Weaver ants more effective than insecticides in protecting orchards

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Weaver ants more effective than insecticides in protecting orchards

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weaver ants

Weaver ants

Insecticides are inferior to weaver ants when it comes to protecting orchards. Attendees at a recent workshop in Africa were told that using the ants in mango and cachew orchards was not only cheaper than insecticides, they were more effective, acted pre-emptively to control pests and had no residual effect on the fruit. Dr Renkang Peng attended the starting workshop of the research project ‘Increasing value of African mango and cashew production’ in Benin, Africa between 9th and 19th August 2011. This project is coordinated by Aarhus University, Denmark in collaboration with six research organizations in four countries (Benin, Tanzania, Demark and Australia). The project is funded by the Ministry of Foreign Affairs of Denmark for a period of four years (2011 – 2014). Charles Darwin University (CDU) Australia was invited to participate in this project because the weaver ant technology developed at CDU will be used for all the field experiments in Tanzania and Benin. The technology developed at CDU involves managing the ants at the colony level so that the ant populations remain high and stable. The major threats to weaver ant populations include fights between colonies, and the effects of competition with other ant species.

 participant practice
Workshop participants practise the weaver ant technology under Dr Peng’s supervision

However, the CDU research team has developed management techniques to minimise these risks. As long as the ant populations are healthy, the ants themselves do the rest of the work. They are voracious predators, and their prey includes almost all of the insect pests of tropical tree crops. They constantly patrol the trees and either capture or chase away the pests. Because the ants are constantly at work, they do a better job at controlling the pests than farmers can do with insecticides. By the time even the most diligent farmers spot the pests, the damage has already been done, but the ants keep the pests from ever becoming established in the orchards. Apart from being as effective (or even more effective) than insecticides, using the weaver ants as biological control agents has several other economical and environmental benefits because the insecticides are expensive and they have residual effects on the fruit, in the soil, in the watershed, and on other fauna in the orchard. The African project will concentrate on the development of integrated pest management programs (IPM) for mango and cashew growers in both Tanzania and Benin. The project aims to improve crop yield and quality, and includes four parallel working programs:

  • The development of IPM programs for cashew and mango crops,
  • An ecological study of the local weaver ants,
  • The establishment of weaver ant nurseries, and
  • The development of market links for organic cashew and mango produce.

Each working program has one PhD student or a post-doc, and a total of 20 people (6 PhD students, 2 post-docs and 12 supervisors) are involved in this project. The major role of CDU in this project will be:

  • to help the project leader supervise programs 1, 2 and 3, and
  • to write a photo book based on African local conditions of cashew and mango production and the results that will be obtained from all 4 programs for agricultural extension officers, farmer field school trainers and cashew and mango growers in Africa.

In this first workshop, Dr Peng overviewed the development and implementation of IPM programs using weaver ants as a key element to increase value of cashew, mango and forest trees in Australia, Vietnam and Thailand.

He worked closely with project participants in the field to teach them about the bio-ecology of weaver ants and how to properly use the weaver ant technology that has been developed at CDU. All the participants were very interested in the two photo books and a manual written by Renkang Peng and Keith Christian for cashew and mango growers and extension officers in Australia and Vietnam, and they said that they considered these documents to be the most important references for this African project.

The workshop participants expressed their appreciation of having Dr Peng’s expertise as part of the African project. In the next 4 years, Peng will spend a part of his time on the African project, including annual trips to Africa to supervise the project on site, collect data through field surveys and take photos for the manuals and photo books he will produce.