Its two-stroke engine spins a metal blade, which is more commonly deployed to tame the suburban gardens of wealthy Westerners. But today, in a remote valley in impoverished Shan State, Myanmar police armed with weed-whackers are advancing through fields of thigh-high poppies, leaving a carpet of stems in their wake.

When the police are finished, their uniforms are flecked with a sticky brown sap harvested from these flowers for centuries: opium. Myanmar produced an estimated 610 tonnes in 2011, making it the world's second-biggest opium supplier after Afghanistan, according to the United Nations Office on Drugs and Crime (UNODC). The area under poppy cultivation has doubled in the past five years.

Now, emerging from half a century of military dictatorship, Myanmar says it wants to buck that trend.

Since taking power a year ago, the nominally civilian government of President Thein Sein has launched a series of political and economic reforms. It has also dramatically accelerated a campaign to eradicate opium poppies and shed Myanmar's pariah status as one of the world's top drug producers.

Myanmar officials allowed a Reuters reporter and photographer to visit former conflict areas in remote Shan State to examine the campaign, marking the first time in decades that Western journalists were able to report freely in the region.

The five-day journey with the UNODC and local police came as Myanmar appeals to foreign donors for half a billion dollars to finance a program it says will wean 256,000 households off poppy-growing over the next three years.

WIPED OUT BY 2014?

"Every year the international community spends millions of dollars (on anti-narcotics initiatives) in countries like Afghanistan and Colombia, and the outcome is not satisfactory," Sit Aye, senior legal advisor to President Thein Sein, said in an interview. "Here, with international assistance, we guarantee to wipe out the opium problem by 2014."

It is an ambitious goal. Police, soldiers and villagers armed with sticks and weed-whackers have destroyed 21,256 hectares (52,525 acres) of poppy fields since September, more than triple the area eradicated during the previous growing season, according to Myanmar's Central Committee for Drug Abuse Control (CCDAC). This has potentially prevented almost 30 tonnes of heroin, opium's most notorious derivative, from hitting the world market, according to calculations based on UNODC statistics.

But opium had been harvested from some poppies before they were destroyed, Reuters found. And while more poppy is being destroyed, more is also being grown: the total area under cultivation will likely rise by about 10 percent between 2011 and 2012, the UNODC estimated. This suggests that, with or without foreign assistance, Myanmar's three-year target is unrealistic.

Most opium produced in Myanmar comes from Shan State, a rugged and lawless region bordering China, Thailand and Laos. It is part of the Golden Triangle, which is probably named after the gold once used to buy opium. Here, and in neighbouring Kachin State, poppies thrive not just on cooler weather and higher altitudes, but on poverty and conflict.

For half a century, Myanmar has been torn apart by fighting between government forces and various ethnic rebel groups ranged along its borders, where people have endured the worst human rights abuses.

The United States recently upgraded diplomatic ties with the long-isolated Southeast Asian nation after Hillary Clinton's historic visit there in November, the first by an American secretary of state since 1955. But the U.S. and European countries regard Myanmar's making peace with its long-suffering ethnic minorities as a key condition for lifting crippling economic sanctions.

Forging a lasting peace is arguably Thein Sein's toughest challenge, and it is complicated by opium. As in Afghanistan and Colombia, the drug trade has long fuelled conflict in Myanmar, providing cash to buy weapons and a lucrative product to fight over. Opium and conflict were so intertwined that one problem could not be solved without the other, said Jason Eligh, UNODC country manager for Myanmar.

"The path to peace is lined with poppies," he said. "We must address that."

Recent peace talks between the government and ethnic rebel groups -- including two factions of the Shan State Army -- have allowed poppy eradication in what were once no-go areas for the Myanmar authorities. But the ceasefires were fragile, and a poorly managed eradication campaign could cause them to unravel.

ALTERNATIVE CROPS

Chopping down opium poppies is the easy part. Helping former poppy-growing families develop alternative crops and livelihoods is complicated and costly.

In Afghanistan, on the other side of the Himalayas, opium production is so vast and sophisticated that it resembles a legitimate agribusiness in some areas. But in Myanmar, poppies are produced mainly by subsistence farmers who depend upon the cash opium generates to buy food.

About 256,000 households are involved in opium poppy cultivation, the UNODC estimates. The opium yield from an acre (a third of a hectare) of Myanmar poppy is worth about $1,000. That's a life-saving sum of money in Myanmar, where a third of its 60 million people live on a dollar a day.

"The rapid elimination of opium poppy creates serious problems for these households," Eligh said. "You have people who couldn't harvest their poppies, who don't have any money, having to survive for the next five or six months with almost nothing."

Alternative crops can't be planted until the rains come in June or July. "We've got a very narrow window," Eligh continued. "If they don't get help during that period, then there is a very real chance that they'll go back to poppy."

The UNODC argues that the ceasefires create a rare opportunity for the international community to help Myanmar tackle its opium problem -- and, by extension, its civil war. The CCDAC is asking the international community for $524.48 million to develop alternative livelihoods for poppy-growing households.

Getting it will be an uphill task. Thanks to sanctions, Myanmar receives less humanitarian aid per capita than almost any other poor country.

"After 1988 we were sanctioned and banned by Western countries," said Police Colonel Tin Maung Maung, the most senior operational officer in the CCDAC. "We got no assistance from them." Without outside help, he said, "We cannot do it. We need international support."

BLESSING AND CURSE

Myanmar's strategic location is a blessing and a curse. As it emerges from nearly 50 years of isolation and misrule, the country's long borders with China, India and Thailand grant access to Asia's most dynamic economies. They also make it a regional hub for manufacturing and distributing narcotics.

It shares a porous 2,100-km frontier with China, where 2.2 million users consumed 45 tonnes of mostly Myanmar heroin in 2008, said the UNODC.

Shan State is named after Myanmar's largest ethnic minority. The road east from its capital, the former British colonial hill-station of Taunggyi, is a ribbon of blacktop unfurling through rice fields and bustling market towns. At the roadside, Buddhist novice monks in maroon robes held out bowls to solicit donations. This reporter travelled in UN vehicles sandwiched between trucks carrying armed police. Their presence was not ceremonial.

Last July, outside the nearby town of Loilem, a rebel group called the Shan State Army (South) ambushed a Myanmar police convoy, killing six people, reported the Shan Herald Agency for News, a news service run by Shan exiles in Thailand. Shan rebels and a government militia belonging to the Pa-O, the state's second-largest ethnic group, clashed regularly.

Hostilities subsided in December after the SSA (S) signed a ceasefire, but men with guns still roam this restive region. UNODC regional chief Gary Lewis described Shan State as "a swirling and often toxic mix of money, guns and drugs."

CHEROOTS, TEMPLES AND GARLIC

The Pa-O are devout Buddhists, known for growing poppies and building beautiful temples. At the village of Kyauk Ka Char, the first stop in the five-day tour of the state, the temple was the grandest structure in a community of simple wooden houses with rusting tin roofs.

Inside, three giant Buddha statues smiled down upon a group of villagers waiting to greet their rare visitors: Lewis and Eligh from the UNODC, and Police Colonel Myint Aung of the CCDAC. The villagers wore turbans, in the Pa-O style, and smoked cheroots and chewed betel nut.

Lewis delivered a stark message. "The days of poppy are finished," he told the villagers, before asking what help they needed to grow only legal crops.

Nobody said a word until a local schoolteacher, who was translating between Pa-O and English, urged people to talk freely without fear of arrest. The authorities had destroyed their poppies once before, in 2005, and given them no compensation or assistance.

Growing alternative crops wasn't easy, said Aung Tun, 40, a father of four. Many people grew cordia trees, whose leaves were used to make traditional Myanmar cheroots. But the recent influx of cheap Chinese cigarettes meant that fewer people smoked cheroots, making the leaves increasingly unprofitable.

"We tried growing garlic and sugar cane but there was no market for it," Aung Tun said. "We lost everything we invested." Garlic fetched such a low price that some Pa-O villages left it to rot in the fields.

Transporting these crops to market was also a problem. Poppy-growing villages such as Kyauk Ka Char are remote, with unpaved roads only passable in the dry season. By contrast, the market for opium was guaranteed and transport wasn't an issue.

Most farmers grew two crops. The first, which accounted for three quarters of the annual opium yield, was planted in September or October, and harvested about three months later; then a second crop was planted. Areas with good irrigation could even plant a third.

During harvest season Chinese-speaking traders on motorbikes toured the villages and paid cash for opium. "You don't even have to take the crop to market," said Eligh. "The market comes to you."

POPPY DEBTS

Moe Mohm, 48, a single mother of six daughters, had borrowed 300,000 kyat from a Taunggyi moneylender to buy fertiliser for her poppies, which were recently destroyed. "I just wanted to cry," she said.

With her cash crop gone, Moe Mohm couldn't repay the loan or even the interest on it -- a crushing 8 percent per month. She had no way to grow rice until the rains came, and no cash to buy it. "We know your need is great and more help is required," Lewis told her. "We will act on it."

On the way back to Taunggyi, Eligh called a colleague at the World Food Programme and an emergency supply of rice arrived in Kyauk Ka Char less than three weeks later. More rice was bound for other villages nearby.

The UNODC has three projects aimed at current and former poppy-growers in Myanmar. Located in the Shan townships of Hopong and Loilen, the projects offered a range of assistance: developing alternative crops, improving the land with irrigation and fertilisers, providing microfinance to landless households, setting up cash-for-work programmes, vaccinating livestock, and building roads and clinics.

This is funded with $7 million from the European Union, Germany and Japan. It was "barely enough" to help 10,000 of the 256,000 households involved in opium poppy production, Eligh said.

When the poppy fields of War Taw, a village in Loilen township, were destroyed, the UNODC gave people tools, seeds and agricultural training. But this help was not enough to stop War Taw's young men and women from leaving for Thailand, where an estimated 2 million Myanmar people now work, most of them illegally.

With the poppies gone, that exodus could accelerate. Nang Khae, a 49-year-old poppy-grower, reckoned about 60 villagers -- a tenth of War Taw's population -- worked in Thailand. Her 29-year-old daughter left for Bangkok five years ago to work as a maid and never returned. Three months ago, her teenage son left too.

"It breaks our heart to watch them go," said Nang Khae. "But we had to borrow money to buy food and can't pay it back. That's why we send our children away."

TRADITIONAL MEDICINE

Poppy eradication removes not just a cash crop but, for many hill-tribes, a medicine. The villagers of Kaw Mong Pyin, an isolated village in Eastern Shan State populated by ethnic Akha, regard opium as a life-saving traditional remedy. "We've used it since our ancestors' time," said Asan, 43, a poppy-grower who was raising 10 children and 20 oxen.

Asan's village felt untouched by modernity. The women wore elaborate headdresses hung with coloured beads and silver coins dating back to British colonial times. Pigs slumbered beneath wooden houses with thatched roofs.

When his cattle got sick, said Asan, he fed them a mixture of ginger, garlic, salt and opium. The villagers also baked opium with garlic to treat their own diarrhoea, a life-threatening illness in remote areas. Without opium, he said, the villagers would need basic medical help for their families -- the nearest hospital was a five-hour walk away. "We only use a little," said Asan. "Too much makes you dizzy."

But another pressing health issue is opium addiction, which is rife among hill-tribes such as the Akha. "Every time I go home I start smoking again," said Abo, 49, a long-time opium smoker being treated at a government clinic in the Shan town of Kengtung. "No poppies are grown in my village, but opium is very easy to buy."

POPPY PROLIFERATION

The weed-whackers destroy not just fully grown poppy plants, but also a hard-to-spot second stage of seedlings which some farmers plant between them. "This year's opium crop will be greatly reduced because of these tools," said Police Colonel Win Naing, Shan State's chief of police.

UNODC officials agreed, but cautioned that eradication wasn't the only factor influencing the season's total production.

One was bad weather. In many parts of Shan State, heavy rain had washed away poppy seeds or damaged young plants. This alone might have halved the yield before eradication began.

Another factor was the total area under cultivation, which had risen by at least 10 percent between 2011 and 2012, estimated the UNODC. In other words, although more poppies had been destroyed, more had also been planted.

A third factor became apparent outside Kyauk Ka Char, where a poppy field the size of a soccer pitch lay strewn with stems. These were felled in a recent operation but, as tell-tale marks on their bulbs revealed, not before some of the opium was harvested.

This suggested that the ongoing eradication campaign might not reduce the total yield by as much as the Myanmar authorities had hoped.

The poppy-farmers of Kyauk Ka Char might have received a tip-off. More likely, the police had simply arrived too late. Since 2006, China's National Narcotics Control Commission has given Myanmar satellite maps to help locate and destroy poppy fields. But Shan State police said they have gotten no other international assistance, and were hampered by lack of personnel and equipment.

Many fields were so remote and well-hidden that not even satellite maps were much help. "Sometimes, we have a map but still can't find the field," said Sai Aung Kyaw Win, 39, a veteran UNODC surveyor who spends months trekking through Myanmar's poppy-growing areas. "We just walk around in circles."

INTERNATIONAL ACCEPTANCE

Neighbouring Thailand was proof that alternative development worked, the UN's Eligh said, although it took more than 30 years and a billion dollars to halt large-scale poppy-growing there. Thailand still produces about 5 tonnes of opium every year, despite dispatching troops on regular poppy-eradication missions. This fact alone suggests that Myanmar's bid to eradicate opium in just three years is fanciful.

But the target of 2014 was chosen for a reason: that year, for the first time, Myanmar will mark its growing acceptance by the international community by chairing the Association of Southeast Nations (ASEAN), a position it was denied six years ago amid Western uproar over its human rights record.

One potentially embarrassing UNODC survey map showed dense poppy cultivation only a few hours' drive from Myanmar's capital Naypyitaw, where ASEAN and world leaders will gather in 2014.

ASEAN has declared that its 10 member states will be "drug free" by 2015, an equally fanciful target considering the region's soaring use of methamphetamine.

Better known in its pill form as ya ba, it is also manufactured in huge quantities in Shan State. When asked whether poppies or pills were the bigger law-enforcement challenge, Pol Col Tin Maung Maung of the CCDAC replied, "Both are a great problem for us."

(Editing by Bill Tarrant)

• A Permanent Economic Emergency