You might want to put your zone into your profile so we can better help you, and put a photo of the problem here. It's hard to help without seeing the problem. Also post this in the California forum. Lots of avocado growers there.

Take photo of the avocado or install surveillance camera to see who eat or pluck the avocado. Growing avocado in Singapore

Hi everybody, Thanks very much for all of the feedback - much appreciated. Here's the follow-up: I was agreeing with the fungus theory (and the overfertilized theory), and then I took two leaves from this plant to my local garden center where I got a chance to show them to our local plant expert (sells houseplants and does a regular column in the newspaper). He looked at the leaves carefully and said that not only does this plant have scale but it has *spider mites* and he believes this is the crux of the problem. He diagnosed the spider mites by a slightly metallic sheen the leaves had when held up to the light. Also, there was a fair amount of honeydew on the leaves, which I thought was a product of the scale. He sold me some Bayer's Rose and Plant Insect Spray which I have dutifully sprayed all over the plant. I confess I'm feeling pretty guilty about this since I generally prefer organic means to work through things like this but the plant is in such distress I caved in and bought the spray. I'm going to give it a week and see what happens. I also intend, once it's had a few days to recover from the spraying, to replace all of the potting soil and thus eliminate the overfertilization variable. Thanks again for all of your suggestions. If any of you thinks that this solution seems mistaken, please feel free to respond. cheers, papercarver

Seeds are only started in water by people who don't realize how easy it is to plant them directly into a good potting mix! I'm wagering that your plant is dying. You may want to try again with a new pit. Allow one to ripen inside the avocado until the fruit is very soft. At that point the seed may already have started to crack. Wash and dry the seed, and nestle it in, pointed side up, in a very coarse textured potting mix, leaving the 'nose' exposed. Water thoroughly, place in a warm, well lit location,and water when the medium dries somewhat.