Correct identification of pest prevents mango crop destruction and saves millions

Correct identification of pest prevents mango crop destruction and saves millions

Problem Statement: In 1981-1982, a new insect was found to be seriously damaging mango, citrus and other fruit trees in Ghana and Togo, and soon spread to the rest of West Africa. The loss at this time to the mango and avocado export industries in Ghana alone was estimated as at least £130,000/year.

Methods: Samples sent to a taxonomist were compared with material in collections, and, although the mealybugs of southern Asia are not well documented, the taxonomist was familiar with the fauna and was able to recognise the pest and its area of origin immediately. The pest was identified as an undescribed species of mealybug from the genus Rastrococcus native to southern Asia. Consequently the search for natural enemies was targeted on India and Malaysia.

Outcomes and Impacts: The species was quickly recognised as an Asian species new to science and was named Rastrococcus invadens. A undescribed hymenopteran parasitoid (since described as Gyranusoidea tebygi Noyes) was found in India and, after screening, was introduced to Togo in early 1987. It spread rapidly and has provided good ongoing control of the pest. Effective control in Africa was achieved within 18 months of location of a parasitoid, thus preventing potentially significant crop and economic losses. Socio-economic surveys indicate that the savings from in Benin alone have amounted to US$ 531 mil over 20 years, with a cost / benefit ratio of 1:145.

Lessons: This example illustrates how quickly biological control can be established if timely, authoritative taxonomic input is available. It also highlighted the poor knowledge of the Asian mealybug fauna, which could result in similarly damaging introductions in the future. Subsequently the genus Rastrococcus was thoroughly researched and revised. A large monograph on the mealybugs of southern Asia is currently being completed, but the difficulty of obtaining support for large-scale taxonomic revisions means that, at present, funds are not available to publish this important work, despite the dramatic potential consequences of not doing so

References:

1. Bokonon-Ganta, A., de Groote, H. & Neuenschwander, P. 2002. Socio-economic impact of biological control of mango mealybug in Benin. Agriculture, Ecosystems and Environment 93: 367-378. 2. Commonwealth Institute of Biological Control (1991) Annual Report for 1990. 80 pp. Commonwealth Institute of Biological Control, Ascot, UK. 3. Neuenschwander, P. 2003. Biological control of cassava and mango mealybug in Africa. Pp.45-59 in: Biological Control in IPM Systems in Africa. Neuenschwander, P., Borgemeister, C. & Langewald, J. (eds). CABI Publishing, Wallingford, UK. 4. Watson, G.W. (1999) The role of taxonomy in biological control. Pp. 1-6 in: Pros. Kongres Perhimpunan Entomologi Indonesia V dan Simposium Entomologi: Pengelolaan Serangga Secara Berkelanjutan [Proceedings of the Fifth Congress of the Indonesian Entomological Society: Sustainable Insect Management], Bandung, 24-26 Juni 1997 (plenary paper). 5. Williams, D.J. (1986) Rastrococcus invadens sp. n. (Hemiptera: Pseudococcidae) introduced from the Oriental Region to West Africa and causing damage to mango, citrus and other trees. Bulletin of Entomological Research 76: 695-699. 6. Williams, D.J. (1989) The mealybug genus Rastrococcus Ferris (Hemiptera: Pseudococcidae). Systematic Entomology 14: 433-486. 7. Williams, D.J. & Watson, G.W. (1988) The scale insects of the tropical South Pacific region. Part 2. The mealybugs (Pseudococcidae). 260 pp. CAB International, Wallingford. 8. Willink, E. & Moore, D. (1988) Aspects of the biology of Rastrococcus invadens Williams (Hemiptera: Pseudococcidae), a pest of fruit crops in West Africa, and one of its primary parasitoids, Gyranusoidea tebygi Noyes (Hymenoptera: Encyrtidae). Bulletin of Entomological Research 78: 709-715.

Contributor:

1 . Dr. Peter Neuenschwander, Biological Center for Africa, International Institute of Tropical Agriculture, 08 P.B. 0932, Cotonou, Bénin. email: P.Neuenschwander@cgiar.org. 2. Dr Gillian W. Watson, Department of Entomology, The Natural History Museum, Cromwell Road, London, SW7 5BD. Tel: (+) (0) 20 7942 5741. Fax: (+) (0) 20 7942 5229. email: G.Watson@nhm.ac.uk

Regions:

Africa

Themes:

agriculture

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