Gardening Questions: Sooty mildew??

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ryduj Spring, TX December 29, 2007 2:12 AM	While I was putting up Christmas lights this year, I noticed that the crepe myrtle in my front yard is covered in a black ashy looking substance. It's also on a few of the surrounding plants around the crepe myrtle. After researching online, I think it might be this sooty mold or whatever...what would you suggest to try to get rid of it? The poor plant (which was lovely in bloom this summer) is literally covered almost completely in it. I'm just afraid that it'll inhibit proper photosynthesis once the new season starts up if I don't get rid of it. Any suggestions? Thanks!
mistygardener Saint James, MO (Zone 6b) December 29, 2007 2:17 AM	Hi there! It is called powdery mildew and you can buy a spray to take care of it at Lowe's. The name of the product escapes me at the moment and I have no clue where the bottle is. You will definitely want to get rid of it, cause if I am not mistaken it can kill your tree. We have several CM's planted around the yard, and wouldn't ya know both varieties gets it! I found the bottle! It is made by Spectracide-Immunox Multi-Purpose Fungicide. I bought the concentrate and it was around 12 or 13 bucks for a 16 ounce bottle. Good luck with your CM's cause they sure are lovely trees!
plantfreak78 Rolesville, NC (Zone 7b) December 29, 2007 1:33 PM	Actually, the problem sounds more like sooty mold (which is typically black) than powdery mildew (which is typically light gray and fuzzy). If you try to scrape the substance and it kind of flakes off, it's definitely sooty mold. The reason it matters is that powdery mildew is caused by a fungus and must be treated with a fungicide. Sooty mold occurs when insects such as aphids suck the juice out of the leaves and poo it out again. The mold forms on that poo (called honeydew) :) If that is the case, you will need to treat the plant with an insecticide (I would use Isotox, made by Ortho) to kill the insects. There is no direct cure for sooty mold.
ecrane3 Dublin, CA (Zone 9a) December 29, 2007 1:47 PM	I agree, it's sooty mold which probably originated from an aphid infestation this summer. Since the aphids are most likely gone for the year and since Crape myrtles are deciduous, I wouldn't bother doing much of anything at this point. When the leaves fall off, I'd rake them up and get rid of them, and then next year make sure you're on the lookout for aphids so that you can catch them early before they cause the problem again. Crape myrtles tend to be aphid magnets so you do need to be vigilant or else this could happen over and over every year.
WeeNel Ayrshire Scotland (United Kingdom) December 29, 2007 3:39 PM	Once you gather up all the leaves, burn them as by now, this problem will have weakened your plant to an extent, it is then open to lots of other diseases, make sure your plant gets plenty water and feed, usually healthy plants can put up with a little of this problem, however, if you loose all your leaves to this trouble, the plant can become week, also as Ecrane said, make sure you are way ahead of the aphids nest spring summer and deal with them before your plant gets infested again, good luck. WeeNel.
ecrane3 Dublin, CA (Zone 9a) December 29, 2007 5:36 PM	Actually sooty mold is really just a cosmetic issue, the mold is growing on the honeydew that aphids secreted on the leaves so it's not taking energy from the plant. If there's enough of it and it's covering enough of the leaves then it could interfere somewhat with photosynthesis, but since crape myrtles are deciduous and it's going to be losing its leaves and going dormant any day now I wouldn't worry about that at this point. And sooty mold can't re-infect the tree the following year if you leave the leaves around the way that fungal diseases can, that's not the way it's spread. When the leaves do fall off I'd rake them up and throw them away because they're ugly and sticky, but it's not necessary to burn them. The only way the sooty mold will come back next year is if the aphids get out of control again, and if the aphids get out of control you'll end up with the problem again regardless of what you do with this year's fallen leaves.
pbyrley Wake Forest, NC (Zone 7b) October 11, 2008 9:42 AM	Thanks ecrane3, That was just what I needed. My sooty mold wasn't severe, but I thought Volck oil was the treatment - maybe it discouraged some aphids because I didn't see any of them afterwards. I'll get on their case early next year. Paul
kitten0115 La Vergne, TN October 11, 2008 5:53 PM	Another thing to check is to see if you have , say, a hackberry aaround. What I have noticed is that CM don't get too many aphids but what usually happens is that other trees around them do, drop their honeydew a and sooty mold attaches to it. Look for the real cause of the aphids I have seen ones completely black this year because of the wooly hackberry aphid whaich have jumped in numbers.
pbyrley Wake Forest, NC (Zone 7b) November 3, 2008 10:46 AM	Does anyone know if a systemic like Bayer 123 would be ok for keeping the aphid/sooty mold at bay AND not kiiling the bees which are sometimes visiting the crape myrtle flowers? I'd rather not kill bees than have a sooty mold free crape myrtle. How about other aphid solutions? Isn't Ortho also a bee killer? I guess I should be asking what is a non persistent aphid killer? When I was a kid, farmers threw their cigarettes into a large crock of water (nasty!) to make a free version of Black Leaf 40 - is that still available? Paul
JuneyBug South Central Ozarks, MO (Zone 5b) November 3, 2008 2:56 PM	A tin of snuff has lasted me YEARS! I put some into a quart of water and then when it has steeped enough, I strain it into a small sprayer. Do not use systeimics on flowering plants.
ecrane3 Dublin, CA (Zone 9a) November 3, 2008 5:14 PM	I don't think it's been conclusively established one way or the other the effect of the systemics on bees. There had been some studies a while back linking it to colony collapse disorder; I think that's been disproved now but even if it doesn't cause CCD I don't think it's been proved that it doesn't have any negative impact at all on bees, so I'd probably go with something else just to be safe. Insecticidal soap works well on aphids and is fairly benign otherwise. Only trouble with it (or any other non-systemic) is that you'll need to repeat the treatment--any one aphid that you miss the first time around will reproduce quickly and become thousands again if you don't keep after them. Given the time of year and the fact that crape myrtles are deciduous I wouldn't bother trying to do anything about the sooty mold since the leaves will be falling off soon, just try to get on top of the aphids a little earlier next year and then you won't wind up with the sooty mold.
pbyrley Wake Forest, NC (Zone 7b) November 8, 2008 9:43 PM	Thanks nanbernier and ecrane3 - I felt the systemic was probably a bad idea and I'd rather have a little sooty mold than kill some bees. Glad to know the insecticidal soap is good for aphids (or bad for aphids from their viewpoint). I will feel much better about using that and repeating won't be a problem for me. And snuff can always be my second line of defense. I check my plants often so will look for aphids more diligently next year. BTW, do you know if the insecticidal soap work on those orange things, Milkweed Bugs (Oncopeltus), that get on the milkweed plants. I would be sure the monarch cats haven't arrived before spraying. Thanks so much for the info and advice. Paul
ecrane3 Dublin, CA (Zone 9a) November 8, 2008 10:19 PM	I've found the milkweed aphids to be more persistent than the others--the insecticidal soap still kills them, but they seem to either reproduce faster, or else new ones find the plants quicker. Someone on another thread mentioned that they squish the mikweed aphids by hand and leave the squished bugs on the plant and that deters more from coming.
pbyrley Wake Forest, NC (Zone 7b) November 10, 2008 1:34 PM	ecrane3, I had googled Oncopeltus and found that these are not aphids at all; they are larvae of the "milkweed bug". Here is a picture of the adult beetle. I had also been squishing them with my bare hand and washing my hands quickly, but it probably is a bad idea as the bugs (incl larvae) that feed on milkweed are poisonous. I have some vinyl gloves left over from epoxying that I will use next year if the soap fails. View Larger
ecrane3 Dublin, CA (Zone 9a) November 10, 2008 4:19 PM	I think we're talking about different bugs--I hadn't noticed the reference to milkweed bugs, and since this thread was about aphids and we'd just been talking about the milkweed aphids on another thread I had aphids on the brain! LOL I'm pretty sure the milkweed aphids are aphids although I could be wrong.
pbyrley Wake Forest, NC (Zone 7b) November 10, 2008 10:01 PM	ecrane3, I don't know how to put 2 pictures on one post so I did the adult milkweed bug. I believe that orange things that look just like aphids are the larvae of the milkweed bug. I think they fill the void because milkweed would kill regular aphids. Whether I'm correct or not, I don't think it's a good idea to smash them with a bare hand. I may try the insecticidal soap on them this year as my milkweed plants are still small. In previous years (when I lived in a different place), the orange bugs/aphids didn't seem to harm the milkweed and the monarchs had a successful molt. I don't mind sharing the milkweed with 2 insects as long as monarchs get theirs ok. Paul
ecrane3 Dublin, CA (Zone 9a) November 10, 2008 10:51 PM	Trust me, I would never in a million years squish a bug of any sort with my bare hands! LOL

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