The standard avocado medication for phytophora (root rot) is phosphorus. I have chosen to treat my two stricken trees with phosphorous (phosguard or agri-fos) by trunk injection. As many people have learned...this is a great treatment with good results. It is not a cure. Google this. If you can't figure this treatment out...post again for me and I will help further.

I see a few problems: the spotted leaves are either a persa mite or fungus no a problem but the infected leaves will fall off. you should white wash the entire tree or move it to a shaded area until it starts to recover. how long have you had it were the brown tips there when you bought it? what have you fertilized with? i give even my new trees food. for small trees like yours if watering twice a week where i am its not super hot, i use a liquid b vitamin once a week for first month and make sure the ph of your water is below 7 i treat them like my blueberries and they love it more nutrient uptake. 5.5 - 6.5 is best. there are several ways to lower ph of water. twice a month i water with a dilution of ammonia sulfate which is 21-0-0 (2 tbs to 5 gal bucket of water.) that will push new growth. and once a quarter i add a little organic slow release avocado food, azomite. and i use a flower fert 2-10-10 before bloom time for heavy flowers... i have multiple trees in pots that are 10-15 ft tall and 8 ft wide heavely fruited. so you have to be on a good feeding schedule.

Tom, I'm just making some assumptions here but this is my take: lots of these chainsaw-happy folks are new homeowners (or new to suburbia) and unfamiliar with either landscaping or gardening at all and are not, as you say, tree-savvy. And they have read or been told all those horror stories about large trees on their property - they will fall and destroy the house (not necessarily true), their roots will invade and damage the foundation (also not necessarily true and far less common a situation than one would imagine) and you can't grow anything under them or even in close proximity (again, not necessarily true). They consider this and determine the only viable course of action is removal. Out come the chainsaws!! Of course, the more reasonable alternative is that after purchasing a new home, they have visions for the landscape/garden that don't include a heavy population of trees. But that doesn't exactly jive completely with the wholesale removal of anything on their property that grows taller than 10'. I think some folks are just plain scared of large trees. Period. If that's the case, do not move to the more suburban or rural areas of the PNW - big trees (and I mean BIG) are extremely common in virtually any garden. And depending on area, removal during the construction phase is done only by permit, is closely monitored and in some cases, removal of any existing native trees must be followed up with a suitable replacement.

Thank you for all of the feedback! I have had two certified arborists take a look at the tree, and both said they thought it was Armillaria fungus. I sent some pictures into an agriculture lab at Purdue and they did not 100% confirm it was Armillaria, but they thought it might be as well. I will indeed start to complete some more research on this. The arborist yesterday was tapping the affected root, nearby roots, and the trunk and we heard a number of "hollow" sounding areas. The canopy seems very thin (although I have only lived here for a couple of months, so maybe it has been that way for awhile). I have noticed two branches (2-4 feet in length) fall off the tree since we noticed the rot. The leaves on them looked okay, however I found a handful of small sticks with brown/dry leaves attached in our yard yesterday. It seems like there is definitely some issues with the tree at the top. Trust me, I don't want to take this tree down if I don't have to! It adds so much to the house and would be very costly to remove. I appreciate everyone's comments and will keep digging. Troy