Thai farmers aid spread of parasitic wasp

19 July, 2010 by (comments)

Thai cassava farmers came prepared for the official release of a swarm of parasitic wasps, which it is hoped will help the country tackle a devastating cassava mealybug epidemic. Some of them brought containers to collect their own samples of the tiny Anagyrus lopezi wasps.

Around 400 farmers attended the release ceremony in northeastern Thailand on Saturday (July 18th), organised and hosted by the Thai government’s Department of Agriculture.
Wasp release

By releasing the wasps in their own cassava fields, the farmers will contribute to the planned dissemination of A. lopezi to all the country’s cassava fields by the end of they year.

Click to see the official press release and Friday’s announcement on the CIAT blog for more information about the combined efforts of the Thai Department of Agriculture, TTDI, CIAT and IITA to bring the mealybug problem under control.

CIAT’s regional research coordinator Rod Lefroy attended the release ceremony and sent these pictures, and the following report.


Wasps launched into cassava fields amid festival atmosphere

by Rod Lefroy in Thailand

After months of work by the Thai government’s Department of Agriculture (DOA) and the cassava industry’s Thai Tapioca Development Institute (TTDI) to rear large numbers of a minute wasp, Anagyrus lopezi, a ceremony was held on Saturday 17 July to release the wasp so it can start the work of controlling the menacing cassava mealybug.

The ceremony was held at the DoA’s Khon Kaen Field Crops Research Center in the heart of NE Thailand, where some of Thailand’s more than 400,000 cassava farmers are located. The event was hosted by the Director General of DOA, Mr Somchai Charnnarongkul, and officiated by HE Mr Supachai Phosu, the Deputy Minister of the Ministry of Agriculture and Co-operatives.

The Director of the center in Khon Kaen, Dr Peaingpen Sarawat and her staff prepared a festival atmosphere for the release, which included speeches, exhibitions, and finally the release of the wasps. As the wasps are so small, before releasing them from plastic vials directly onto cassava plants, there was a symbolic release of helium-filled orange balloons, many of them carrying paper cutouts of a magnified wasp. The balloons were released simultaneously by Mr Supachai, Mr Somchai, and Mr Adul Vinaiphat, Vice President of TTDI. As the balloons floated high above the cassava fields the guests of honour and many others released an estimated 10,000 wasps.

A small number of breeding pairs of the wasps arrived from Benin, West Africa, in November 2009; then the hard work of mass rearing them started in Thailand. Under the expert eye of Dr Amporn Winotai, the DOA entomologists charged with responding to the mealybug outbreak, her team established two mass rearing facilities at the TTDI site in Korat and a DoA site in Rayong.

Wasp release2

Tests were carried out to ensure that the wasp would control the mealybug and not become a predator or parasite of other insects. Once the tests were confirmed, permission was granted by the Director General of DOA for the release of the wasp, by which time it was estimated that at least a quarter of a million wasps had been reared.

The occasion also marked the extension of responsibility for rearing the wasp and controlling the mealybug to include the Department of Agricultural Extension (DOAE), whose Director General took part in the release ceremony. DOAE and DOA staff from all the cassava growing areas will be trained and equipped to rear and release the wasp, with the aim of reaching all of the more than 1 million hectares grown to cassava in Thailand by December this year.

Of the participants in the ceremony, there were more than 400 cassava farmers. Many farmers had worried that the problem of mealybug infestation that occurred last year, resulting in an estimated drop in national production of 20 to 25%, and much higher declines on individual farms. Rather than change to other crops, they stayed with cassava, which is very well suited to local conditions. They followed the current recommendations to select clean planting material and, where necessary and possible, to dip the stakes in a systemic insecticide prior to planting, to give the plants a better chance to establish without having to fight the mealybug.

On Saturday, the farmers were very happy to witness and be part of the release of the wasps and to have another important weapon of control, especially as it is expected that mealybug numbers will increase after the rainy season draws to a close in October.

In an effort to be in the frontline of the war against the mealybugs, many farmers were seen collecting the wasps in small containers immediately after the release to take back to their own fields and thus start the gradual expansion of the wasps across all of Thailand’s cassava fields.

CIAT scientists, particularly entomologist Dr Tony Bellotti, who discovered the biological control possibility of Anagyrus lopezi, and Dr Tin Maung Aye, the CIAT’s cassava agronomist based in Bangkok, played critical roles in helping Thailand identify the mealybug species and access and raise the wasp, while CGIAR sister center the International Institute of Tropical Agriculture (IITA) in Benin provided the initial breeding population of 500 pairs wasps.

With the release of the wasps and the prospect of Thailand’s mealybug problem being brought under control, the end of the first battle against pest and disease problems for cassava in SE Asia is now hopefully in sight.

Now, the focus needs to shift to controlling the cassava mealybug in neighbouring countries, where the problem spread, or will soon appear. At the same time, monitoring for other emerging pests and diseases is needed, together with the development of good short, medium, and long term responses to these new threats to cassava production in SE Asia.


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