That's scale. Mealy bugs are white, wooly critters.

That's one of the many soft scale insects. Your homework assignment is to type -mealybug images- into Google. ;-)

Spinosad isn't particularly effective for scale insects and I would not apply a pesticide that won't work. I don't think that Spinosad is even recommended for the control of pests in the insect order Hemiptera. But are you aware that it is a very broad spectrum pesticide....and should be used with the utmost caution for fear of killing beneficial species.

Horticultural oils are the first resort when trying to control these pests. Call your local Extension office to find out which oil they recommend for scale and when to apply it.

I strongly urge you to familiarize yourself with scale insects, especially the soft brown scale. If you have so many on one young fruit, I worry about what the rest of the tree might look like....including the stems.

I previously posted a branch of this tree, and the insect was ID here as mealy bugs. The close up tells it all!

I thought scale was white! I did my homework assignment. You are right! The infected area seems confined to one main stem, and we'll investigate the best horticultural oil for this tree. The good news is this tree is one that must have grown from a seed and the lemons are no bigger than a quarter and full of seeds. We hope to graft other citrus on it in the future.

I know to spray spinosad at night so it doesn't hurt the bees. We definitely need that for leaf miners, of which we have tons, and on other trees and plants with various insects.

Thanks for the advice!

Suzi