I've a LOT of palms, mainly 'Christmas palms' and have just noticed an infestation of long thin worm like larvae that live down the centre of each frond leaving brown spots all along each frond until they go black and die. I'd tried the usual pesticide (foul smelling stuff in small brown bottles, no, not Lao Khao ), which didn't have any effect, so pulled the buggers off by hand (took hours ). Anyone have same problem and how to get rid once and for all? I've Googled, but to no avail. Thanks.

Possible coconut hispid (or hispine) beetle (Brontispa longissimi) a long slender beetle with long slender larvae, both adults and larvae feed superficially on the leaf and petiole tissues and cause stipling and frond disfigurement at the least, and sever dieback and mortality at the worst. Look at Google images to identify. Or post photos.

For non food palms you could use a systemic insecticide as a soil drench, for root uptake and translocation throughout foliar crown. When the pest feeds it injests the insecticide. Starkle G is dinotefuran is a fast uptake systemic with about a 3 month residual effectiveness; Imidacloprid (Ive seen it sold in Thailand farm chemical shops as a Bayer product, Imidacloprid 10%) is a more common systemic, it has a slower uptake but up to a year residual.

For food or oil palms, it is not appropriate to use a systemic, so you could spray a contact insecticide like Chaindrite Stedfast (cypermethrin) or other pyrethroid like permethrin or alphacypermethrin. Follow label directions. Repeat applications once a month.

On organic product may not be effective for an advanced infestation, but preventively you could spray a botanical product like neem or pyrethrins, but it would take weekly or every two weeks treatments because of short term residual effectiveness.

If it is in fact the hispid beetle, there is a biological control. There was a project through the Thai Agricutlure Dept biological control division, a natural parasitic mini-wasp that was released in Samui and some other areas to suppress the devastating infestation for the coconut industry. It is difficult to obtain this biological control agent for release.