Notes: One of the most frequent questions that gets asked regarding the issue of herbicide resistant weeds is "How long does resistance last in absence of further selection pressure?". Some studies have shown that resistant biotypes can continue to dominant a weed population for at least 7 years after selection pressure is reduced. Thus, limiting the use of a particular herbicide or family of herbicides is not enough in itself to help minimize problems with resistant weeds. Additional control strategies will be required. Another good reason why the response to herbicide resistant weed problems should be pro-active rather than reactive!