Prevention of fig tree suckers

My neighbor has two Desert King fig trees that are about 45 years old. They are about 15” diameter at the trunk. When I started managing his trees for him about 20 years ago, they were already quite tall and very difficult to harvest due to height, so I topped them at about 15’ high. In general that has worked well because it has resulted in a huge Breda crop which is the only crop that ripens here near Seattle. However, I have been faced with the annual task of trimming off the multitudes of suckers that come up around each tree. I had a similar problem with my own fig tree which I have solved by placing an impenetrable barrier around the tree that goes out about a foot from the tree base. But my efforts to prevent my neighbors trees from suckering have failed. My feeling is that my neighbors tree has been filled aground the based by soil after it was planted since when he tills his adjacent garden soil, the excess spills downslope to his fif trees. That may explain why his trees sucker so profusely.
So I am asking if anyone has found a good way to discourage or prevent fig tree suckers without use of chemicals? If so please advise.
Kent, Wa

Figs like to take a bushier shape and will naturally throw a lot of suckers. I do not know of any way to prevent this. I just rub out unwanted nodes as they start to form. Any that escape are a source of cuttings for future trades.