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I have a rose. I have noticed that some of the leaves have got white dots and do not look healthy. There are also strings between some of them (similar to spider webs). I also noticed some small flies around my rose a few weeks ago.

Can someone explain what is going on and what I should do? What can I do to avoid a similar situation in the future?

Here are some pictures:

Click any image for full size

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Update:

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The white spots seem to be inside the leaves. The leaf on top is washed with warm water and there are still the white spots.

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There are moving black creatures under the leaves. There are also things that look like eggs/larvae.

Update 2:

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2 Answers 2

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I can't tell from the photos whether the white on the leaves in the penultimate picure is a deposit on the leaf, or within the leaf tissue itself. In the last picture, it looks more as if dust or dirt has stuck to the leaf. If its a white, powdery deposit on the leaf, and it's not dust or dirt, its got mildew. As for the insect infestation, aphids love roses, and sometimes look like white dots on the foliage, but with webbing, not sure what other beasties you may commonly have where you live. Suggest you check the underside of the leaves and leaf joints for signs of aphids, larvae or eggs. Spider mite infestation springs to mind - this would also cause white mottling of the leaves, but I'm not sure whether that's an outdoor pest in your area or not.

I'd like to ask a few cultural questions, but instead, I'll dish out the cultural advice. Roses are high maintenance - they need spraying every fortnight from spring through to fall with a systemic fungicide/insecticide. They need feeding with a specialist rose food at least twice a year (usually spring and 6 weeks later, if a granular formulation) to supply everything they require on the nutrient front, in particular to enable them to fight off infection/infestation better. They prefer heavier soils, with plenty of sun, and need good pruning to aid airflow between the branches to reduce the risk of fungal infection.

Without a description of the flies you saw, they could have been anything from hoverflies to rose sawfly, hard to say. If you suspect spider mite, spray with an appropriate insecticide. That will take care of any aphids present too. If there's mildew present, you can try finding a combined fungicide/insecticide treatment which will cover all the bases, or you will need to spray with a fungicide separately. Or try the milk treatment (1 part milk, 9 parts water) sprayed till run off on top and beneath the leaves and on the stems.

UPDATE: Seen all the pics - that just looks like a fly, not a hoverfly or sawfly. If you were in the UK, I'd recommend Roseclear Ultra or Roseclear 3 combined systemic insectide/fungicide, but I've no idea what products are available in Toronto for this kind of thing. Guess you could check whether the product is available there - otherwise its a case of reading the boxes/bottles on products to see which one/s you need. Roses aren't particularly susceptible to damage from pesticide sprays, but always remember to spray after the sun has gone down, but obviously before its dark, when the bees and other pollinating insects have stopped working, and avoid spraying open flowers.

I think you've got a problem with leafhoppers and spider mite, so if you can't find a combined fungicide/insecticide, just get an insecticide and use that, preferably a systemic one that mentions those two pests on the list of things it treats. How often you need to use a Systemic insecticide varies depending on formulation, but the instructions should be on the bottle or box. Contact insecticide will only kill off what's currently present in terms of insects, and won't prevent repopulation, so you may find yourself having to use it very frequently.

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There are moving small black creatures under the leaves and also stuff that look like eggs/larvae. I will add new pictures shortly. –  Kaveh Sep 6 '12 at 18:39
    
The insects were very small (a little bit larger than the size of the head of a pen) and completely black. Can you suggest some fungicide/insecticide? I am wary of harming the plant by using an inappropriate one. –  Kaveh Sep 6 '12 at 18:48
    
ps: thanks for advice, I live in Toronto, Canada and I got this rose for a few months, and I like it very much and don't mind spending time to take care of it. –  Kaveh Sep 6 '12 at 18:52
    
I uploaded two pictures of the flies I mentioned. –  Kaveh Sep 6 '12 at 19:00
    
It seems (from Googling) that Roseclear is probably not available here. I will check the available products as you suggested, thank you. –  Kaveh Sep 6 '12 at 21:24

Looks like whitefly to me. A couple of sprays of white oil mixed with water or even garlic infused water should do it. Spray the concoction all over the leaves, including underside.

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I don't they are whiteflies, they are not white. –  Kaveh Sep 25 '12 at 18:04

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