* Labour shortages expected to hit main harvest season
* Cassava prices in Monrovia rose by 150 pct in August
* FAO needs $20 million for response plan (Adds TV tag, details of FAO response)
By Isla Binnie and Emma Farge
ROME/DAKAR, Sept 2 (Reuters) - The world's worst Ebola epidemic has endangered harvests and sent food prices soaring in West Africa, the U.N. Food and Agriculture Organisation (FAO) said on Tuesday, warning the problem would intensify in coming months.
The FAO issued a special alert for Liberia, Sierra Leone and Guinea, the three countries most affected by the outbreak, which has killed at least 1,550 people since the virus was detected in the remote jungles of southeastern Guinea in March.
Restrictions on people's movements and the establishment of quarantine zones to contain the spread of the hemorrhagic fever have led to panic buying, food shortages and price hikes in countries ill-prepared to absorb the shock.
"In the three countries severely affected by Ebola, the agriculture and food security situation is really deteriorating," said Vincent Martin, head of an FAO unit in Dakar that is coordinating the agency's response.
"People either cannot afford to buy food or it is not accessible anymore," he said in an interview, adding that the food crisis could hinder containment of the disease, which is typically spread via the bodily fluids of the sick.
Rice and maize production will be scaled back during the fast-approaching main harvest season as migration and movement restrictions cause labour shortages on farms, the FAO said.
Cash crops like palm oil, cocoa and rubber will be seriously affected, squeezing the purchasing power of many families, who will also lose income and nutrition due to the ban on bush meat.
The price of cassava at a market in the Liberian capital Monrovia rose 150 percent in the first weeks of August, the FAO said, adding that currency depreciation in Sierra Leone and Liberia was likely to force prices up further.
Border crossing closures and the reduction of trade through seaports have tightened food supplies in the three countries, which are all net cereal importers, and propelled prices upwards, exacerbated by higher transport costs.
The U.N. World Food Programme and the FAO have approved an emergency programme to deliver 65,000 tonnes of food to 1.3 million people affected by Ebola over a three-month period.
Food is to be shipped to Ebola patients, suspected cases living in isolation and to communities within the badly-affected border zone of Guinea, Liberia and Sierra Leone that has been surrounded by a "cordon sanitaire" to prevent the further spread of the disease.
In a sign of the lack of provisions within treatment centres, a man escaped from an Ebola treatment centre in Monrovia this week and walked through a market in search of food.
"Sometimes you have an area right next to a quarantined area where there is food but you can't get it there," Martin said.
Liberia, where cases are increasing fastest, said in August that it has only enough rice stocks to last for about a month.
The WFP says it needs to raise $70 million to pay for its emergency programme. In addition to this sum, the FAO is seeking to raise $20 million to help isolated populations grow their own crops and support themselves, Martin said.
"Delivering food directly to the population is not sufficient. What the FAO is proposing is to see how we can help restore their livelihoods and help them cope by providing tools to produce good and nutritious food," he said, and raising chickens or short-cycle crops could form part of the solution. (Editing by Mark Heinrich)