivo that is clearly linked to adverse in vivo effects (by e.g. readacross)"


Later in the report: "Among the 4 substances, tebuconazole and triclosan are categorized as EDs in category 1...."

Here is a link that might be useful: DANISH CENTRE ON ENDOCRINE DISRUPTERS 2012 Report

    Bookmark   June 26, 2013 at 10:32PM
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Thanks everyone! I'm aware that no rose is completely disease free & that there are consequences to spraying.

I really appreciate those of you who took the time to answer my actual question, "what's the best way to deal with both rose slugs & blackspot?"

Happy gardening!

    Bookmark   June 27, 2013 at 7:37AM
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nickl(Z7a NJ)


Do you have a reference to black spot infestation being observed on Knock Out roses? We have been growing the original Knock Out essentially since it was first released and at most have seen only a few insignificant spots on the foliage - nothing that I would call an actual BS infestation.

The same is true of our other roses in the same family, although of course we haven't been growing them nearly as long.

This is an area of high disease pressure for BS, so if it was going to happen anywhere, I would expect to see it here.

The Knock Outs do get mildew - in fact, they seem to be quite susceptible to it. At least two of the growers who called me last year to check out the "black spot" on their Knock Out roses actually had mildew. .So I'm assuming others had it, too.

    Bookmark   June 27, 2013 at 2:36PM
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michaelg(7a NC Mts)

KO is susceptible to cercospora disease, and most people can't tell that from blackspot. I've seen it make KOs look pretty bad. I have never seen a significant BS outbreak on KO. You might find a spot on a senile leaf here and there.

    Bookmark   June 27, 2013 at 3:04PM
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