INSECT COLUMN
Natal fruity (Diptera: Tephritidae) The Natal fruit fly (Ceratits rosa) is an indigenous polyphagous pest the attacks several commercial fruits, including a wide range of wild fruit species. Ceratitis rosa belongs to a complex of cryptic species and was recently split into two species, C. rosa and Ceratitis quilicii. Host plants of the Natal fruit fly include avocado, peach, plum, stone fruit, apricot, guava, mango, apple, citrus, cashew nut and prickly pear. Its distribution is mainly restricted in eastern and southern Africa. In South Africa, C. rosa is distributed in the northern and eastern parts and along most of the country's coastal areas (including the southwestern areas). At the same time, it is largely absent in the drier inland areas and arid regions. C. rosa is more abundant in hot areas, while C. quilicii is more abundant in cooler areas.
Figure 1: Adult of the Natal fruit fly. Source: https://www.projectnoah.org/spottings/18588034 Figure 2: Mature avocado fruit with star-shaped cracks surrounded by white powder, indicating the oviposition (sting) marks of the Natal fruit fly Source: http://www.avocadosource. com/wac1/wac1_p075.pdf
Nozibusiso Maphumulo IPM-PROGRAMME, NORTH-WEST UNIVERSITY, POTCHEFSTROOM
Natal fruit fly classification: Class: Insecta (insects) Order: Diptera (flies) Family: Tephritidae Genus: Ceratitis Species: rosa
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hese species are of phytosanitary importance and can become invasive pests outside their native range, and in other parts of the world, especially in tropical and subtropical areas. The common mode of dispersal and introduction is through commercial shipments of fruits that are infested with larvae. It can also be spread through the luggage of travellers. Females of the Natal fruit fly become sexually mature and lay eggs five days after emergence from pupae and when conditions are favourable. Eggs are laid inside the ripening fruit under the skin surface. Oviposition (sting) sites appear as small brown spots on the surface of the fruit. They lay one to more than 20 eggs. Larvae hatch between 2 to 3 days and develop inside the fruit, and has three larval stages. Larvae leave the fruit once it has matured after 7 to 40 days, fall into the ground, and pupate below the soil's surface. Adult fruit flies emerge from the pupae after 8 to 40 days. Its life cycle ranges from three to four weeks under favourable conditions and two to three months in winter. It has three to six generations per year, depending on the weather and availability of resources. The length of the fruit fly adult is approximately 8 mm. They are brown in colour with reddish-purple eyes. The wings have a pattern of brown bands. Eggs are white, smooth and banana-shaped with a length of 1 mm. First-instar larvae are
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minute and translucent with no visible head, while 2nd and 3rd-instars are white to cream-coloured. Mature larvae are 9-11 mm in length. Larvae are typically those of fly maggots – they do not have legs, and the body tapers from the posterior to the anterior end. Blackmouth hooks are visible in 2nd and 3rd-instar larvae. Pupae have a cylindrical shape with rounded ends and a length of 4- 6 mm. Pupae are initially straw-coloured and then turn dark reddish-brown. Natal fruit fly causes damage on both young and older fruits of crops such as avocado, citrus, etc. The larvae feed inside the fruit while tunnelling to the centre of the avocado fruit. Feeding damage often leads to infections by micro-organisms and secondary pests. Larvae cause intensive damage to commercial fruit crops. This then results in heavy losses of fruits. For example, damage symptoms on avocado are noticeable by lesions that appear as puncture marks surrounded by a white powdery substance when the fruit is about golf-ball size. Star-shaped cracks occur in the skin as the fruit develops. When the skin around the lesion is removed, the underlying tissue appears bruised. Traps baited with male lures can be used to monitor this pest. Natal fruit fly can be controlled through sanitation by picking up and burying fallen fruits to avoid attracting fruit flies. Biological control agents for the fruit flies include entomopathogenic bacteria, fungi, nematodes, ants and spiders. Chemical control can be achieved through fruit fly baits using a protein attractant mixed with synthetic or natural insecticides. Sterile Insect Technique (SIT) can also be used to manage fruit fly populations. Enquiries: mashimanenozi03@gmail.com
VEGETABLES & FRUIT | NOVEMBER • DECEMBER 2021
