Yes ticks are gross and Yorkies are built low to the ground. Check w/ your County Extension office (just google your county and the largest city your near to and the words extension office. Their website should have a number to the Master Gardener office) check with them to see if there are any deer ticks also because they carry lyme disease and you and your dog can be effected if you are bitten. And check with them to see what they recommend to treat your yard with. They usually know what is effective and how to apply. When I am in Maine I have always kept my guy in a short cut. If we walk by the edge of wooded areas he occasionally picks up a few. I check him (and myself) daily because I am a gardening fool…
there is a product I use on my gardening pants and boots because I am in an area where there are many deer ticks and Lyme Disease is prevalent it is called Pyrethrins and basically comes from the Chrysanthumum. It is toxic to cats but not can be applied to humans and to dogs but you have to be aware of the do's and don'ts and toxicity levels. Here is a great article about it by an Emergency Vet Tech
http://davesgarden.com/guides/articles/view/3892/#b I find Pyrethin effective against ticks…however I never did put it on my dog. But many say it is very effective. Why don't I because by the time I discovered it the dog had positive titers for Lyme as many many dogs do in areas with deer tick. I assume you are dealing with mostly dog ticks. They are disgusting and they are gross but they don't carry Lyme. There are ticks that carry different diseases your county extension office will know and they are a wealth of knowledge and free (the only thing they sell are usually gardening books and publications) so they will give you non-biased advice which your local state university agriculture/science program has determined valid for your area. I know this is long winded but I hope this helps you and your pup.