Pg. 39-40 Exposure of Natal Fruit Fly, Ceratitis Rosa Karsch, to Litchi Export Conditions

Two fruit fly species are known to attack litchi fruit in South Africa, namely the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) and the Natal fruit fly, Ceratitis rosa Karsch. Experiments were conducted to determine if C rosa could survive litchi export conditions. Litchi fruit are not an ideal host for fruit fly development and therefore loquat fruit were used. Naturally infested loquat fruit were stored for 21 days at 1°C. In the next experiment similar fruit were fumigated with sulphur dioxide and afterwards placed in cold storage. Thirdly fruit with different stages of C rosa were placed in cold storage. Lastly fruit were exposed in cages to C rosa and placed in cold storage. Each experiment had a control which was not placed in cold storage. No live C rosa were present after cold storage although survival occurred in the controls. Cold treatment seems to be an effective method for disinfestation of C rosa in litchi fruit.

Summary:

• Two fruit fly species attack litchis in South Africa: Mediterranean fruit fly (Ceratitis capitata) and Natal fruit fly (Ceratitis rosa), with C. rosa dominant in some areas.
• Litchi fruit is not an ideal host for fruit fly development, so loquat fruit was used as an alternative host for experiments.
• The study tested whether C. rosa could survive typical South African litchi export conditions, which involve fumigation with sulfur dioxide and cold storage at 1°C for about 21 days.
• Four experiments were conducted:
  • Naturally infested loquat fruit stored at 1°C for 21 days.
  • Sulfur dioxide fumigated and cold-stored loquat fruit.
  • Different developmental stages of C. rosa in cold storage.
  • Loquat fruit exposed to C. rosa adults and then cold-stored.
• Controls (non-cold-stored fruit) showed survival of C. rosa larvae and pupae.
• No live C. rosa larvae or pupae survived the cold storage treatments in any of the experiments.
• Cold treatment alone was effective in disinfesting C. rosa from the fruit.
• Litchi fruit, unlike some other fruit, tolerate cold storage well, making cold treatment a viable sterilization method for export.
• The study supports that export conditions in South Africa (fumigation plus cold storage) effectively prevent survival of C. rosa, reducing quarantine risk for importing countries.
• The study references past work on cold treatments for fruit fly disinfestation and confirms that cold tolerance of fruit flies and fruit quality are key factors for success.