Help! What is this pest?

liveinaboxMay 13, 2014

Novice gardener here who has inherited a well-stocked garden! At the back of my garden is a rhododendron which ispretty big and has white flowers (only been here a few months so I've never seen it flower, although the estate agents pics show it flowering last summer!). There have been dozens of flower buds on it for a good 4-6 weeks now but not one has opened.
I've noticed that the leaves are covered in black 'soot', but as we're next to a busy road I put it down to road dirt (although it doesn't affect any of my other plants). Today upon closer inspection I've noticed hundreds of little creatures on the stalks of the shrub (nothing on the leaves or the flowers). They are squidgy and slug-like, not hard like a beetle. They are flatter than a slug and are less than 5mm long.

Can anyone help me identify what these are and how to get rid of them? I have pets and a toddler so preferably nothing too toxic, although I can keep them away if that's what's required. It's a big bush and it's infested so I'd rather not have to scrape them all off by hand!

Sorry that's so long, thanks in advance!

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rhizo_1 (North AL) zone 7

Look up aphids and compare with what you have. If not aphids, it would be helpful if you could post a picture.

If they are aphids, you could try strong sprays of water in order to dislodge the pests. Done every few days, this method can be very effective. Occasional applications of insecticidal soap can be helpful, too.

Try to direct the spray on to the aphids, it works by direct contact to the pest. Best to use commercial soap sprays as home made concoctions can cause damage to the leaves and are not as effective as the real stuff. There are many brands.....be sure to read the label and don't get one with other added pesticides.

    Bookmark   May 13, 2014 at 9:46AM
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liveinabox

Ok I think I've attached a photo! They're not aphids (I have those on my roses!), they're more 'slimy' than that!

    Bookmark   May 13, 2014 at 2:47PM
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Dave in NoVA • 7a • Northern VA

Sure looks like a type of scale to me. Hopefully others know the best remedy. Perhaps a horticultural grade of oil sprayed in evening?

    Bookmark   May 13, 2014 at 3:44PM
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akamainegrower

Your description sounds like some sort of pyslla. I've never heard of this as a pest on rhododendrons, but I can't think of any reason why it couldn't be, either. Could the "soot' and the creatures be two different things? If you can, I'd take a leaf or two to a good local nursery or the UK equivalent of the agriculture department for identification before doing anything.

    Bookmark   May 14, 2014 at 5:54AM
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mikebotann(8a SE of Seattle)

What type of tree is growing above the rhododendrons? Aphid droppings could be the source of the soot mold that you think is road grime.
I've never had that type of bug on my rhododendrons so I can't offer any solution for them. A systemic insecticide used for roses might be useful. It's sprinkled on the ground and watered in. The plants absorb it and the bugs eating your plants die. Personally, that would be my last choice if all others fail.
Mike

    Bookmark   May 18, 2014 at 10:29AM
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dlcooper52a(NC Mtns, z7)

Mike's surely right that you are seeing mold encouraged by excrement of the scale critters. Aphids cause the same malady. But his reluctance to use a granular systemic is questionable. It takes quite a while to work (water it in immediately) but is much more effective than any contact spray, and may spell the difference in life and death of the plant, especially on armored scale, a toughy. So quick action is necessary.

For limited outbreaks scale can be removed by scraping, but that is tedious. Better to wipe them out thoroughly.

The (Bayer?) granular "rose" product is a generic systemic insecticide and is the easiest to find. There is also a liquid systemic that can be sprayed on plants, from Ortho, but Rhodo leaves may not quickly absorb it.

Good luck!

    Bookmark   June 5, 2014 at 1:49PM
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