Crevice in petiole

[David_Sweden]

On my ~5 feet high Rhopalostylis baueri, one of the fronds has always been a bit paler (more yellow) ever since I got it almost a year ago. And on that frond's petiole there is a crevice which I thought is the reason for that. It is about 1" long and 1/10" wide, placed about a foot from the base. It reaches into the center of the petiole, and if I poke a thin steel wire gently into it, I can reach about 2" upwards and 1" downwards.

The first image shows the crevice, the 2nd the pale frond, the 3rd the whole palm (and the 4th is just a picture of the "saxophone style root" which shoots out roots even from its top now).

I poked the hole once a year ago and was relieved when it wasn't deeper, thinking it might be some insect (borer or larva).

The last weeks the paler frond has become paler, and some brown streaks and cracks in some leaves too. I discovered two weeks ago it is under attack by root mealybugs, which I have a plan for threating, and I though that (in addition to it just last week getting a long needed repotting, and not being leached for almost 6 months until 3 weeks ago, and the winter with dry air even though I make some efforts to add humidity) was the reason it was a bit tired, and that it shows almost only on that frond because of the crevice making it weaker, and that it hopefully should grow out of it now. New fronds come at a good rate still (5 months apart in the winter, a bit more often in the summer). Artificial light gives 0,5-4 klx on most leaves, and it is close to a NNW window with morning sun. It is the 2nd oldest frond, to the left in the full sized picture.

But now I'm wondering if it after all might be some borer or larva that is in there? Does anyone know what that looks like? Any reason to be worried? Shouldn't it/they either come out or make a mess when I poke it?

Edited April 18, 2015 by David_Sweden