Cold Disinfestation of Zeugodacus tau (Diptera: Tephritidae) on Oranges Using Artificial Infestation Method

TL;DR

The study found that a 22-day cold treatment at 1.8°C effectively kills Zeugodacus tau fruit flies in oranges, helping to prevent their spread through international trade.

Contribution

The study provides new evidence for a specific cold treatment protocol to control Zeugodacus tau in citrus fruits, supporting phytosanitary standards.

Findings

A 22-day cold treatment at 1.8°C resulted in no Z. tau survivors in oranges.

Z. tau third instar larvae showed the highest cold tolerance among developmental stages.

Z. tau requires longer treatment times at higher temperatures for other host fruits to ensure quarantine security.

Abstract

Cold treatment has been employed since the early 20th century to ensure phytosanitary control of fruit flies in various fruits. A cold treatment protocol for Zeugodacus tau must be developed to improve global fruit trade. Therefore, cold disinfestation trials were carried out with Z. tau infesting oranges through artificial infestation. There were no survivors among 9180 individuals of Z. tau in oranges treated at 1.8 °C for 22 days. This data provided support for the application of the 22-day treatment at ≤1.67 °C as an additional safety measure. Such a measure mitigates the risk of introduction and establishment of Z. tau through imported citrus. However, for other susceptible hosts of Z. tau, the cold treatment schedules need 23 d at 1.75 °C or 25 d at 2.34 °C with larval endpoint to achieve quarantine security. These results will provide sufficient evidence for the development of phytosanitary treatments against Z. tau under ISPM 28, thereby facilitating trade in its host fruits.

Zeugodacus tau, an economically important fruit fly species, exhibits a preference for infesting the fruits of cucurbitaceae, but it has also been reared from the fruits of several other plant families. Phytosanitary treatments are needed to ship the fruit from some of these host plants out of areas where populations of the fruit fly exist. Based on the guidelines for the development of cold disinfestation treatments for fruit fly host commodities, proposed by the International Plant Protection Convention (IPPC), the cold disinfestation trials were carried out with Z. tau infesting oranges through artificial infestation. The results showed that the third instar of Z. tau was the most tolerant stage among all developmental stages. No survivors were found among 106,204, 96,168, and 9180 individuals of Z. tau in oranges treated at 1.75 °C for 23 d, 2.34 °C for 25 d, and 1.8 °C for 22 d, respectively. These results support for the application of the 22-day treatment at ≤1.67 °C as an additional safety measure. Such a measure mitigates the risk of introduction and establishment of Z. tau through imported citrus. However, for other susceptible hosts of Z. tau, the cold treatment schedules against Z. tau required to achieve quarantine security with larval endpoint would need to be 23 d at 1.75 °C or 25 d at 2.34 °C. These results also indicated that Z. tau exhibits the highest cold tolerance among the other tephritid species for which cold treatment have been reported.

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