A Review of the Biological Control of Agricultural Pests in the Seychelles

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Guy, L.J.F.
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Prior to 1936, when D. Vesey-Fitzgerald started his investigation on Seychelles coconut scale insects, work on the biological control of agricultural pests in the Seychelles had only consisted in the introduction of entomogenus fungi, one of which, Cephalesporium lecanii has established itself and is common on coccids of cinnamon, citrus and coffee, and is considered responsible for the successful control of the coffee green scale Coccus viridis (Green) at higher altitudes in the Seychelles. Fitzgerald's investigation revealed that four species of scale insects, lschnaspis longirostris, Sign, Pinnaspis buxi, Bouche, Chrysomphalus ficus, Ashm and Eucalymnatus tessellatus, Sign. Were especially prevalent on coconut in the Seychelles. As no effective natural enemies of these coccids existed locally, Fitzgerald introduced four species of coccinelIid predators from East Africa and one species from India to prey on them. They were: Chilocorus distigma, Klug., Chilocorus wahlbergi, Muls., Chilocorus nigritus, F., Exochol11us ventralis, Gerst and Exochomus {lavipes Th. Of these C. wahlbergi did not establish itself while C. nigritus, the species from India, became and still is the commonest species. Fitzgerald also introduced a sixth coccinellid from Mauritius, Rodolia cardinalis, Muls., to prey on lcerya seychellarum, Westw., the mealy-bug of fruit trees. Although not as successful as the other species, Rodolia has been useful in keeping in check lcerya. The consequence of these introductions was the spectacular control, in a matter of months, of the scale insect population of the coconut groves, with as a result a substantial increase in the coconut crop of the islands from the year 1940 onwards.
East African Agricultural and Forestry Journal, XXIV (No. 4), pp. 254-256