They may be restricted on the kind and amount of chemicals that they can use on the course. At my dad's course, they have an infestation of a larvae each year that makes a mess of the fairways. They also have a mosquito problem. In both cases, they aren't allowed to treat the problem because of environmental concerns. In the same vein, I saw an interview with the president of the USGA and he was saying that they are encouraging North American courses to severely limit the chemicals and WATER they use on courses and to let the land go back more toward its natural state, much like they do in the UK.