A goat perhaps? I know around here they do the job pretty well, we had some bad fires and now there is a "preventive firefighting team" which involves a bunch of goats that are 'let loose' in areas where the brush has become so dried and overgrown it is a fire danger. They do a really good job: here is an article.
http://www.10news.com/news/9524584/detail.html
I know you can buy them through groups like this:
http://donate.wvus.org/OA_HTML/xxwvi...4&item=1352788
$75. for one or $150. for two, might be more cost-effective than using toxic chemicals in the long run.
A considerable discount than the $200. price on Tower, even with tower discounts.