Pg. 29-31 Invasive fruit fly species in Africa and the possible threat to the subtropical fruit industry in South Africa

Fruit flies (Diptera: Tephritidae) includes about 4 300 species in almost 500 genera. It is amongst the largest families of Diptera and one of the most economically important. Some of these species have become pests in areas far removed from their initial native range. 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 is completed within the fruit, 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. In Africa there are approximately 950 known fruit fly species, which belong to 150 genera. Approximately 50 species in Africa are of economic importance. Most species which attack commercially grown fruit crops belong to two genera only, namely Ceratitis and Dacus. A few species belong to other genera, such as the coffee fruit flies (Trirhithrum spp.) which are close relatives of Ceratitis, or to the genus Bactrocera, which are close relatives of Dacus.

Summary:

• Fruit flies (family Tephritidae) are a large and economically important group, with ~4,300 species globally; around 950 species are known in Africa, with about 50 economically significant.
• Most economically important fruit flies affecting commercial crops in Africa belong to the genera Ceratitis and Dacus; the Asian genus Bactrocera includes invasive species with high pest potential.
• Several invasive Asian Bactrocera fruit flies have been introduced into Africa, including the melon fruit fly (Bactrocera cucurbitae), first recorded in the 1930s, which affects cucurbits and various other fruits.
• Other invasive Bactrocera species include the solanum fruit fly (Bactrocera latifrons) found in East Africa, and the peach fruit fly (Bactrocera zonata), recorded in northern Africa but not yet south of the Sahara.
• The invasive fruit fly Bactrocera invadens, originating from the Indian subcontinent, was first detected in Africa in 2003 and has rapidly spread to many African countries including Angola, Ghana, Tanzania, and others.
• Bactrocera invadens is highly polyphagous, attacking cultivated fruits like mango, guava, banana, citrus, and non-cultivated plants; its preference is higher at low altitudes.
• Life cycle studies show rapid development, high fecundity, and adult longevity, contributing to its invasive success in Africa.
• Its presence threatens native fruit flies and causes direct damage and trade restrictions due to quarantine regulations.
• South African subtropical fruit industry is at risk from B. invadens invasions due to possible expansion or accidental import of infested fruit.
• Current control strategies include monitoring, bait sprays, sanitation, male annihilation, and potential sterile insect technique; coordinated surveillance programs are ongoing.
• The article emphasizes the urgency for South African growers to participate in surveillance and control efforts to mitigate the threat and protect exports, especially of mango, avocado, guava, and papaya.
• Litchi is currently not listed as a host for Bactrocera invadens, but the range of affected fruits includes many commercially important crops.