I remember reading neem oil is not tolerated well by japanese maples

I have had that happen to a couple of my seedlings, although I never figured out what was causing it. I am nearly convinced that trunk rot was the likely case for this problem, as there was no evidence of any pests and the seedlings had been planted about 2 inches too deep. I have since repotted the surviving plants (and new ones) being sure that the root flare is at soil level.

Last winter/spring just prior to leafing out I also found some type of caterpillar that destroyed some limbs on my small 'aconitifolium'. The little beast chewed rings around the young twigs killing the twigs.

I would suggest thouroughly checking the soil to be sure that the pest is not living there. I would most likely put some type of non constrictive tape around the base, although I'm not sure that this is the best course of action.

My advice would be to inspect the roots also for evidence of damage. It sounds like there may be root weivels present. These are a beetle larve, approx 1/4" long. If these seedlings are potted individually inspect for the larve by sifting through the soil. I have no treatment advice that has been 100% sucessful. Nematodes seem to be effective, once the trees are girdled they are done for.

Definatly root weivels. I had this problem a couple years ago on some new stock purchased for grafting. Couldn't save them. Here is a good link with info.
http://www.pfc.forestry.ca/diseases/nursery/pests/rootweev_e.html

Grancru

Thanks everyone for the info. I know I have adult weevils in my yard as my rhodies always have notches in the leaves. It sounds like there isn't much I can do to kill the larvae. Tomorrow I will dump out the soil in the pots and see if I can find the little buggers. The trees need to be put in bigger pots anyway. Thanks again. Karen