COYUCA DE CATALAN, Mexico (Reuters) - The Mexican army says its fight against surging opium production that feeds U.S demand is increasingly complicated by the rise of smaller gangs disputing wild, ungoverned lands planted with ever-stronger poppy strains.

The gangs have engulfed the state of Guerrero in a war to control poppy fields, turning inaccessible mountain valleys of endemic poverty and famous beach resorts into Mexico’s bloodiest spots.

Colonel Isaac Aaron Jesus Garcia, who runs a base in one of the state’s most unruly cities, Ciudad Altamirano, told Reuters on an operation to chop down poppies high in the Guerrero mountains that violence increased two years ago when a third gang, Los Viagra, began a grab for territory.

Bodies are discovered almost daily across the state, tossed by roads, some buried in mass graves. In Ciudad Altamirano, the mayor was killed last year and a journalist gunned down in March at a car wash.

“These fractures (in the gangs) started two years ago, and that caused this violence that is all about monopolizing the production of the drug,” Jesus Garcia said.

From this frontline of the fight against heroin, Jesus Garcia sees a direct link between a record U.S. heroin epidemic that killed nearly 13,000 people in 2015 and violence on his patch.

“The increase of consumers for this type of drug in the United States has been exponential and the collateral effect is seen here,” Jesus Garcia said.

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Heroin use in the United States has risen five-fold in the past decade and addiction has more than tripled, with the biggest jumps among whites and men with low incomes.

Jesus Garcia said the task of seeking out poppy fields in one of Mexico’s poorest and least accessible regions, rising above the beach resorts of Acapulco and Ixtapa, was practically endless.

His 34th Battalion and others send platoons of troops on foot for month-long expeditions every season. They set up camps and fan through treacherous terrain, part of a campaign that destroys tens of thousands of fields a year.

One such field visited by Reuters was deep in a lawless region six hours from Ciudad Altamirano through winding dirt roads thick with dust that rose into the mountains.

It was irrigated by a lawn sprinkler mounted on a pole that spritzed water over less than a hectare of poppies and fertilizer bags were piled nearby, basic farming techniques the soldiers nevertheless said were a sign of growers’ new sophistication.

A dozen troops fanned out, chopping down the flowers with machetes.

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HIGHER YIELDS

Army officials said gangs use poppy varieties that produce higher yields and more potent opium from smaller plots, and that its higher value is driving violent competition between gangs.

“Now we see more production of poppy in less terrain, and it has to do with the quantity of bulbs each plant has,” said Lieutenant Colonel Jose Urzua as he showed bulbs oozing valuable gum from slits. He explained opium is often harvested by families.

In these tiny mountain hamlets opium has grown for decades, officials said, but a coffee plague and the U.S. opiate epidemic has led farmers to plant much more.

The harvest has become central to Guerrero’s economy, also dependent on cash sent home by immigrants.

One army official said the field seen by Reuters could produce around 3 kilos (6.6 lb) of opium, fetching up to $950 per kilo from traffickers who sell it for up to $8,000.

“There aren’t many alternatives here,” said a woman selling soft drinks and snacks from a pine shack by a dirt road. Her husband grows poppies, and she said anyone who runs a business faces extortion by gangs.