On June 22, 1999, about 1945 hours Hawaiian standard time, an Enstrom F28C, N595H, sustained substantial damage when it collided with trees during departure from a ranch at Kaunakakai, on the island of Molokai, Hawaii. The commercial pilot/ owner and passenger both sustained minor injuries. They were departing on a local personal flight and operating under the provisions of 14 CFR Part 91. Visual meteorological conditions prevailed and no flight plan was filed. The pilot stated the helicopter was running well and there was no mechanical failure. He estimated winds were variable from 040 to 080 degrees, and gusting from 25 to 35 knots. He entered hovering flight prior to departure and determined all systems were working, but noted it was after dusk. He stated that during the transition for departure he encountered a dust devil; blowing dust and debris filled the cockpit. Dirt got in his eyes, obscuring his vision as his eyes watered, and the helicopter collided with the trees as he tried to put it down. The pilot declined to complete a pilot/operator report. Federal Aviation Administration records indicated the pilot's total time was 2,500 hours.