Ticks on horses?

Is there anything we can use to keep ticks out of our horses ears (they are on pasture 24/7 and are not always closed in, so need something that lasts more than a day or 2), and is there anything that can be put in their ears that will kill the ticks but not harm the horses.  We moved to texas 4 years ago, so this is a new thing for us.  We did not have any problems until this summer.  I am going to have to locate an equine vet that makes farm calls as the guys will not let me remove the ticks. Our rescue horse will not let me touch his ears.  We just noted this problem today, so was hoping you might be able to assist. 

Our very popular Bug Check will more than help…
You will just need to give a few scoops daily rather than 1/2 scoop which is typical maintenance. It should greatly help. Topically, I would use our Bug Check spray… it is not 100% natural, but it is as natural as we could get it and still have a killing effect on the ticks. Topical ointment would be our Marigold healer.