BOGOTA (Reuters) - Colombia must maintain eradication and substitution of coca crops as a long-term policy across the Andean nation s isolated jungle and mountain zones to permanently defeat drug trafficking and consolidate peace, the defense minister told Reuters. A new government, which will be elected next year, must keep up the policy if the nation hopes to stamp out the illegal drugs industry, which has funded Colombia s half century war that has killed more than 220,000 and displaced millions.  There can be no interruption to this policy because there s a new government, not in 2018, nor in 2022 or 2026,  Defense Minister Luis Carlos Villegas, 60, said in an interview.   It has to be a process of at least a generation so that it bears fruit and that there s true peace.     Since signing a peace accord last year with the Revolutionary Armed Forces of Colombia (FARC), the government has focused efforts on clearing coca from areas once controlled by the rebels.  Coca, the raw material that makes cocaine, is cultivated in about 188,000 hectares across Colombia by subsistence farmers who have few other opportunities to feed their families.  Criminal gangs, right-wing paramilitaries and Marxist rebels form the purchasing chain that has helped make Colombia one of the biggest producers of cocaine.  Cocaine seizures reached 300 tons so far this year and may exceed the record 362 tons seized last year, said the minister, who formed part of the government s peace negotiating team with the FARC. As part of the policy, the government plans to invest in development programs - building schools, health centers and roads - to allow poor farmers to improve their social conditions and sell legal crops like cacao, fruits, coffee and palm oil. Colombia s vast rural expanse lacks roadways, so Villegas said infrastructure that brings communities closer to market are vital for eradication to work.  It s not enough to plant cacao to replace coca ... thousands of miles of tertiary roads are needed,  he said. Colombia wants to manually eradicate 100,000 hectares of coca this year, with farmers voluntarily destroying half of it. The United States has raised concerns about the increase in coca production and cultivation, which has reached levels seen a decade ago, arguing that the increase is a result of Colombia s ban on aerial fumigation. Despite pressure to resume spraying, using glyphosate, a chemical linked to cancer, Villegas ruled out the possibility.  It s off the radar,  he said. 