I was extrapolating from the flea treatment, since I've heard him talk about both. But the original flea treatment is a little different (though I still think you ought to give the nematodes a try), because I do think there is a soil-level stage for ticks. Yes, they climb trees and shrubs, but when they've finished a blood meal they don't hop back on a bush, they drop to the ground. I think that's where you'll get them.

From the Dirt Doctor site about tick treatment:

Treatment is the same as the flea control explained on the web site with one change. Ticks like to camp out up high and be ready to jump off on passing animals for a little blood meal. Spray the shrubs, tree trunks, sides of buildings, etc. with one of the fire ant drench mixtures containing compost tea, molasses and orange oil.

Beneficial Nematodes

Beneficial nematodes should be used for soil-borne pests. Overall broadcasting is best. Spot treating helps if the budget dictates. In an organic program one treatment a year is usually enough. No, they do not hurt the beneficials. Apply per the label instructions for the control of fleas, ticks, grubworms, termites, fire ants and roaches. Beneficial nematodes are just one of the beneficial microbes that exist in healthy soil. That's why they seem to control more pests than they are supposed to.

Root knot nematodes: Many nematodes are beneficial, but there are those that will attack ornamental trees, garden plants, and lawn grass. Controls include increasing the organic matter level in the soil, using organic fertilizers, and applying products that increase microbial activity. Cedar flakes applied to the soil surface will also help. You can also use a citrus oil drench or citrus peeling pulp tilled into the soil prior to planting or used around existing plants.