BOISE, Idaho (AP) — U.S. officials are testing a new wildfire retardant after two decades of buying millions of gallons annually from one supplier, but watchdogs say the expensive strategy is overly fixated on aerial attacks at the expense of hiring more fire-line digging ground crews. The Forest Service says tests started last summer are continuing this summer with a magnesium-chloride-based retardant from Fortress. Fortress contends its retardants are effective and better for the environment than products offered by Perimeter Solutions. That company says its ammonium-phosphate-based retardants are superior. The Forest Service used more than 50 million gallons of retardant for the first time in 2020 as increasingly destructive wildfires plague the West.