I planted this Brogdon Avocado from a three gallon planter about 3 weeks ago. It has developed a white powdery substance at the lower end of the main stem. Can you help me identify this and let me know how to treat it. From the research I've done it looks like either white powdery mildew or Avocado Dothiorella Canker but neither of the description fit it 100%. The leaves don't seem to be affected and I don't see any canker or lesions on the stem under the white powder. It also seems to have a light touch of it reaching up the stem about half way up the tree. I have watered twice fairly heavy since it has been in the ground but I don't think I have overwatered. The tree looks healthy otherwise (so I think) but I'm new to this. Any help would be appreciated. http://i287.photobucket.com/albums/ll155/butchew/Avocado%20Tree/garden04-08-2008051.jpg

http://i287.photobucket.com/albums/ll155/butchew/Avocado%20Tree/garden04-08-2008052.jpg

http://i287.photobucket.com/albums/ll155/butchew/Avocado%20Tree/garden04-08-2008064.jpg