Fruit flies and avocado production - a world perspective

38 INTRODUCTION Fruit fl ies (Diptera: Tephritidae) includes about 4 300 species in almost 500 genera (White, 2006). It is amongst the largest families of Diptera and one of the most economically important. The larvae of many species develop in the seed bearing organs of plants. Several species are known to attack different types of commercially grown crops, causing considerable damage. The female punctures the fruit with her ovipositor and deposits eggs within the host fruit. Larval development within the fruit causes direct damage, which as a result may become rotten. Larvae then drop to the soil to pupate. Losses are due to direct feeding damage and also to loss of export markets as a result of quarantine restrictions imposed by importing countries free of these pests. Countries free of the fruit fl y pest can require commercial fruits to undergo protective and postharvest treatments prior to export. With globalisation and the increase inter-continental movement of people it is likely that the problem of invasive fruit fl y species will increase. The increased international trade in fresh commodities will also contribute to the risk of new species being introduced into novel areas. There are about 100 fruit fl y species that are considered pests (White & Elson-Harris, 1994; White, 2006). These mostly belong to fi ve genera, namely Bactrocera Macquart, Ceratitis MacLeay, Dacus Fabricius, Anastrepha Schiner and Rhagoletis Loew. The avocado, Persea americana Mill. (Lauraceae) is associated with three fruit fl y genera, i.e. Bactrocera, Ceratitis and Anastrepha. The genus Bactrocera is a large genus in Asia and Oceania and comprises of 520 described species (Norrbom, 2004). Certain species are regarded as some of the most destructive pests of fruit and vegetables world-wide (White & Elson-Harris, 1994). Bactrocera species are well documented as invaders and rank high on quarantine lists. In Africa, only a few indigenous species are known and only the olive fruit fl y, Bactrocera oleae (Rossi), which is a notorious pest of cultivated olives in the Mediterranean regions, is of economic importance (White & Elson-Harris, 1994; White, 2006). However, four Asian Bactrocera pest species were introduced to Africa, i.e. the melon fl y, Bactrocera cucurbitae (Coquillett); the Solanum fruit fl y, Bactrocera latifrons (Hendel); the peach fruit fl y, BacT Grové and MS De Beer