Wasp hoped to save cassava crop

Photo by: Photo Supplied
Mealybugs (top) have already destroyed cassava crops in Thailand, but experts hope that the release of the Apoanagyrus lopezi wasp will reduce their impact in Cambodia.

via Khmer NZ News Media

Tuesday, 29 June 2010 15:03 Christy Choi and Thet Sambath

Paraguayan insect already saved Africa from mealybug disaster, expert says

THE government has approved the importation of a Paraguayan insect parasite that farmers in the northwest hope will combat a pesticide-resistant mealybug infestation that is threatening cassava crops, officials said this week.

Hean Vanhan, the deputy director of the Agriculture Directorate at the Ministry of Agriculture, Forestry and Fisheries, said the parasite – named Apoanagyrus lopezi – was expected to arrive in early July, but that the insects would be bred in a controlled environment before their release. “The imports should arrive next week, and breeding should take 10 weeks,” Hean Vanhan said.

The Post reported in March that cassava mealybugs – small, white pests that destroy cassava – had been detected in multiple districts in Banteay Meanchey province. In Thailand, the presence of mealybugs is one factor expected to reduce cassava yields for 2009-10 to 23 million tonnes, down from an earlier projection of 29 million tonnes. The Bangkok Post reported in February that private-sector analysts had predicted that the yield could drop to as low as 20 million tonnes, a decline that could translate into the loss of hundreds of millions of dollars.

According to the 2009-10 annual report from the Agriculture Ministry, released in April, there are approximately 160,000 hectares of farmland devoted to cassava in Cambodia, and around 3.5 million tonnes of cassava are produced each year.

Rod Lefroy, regional coordinator for the International Centre for Tropical Agriculture, estimated on Monday that the Cambodian cassava industry is worth US$300 million annually.

The Cambodian War Amputees Rehabilitation Society, which works with cassava farmers in the northwest, asked the government for permission to import Apoanagyrus lopezi on April 2, said John Macgregor, the NGO’s communications director.

He said the mealybugs posed a direct threat to the livelihoods of 3,000 cassava growers working with the NGO in Battambang province, and could potentially affect thousands of others in Battambang and elsewhere.

Unless they are controlled, Macgregor said, the mealybugs could result in the same type of damage that hit a group of 30 African countries that became infested with mealybugs in the 1980s.

“The 30 African countries that were hit by mealybug in the 1980s saw an average 80 percent destruction of their crops, some 100 percent. The same potential exists here,” he said.

He added, though, that Apoanagyrus lopezi had provided a successful solution.

“A lopezi was subsequently released in 30 countries across Africa, where it terminated a continent-wide mealybug infestation. This saved the African cassava industry from destruction, and prevented millions of people from starving to death – all while not harming anything else,” he said. “It was the most successful biological control intervention ever.”

Officials at the Agriculture Ministry could not provide statistics detailing how many hectares of Cambodian farmland have been affected by mealybugs so far, nor could officials at the Agriculture Department in Battambang. An official at the Agriculture Department in Banteay Meanchey, who spoke on the condition of anonymity because he was not authorised to discuss the issue with a reporter, said 8,382 hectares of crops in that province had been affected.

Macgregor said the stocks of Apoanagyrus lopezi due to arrive next week are being provided by Thai entomologist Amporn Winothai, who could not be reached for comment on Monday.

Lefroy described the release of the parasite as “imminent”, but noted that it would need to be approved by the Thai government.

“Cambodia will not be able to release the parasites until the Thai government approves the release in Thailand – in other words, when exports are approved,” Lefroy said.

Officials at the Thai Ministry of Agriculture and Cooperatives could not be reached for comment on Monday.

Macgregor said the onset of rains has curbed the spread of the mealybugs, but that officials are expecting the threat to surge again towards the end of the wet season in late October.

Hean Vanhan at the Agriculture Ministry said that even if the importation of the pests had not been approved, they would likely have migrated into Cambodia after being released in Thailand’s mealybug-affected areas.

“They will be in Cambodia soon anyways. It’s part of the natural movement. No one can stop them,” he said.