I moved into a house several years ago that had a major flea infestation. I live out in the country but my yard is fenced. I have four dogs that stay covered in fleas. Frontline doesn’t touch this problem. I buy permethrin at Tractor Supply to dip them in. I spray the yard with any and everything. Its better but still really bad. I need Industrial strength bad stuff to kill these things. I don’t care if it kills the grass just not all the trees. Its heavily shaded which makes it worse. Sulphur helps but I would really like a remedy. Any suggestions?