Situation of Bactrocera zonata in Réunion
In the Mascarene islands, Bactrocera zonata (Diptera, Tephritidae – EPPO A1 quarantine pest) was first detected in 1987 in Mauritius where it rapidly replaced other fruit flies. This triggered a surveillance programme in Réunion. B. zonata was first identified there in 1991, although it seems likely that it had been confused for some time with the indigenous B. montyana. Since 2000, a significant increase of B. zonata populations has been noticed in the north of the Island. To control the pest, the island was divided into 2 zones: a northern part where most captures were made and an eradication programme was initiated, and a southern part where captures remained rare and a surveillance programme was set up. In the eradication zone, methyl-eugenol traps (including an insecticide) were placed along a 1 x 1 km grid and checked every week. Male annihilation technique was used and ‘killer-blocks’ containing methyl-eugenol and malathion were placed (4-10 blocks/ha, renewed every 3 months). Hot-spot treatments were also made (protein bait + malathion) around the sites where captures had been made. In addition, host fruits (Mangifera indica, Prunus persica, Psidium guajava, Terminalia catappa) showing punctures were collected to check the presence of B. zonata. In the south part of the island, more than 100 traps were placed in orchards, near the main fruit and vegetable markets, and near the seaport. When males were captured, trapping was intensified and, if new findings were made, control actions (use of killer-blocks) were undertaken. After two years of these intensive measures, it was unfortunately observed that B. zonata had established near St Denis (although at low populations), and continued to progress outside the eradication zone into the surveillance zone where it was found in numerous places. In May 2001, the eradication campaign was abandoned in the north of the island. At the end of 2001, the highest populations were found in the north-east (St Denis, St Marie, St André), north-west (La Possession, Rivière des Galets, St Paul) and in the west. Observations made on host fruits showed that B. zonata could multiply on: Citrus paradisi, Citrus reticulata, Mangifera indica, Mimusops elengi, Persea americana, Psidium guajava, Punica granatum, Terminalia catappa, Syzygium jambos, Ziziphus jujuba. Nevertheless, intensive control will continue to be applied in Réunion to contain the pest. Studies on host plants, ecology and biology of B. zonata, as well as on efficacy of chemical treatments will be carried out, and more information will be provided to the growers. The situation of B. zonata in Réunion can be described as follows: Present, found mainly on the north and west of the island, under official control.
Hurtrel, B.; Quilici, S.; Jeuffrault, E.; Manikom, R.; Georger, S.; Gourdon, F. (2002) Etat de siège contre la mouche de la pêche, Bactrocera zonata. Bilan des opérations de lutte menées à la Réunion.
Phytoma – La Défense des Végétaux n° 551, 18-21.