We are surrounded by commercial orchards. These trees are either pulled up by the roots or grafted. These are not organic orchards. Can I use these for making hugelculture beds?

Absolutely.  Wood is wood.

Wood from commercial orchard fruit trees will be a hard wood (unlike pine or other soft wood coniferous trees).  It will break down much slower, which is a good thing in the long run.

Two hesitations:

1.  The wood will most likely have been sprayed with all manner of 'cides—insecticides, fungicides, and perhaps even herbicides.  If you are hard-core organic, you may not want to be transporting those chemicals onto your operation because they will hang around for a few years.  However, if you bury the wood and give it two years to decompose, the bacterial and fungal herd will tie-up most of those chemicals and render them inert.

2.  Why did the trees die?  You don't want to be importing fungal diseases like apple scab, brown rot, peach leaf curl, perennial canker, crown gall  . . . or any other nasty disease, that now is likely to be fungicide resistant.  I would be careful about dragging that wood through my existing orchard, leaving a trail of fungal spores in my wake.  If the trees have died of some sort of root rot, you might want to think twice before you create a carbon rich bed that will be a fungal nursery for these little hitch-hikers.

That said, I regularly import thousands of pounds of wood chips and spread them throughout my orchard/food-forest.  I've never had so much as peach leaf curl. 

Thanks, Marco. There's so many commercial orchards around here that ppl can't grow their own fruit trees organically. That rules out apples, pears, and summer fruits. Because of this, a lot of our plants attract pollinators.

Do you know if any of the diseases you mentioned would affect nut trees?

I don't now too much about nut trees.  We have one almond tree --- that's the full extent of my nut orchard, and it's only been in the ground for 8 months.  I don' t have much personal knowledge about nut crops.

The more I thought about your situation, I'm inclined to think that using that wood should be OK.  If the trees died and were subject to the weather, the sun would irradiate most of anything bad, the rain, snow and cold would take care of most everything else.  In nature, the forest doesn't carefully quarantine every fallen tree that dies of a weird disease.  It falls, rots, and feeds the soil.

If you've got access to cheap fruit all summer, then I would imagine that your hugals are for gardening/annuals.  Use the fruit tree wood.  Bury it a bit deeper and let the good fungi do it's magic.  If at all concerned, bury it and wait 2 years.  It'll take that long to start to break down and give you the full benefits of a hugelculture.

On a personal note, we have great friends who live just north of you up in Kelowna BC., so I'm a bit familiar with your climate.  My wife was born in eastern WA and raised in Tacoma ---- our old stomping grounds.  I'm curious about your soil.  Rocky? 

One hill is rocky, another sandy, but you never know if you'll hit a rock...or when. It's even more fun when you plant a veggie garden. One seed is in sand, the next clay.
We're "snuggled up to the Cascades", so we get less rain than most of Eastern WA.

I grow a lot of what we eat on a south-facing hillside that is quite steep.  What is nice about south-facing hills is that they extend your growing season significantly.  For every 5 degrees of slope, it's like moving your land 100 to 150 miles south.  So a 25 degree hillside is like living 500+ miles further to the south.  That slope absorbs heat, and gives you a larger growing surface, more sunlight, etc.  It will heat up sooner in the spring and maintain soil warmth longer into the fall.

While I don't do hugels on a hillside, I pile organic material on the down-hill side of my fruit trees.  On our hillside, I've got 2 avocados, 3 figs, 5 asian pears, 4 peach, 2 cherry and 2 nectarines.  Below each of these trees is a berm of branches, leaves, pumpkin/tomato/gourd/cucumber/sweet potato vines . . . just tons and tons of carbon from yard waste, garden waste, tree branches, wood chips, etc.  Over the years, those brush piles have slowly rotted down and created amazing soil beneath. 

Why the down-hill (south) side?  Because the uphill side is shaded by the tree, but the downhill side absorbes the full brunt of the hot summer sun.  The trees have benefited tremendously, but I also plant other stuff around them and everything does better as a result.  Vining plants cover the piles during the summer—I'll have to reach up onto the top of the pile to pick a watermelon.  In the heat of the summer, the sun hits those piles, not the earth below, keeping the soil cooler and saving soil moisture.  During the winter, the piles are a great habitat for lizards (my snail and slug patrol).  With each passing year, the soil below the trees continues to get richer and darker.

So . . . if you are gardening on a slope and are creating an integrated food forest, that might be one option.  Particularly if your slope is south facing.  It's a whole lot easier to pile stuff up and leave it to slowly rot, than it is to build hugals.  After a while, those brush piles act as a like of terrace, capturing falling leaves and other organic material.  They look somewhat like a nest below each tree.  Some of them are tall enough that I can stand of them when I pick fruit --- another added bonus. 

I don't know if you have dug swales, but that is a long-term step that is actually regenerative in building soil, as organic material collects and breaks-down in the swales.  If you have a swale, pile your organic material in the swale (where it will break down faster) or on the uphill side, where it will keep the soil moist and wash down as it decomposes.  It sounds like drainage wouldn't be a problem on your sandy/rocky land, so a swale might be a nice place to collect a bit of water after larger storms, but then infiltrate it and moisten your carbon/composting plant material in the bottom of the swale.  In a couple of years, you should have a couple of inches of good soil in which to grow your plants.