By Mikejforde
Victoria,
Australia 
New gardener here - we have a young dwarf lemon tree in a pot which has adapted very well to its new home - it has already flowered this year.
Today I noticed these stick-like things attached to some of the leaves (see pic)
What are they? Are they harmful? How do/should I remove them?
20 Nov, 2016
Answers
Grey Twisted Moth Caterpillar....Circopetes obtusata. I think that's it. :)
20 Nov, 2016
Yes that looks like it!! Thank you!
I will spray with white oil tomorrow and hope they didn't get all the flowers / baby lemons!
20 Nov, 2016
Well thanks for putting it on Mike...I found it quite fascinating! :) good luck!
20 Nov, 2016
More of a leaf eater, but it can reduce the crop by reducing the leaf area. I would use B.t. or spinosad, myself, if only because oil sprays are so hazardous in my hot climate. I had a similar species eating a bonsai Ginkgo at work. I had a hard time figuring out what was chewing on it, until I suddenly noticed a "twig" that wasn't there before! Quick work with the fingers, and the Ginkgo had its revenge. :)
20 Nov, 2016
Welcome to GOY. I would just pick them off and drop them into neat bleach. I keep some handy for disposing of slugs and snails.
20 Nov, 2016
ooooh..how fascinating! Looking at the chewed edges of the leaf, I think we have a caterpillar here, disguised as a bit of twig. Great disguise isn't it! Better get them off I should think! Sorry, I don't know the name of the offending bug. :) but someone will.
20 Nov, 2016