Oh, ick

This creepy little bugger is phyllocnistis citrella, the citrus leafminer. I say creepy because they kind of remind one of parasitic worms, maybe the kind that would tunnel under your skin? It's not a worm, but the larvae, or caterpillar if you will, of an ugly little moth. Yes it seems I may have found the ugly insect, and it's having its way with my sweet little kumquat tree. Remember it was all flush with new growth after I finally remembered to water it? The tree is now covered with silvery, curling leaves where the miners have chomped tunnels through the palisade cells, leaving the shiny epidermis and frass.

Anyway, the recommended course of action is to "encourage natural parasites", consisting of several wasps that parasitize the citrus peel miner (not to be confused with the citrus leafminer, except of course by the parasites we hope!), as well as a wasp that will be imported from p. citrella's native home. Apparently the pest originated in Asia, arrived in CA in 2000, and worked its way to Orange County where it is now rampant. More info can be found here and here. Local nurseries are suggesting the use of sprays containing spinosad, a derivative of fermented bacteria (Mmmmmm) that supposedly will not harm beneficials since they would not be likely to ingest it. I'm going to test its effectiveness. A question that nags me: If the miner must ingest the spinosad, and the miner is inside the leaf (under the cuticle), yet the spray is applied to the leaves which are covered and protected by their cuticle, how is it the larvae come into contact with the spinosad? More on this in a few days.

I would have to say the spraying seemed to have some effect (ie I noticed a few larvae that seemed dried up/dead) but did not positively control the infestation. I cut off some of the worst leaves, for aesthetics but more importantly to prevent the larvae from becoming breeding adults. On a larger tree, this pruning might be a good way to go, coupled with spraying with spinosad EARLY in the infestation period.