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Some white spots appeared recently on my Twilight chilli plant (indoors), on some leaves brown spots start appearing in the middle. First I thought - aphids, but it doesn't quite look like insects. Or those very small insects. The white thing can mostly be found on the upper surface of leaves. It is a bit sand-like in touch.

the white thing on the upper surface the white thing on the lower surface the brown and the transparent spots

The transparent spots on some leaves (visible on the last photo) had appeared earlier, but I didn't panic about those, as the plant seemed otherwise healthy. In fact it still looks quite healthy apart from the described symptoms – it is flowering and first fruits grow.

I am afraid about my other plants on my windowsill – three other chillies and a tomato. They do not seem affected now, though.

What is it? Can it be powdery mildew or rather those are some insects? How can I fight it?

Do all the symptoms (white 'sand', brown spots, transparent spots) seem related or, maybe, some of them can be just an effect on some bad care from my side?

Update 2012-05-15: Thanks for the comments. You may be right, these are scale insects. Though, today I was able to take a bit better pictures and it doesn't quite look like on the other question:

affected leave white 'sand' brown spots

I am starting a treatment, with soap, vinegar and scissors, like it is scale, anyway.

Update 2012-05-22: Just after my last update I have started my 'treatment'. I have washed the leaves and whole plant with a soap and vinegar mixture, then flushed with clear water. I was able to get rid of most of the white stuff and for a moment things looked well. But in an hour first leaves started wilting. In a couple more hours most of them wilted. The next day most of the leaves and some branches were clearly dead. The pests would probably not harm this plant as I did… I hope they were killed together with the most of this plant.

Probably the solution was too strong, the leaves to delicate for such treatment or I was not able to flush it properly. Or all of these. Do not try this at home!

Out of curiosity I have kept the plant to see if it can survive. Now, a week later, new leaves and branches appear. The three fruits are still there, even some flower buds seem still alive. The pests are nowhere to be seen, but I know I need to wait a few more weeks to know if they are really gone.

The next time the bugs appear, I will buy some pesticides at a local gardening shop and use them properly rather than trying a compilation of 'organic' treatments described on the Internet. :)

Update 2012-06-19: Over a month passed and the plant recovered from my 'treatment'. Unfortunately so did the insects. Yesterday I have found them on my Cayenne plant, then one adult on a Habanero and lots of small ones on the Twilight, which started this story. This time I have bought a pesticide (systemic, for chewing and sucking insects) in a nearby gardening shop and sprayed all my plants… I hope this time the results will be much better.

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What you have does not look like powdery mildew, looks (from here) more like a scale. If so, see this question. –  bstpierre May 14 '12 at 17:35
    
@bstpierre Yes, it seems so. It was hard to look it up until someone said what to look for. Consider adding this as an answer, so I could eventually accept it. –  Jacek Konieczny May 14 '12 at 18:20
    
I'm voting to close as a dupe. I definitely agree that it's hard to figure out what kind of thing you're looking at until someone suggests a word for it. –  bstpierre May 14 '12 at 18:33
1  
@bstpierre - It seems very unlikely that someone searching for a problem on vegetables would stop to look at a search result titled "What is this palm tree disease...". Also, the photos are quite different - in fact, I wouldn't have recognized this as scale except for the two mature bugs in the bottom photo. So I wouldn't close this a dupe. –  Ed Staub May 14 '12 at 19:39
    
Whatever else you do - get this away from the rest of your plants quick, and check them carefully! FWIW, I never had any luck with organics for scale - we had it on a house-plant, and were finally, reluctantly able to cure it with systemic granules - NOT to be used for vegetables. –  Ed Staub May 14 '12 at 19:43
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1 Answer 1

up vote 5 down vote accepted

The last picture clinches it - it's undoubtedly scale.

Scale is really hard to get rid of entirely. For most of the lifecycle it's very tiny and impossible to spot all of. It spreads to other plants. It leaves a sticky residue underneath the plant that's hard to remove. So... consider tossing the plant.

You can slow it down a lot with organic sprays, and by peeling the brown adults off with a thumbnail if it won't damage the plant. After you think it's gone, keep treating the plant and inspecting daily for a couple of months. The life cycle of scale is about 6 weeks, and for most of it's life it's virtually invisible.

Keep infected plants away from other plants. No flying is involved - when young they crawl.

Another technique is to spray or gently wipe down the leaves (tops and bottoms, being sure to get around the bottom central rib) with rubbing alcohol.

For any given technique, you can find five people who say it doesn't work, and one person that says it does. Regardless of what you use, you must continue long beyond when you think it's gone.

The sticky honeydew they leave on the leaves often grows sooty mold, a black fungus - rinse or gently wipe it off occasionally.

Definitely NOT my favorite critter!

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Neem oil works very well for me. Spray them down! –  Grady Player Jun 20 '12 at 14:14
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