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I recently noticed what looks like small beetles on our dwarf citrus tree. Can anyone identify this abnormality?

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Is this something harmful that I should attempt to treat?

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See also this question about scale. –  bstpierre Jun 16 '12 at 22:41

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That looks like the worst case of scale I've ever seen. Are the tops of the leaves sticky, and is there more of it on the central rib of each leaf (top and/or bottom)? If so, that pretty much clinches it.

Yes, you definitely need to treat it. You'll find some advice here, but maybe someone has better advice for such a horrible infestation. What I would do is start by wiping it all off with small cloths soaked in rubbing alcohol. When you've gotten rid of all the adults (the brown bumps in the picture) there will still be lots of eggs and larvae. Spray the plant with neem oil or similar to get rid of the kids.

Scale-poo can be hard to clean up from underneath the plant, depending on what it's on.

Make sure this isn't near any other plants that you care about! Frankly, I'm tempted to recommend discarding the plant. Keep an eye on anything that has been nearby - it will "jump" from plant to plant.

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That's what I was afraid of. I've never seen scale this...LARGE. What I'd seen previously looked like water spots on a potted plant. –  Randolph Jun 16 '12 at 23:50
    
If you do plan on saving it, it may take at least a few years to eradicate the scale. I THINK we've finally got rid of it on our citrus (which we bring in each winter), but I've used a systemic and discarded the fruit for a couple of years too. –  thursdaysgeek Jun 19 '12 at 22:02
    
@thursdaysgeek Yeah, the only thing that got rid of it all, for good, for us was systemic as well. I didn't want to suggest it for citrus, though. –  Ed Staub Jun 19 '12 at 23:39

Scale for sure. Manual removal means wiping them off. Use a wet soapy cloth and rubber gloves as they will become a mushy slime. You might consider purchasing Lady bugs to do some of the work, especially their larvae. Adults will breed and the babies will be extra hungry. Water the foliage before releasing the ladybugs so they can have a drink after their long voyage. Weekly applications of a safer soap or horticultural oil may also help.

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The problem with ladybugs is that they may not feel any need to stick around and eat your bugs when the wide open sky is available –  kevinsky Jun 18 '12 at 22:16
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I agree. Though if watered and they sense a good food supply for their eggs, you can be sure that they will deposit the eggs near a good food source. True, the adults will fly away in a matter of a few days but what they leave behind is what you want. –  BlueStar Jun 18 '12 at 22:25

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