Post‐harvest disinfestation of Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) in mango using hot‐water treatments

Abstract

Mango, Mangifera indica L. (Anacardiaceae), is one of the most important fruits in Africa, providing household nutrition and economic development opportunities for millions of growers across the continent. In Kenya, over 80% of mango production is carried out by smallholders who produce this crop for both the domestic and the export markets. Despite its importance, mango production is hampered by several constraints, including infestation by fruit flies, especially the exotic Bactrocera dorsalis. In addition to its direct damage to fruits, the high quarantine status of the pest restricts the export of fruits and limits access to lucrative markets, impacting negatively on export earnings. To facilitate access to export markets, post‐harvest management measures such as hot‐water treatment are required to ensure quarantine security. Internationally, this level has been set as either 99.99% (Probit 8.7) or 99.9968% (Probit 9). In developing a protocol, the development of immature life stages of B. dorsalis in ‘Apple’ mango was established. Using this information, infested mangoes harbouring the different immature life stages were subjected to a hot‐water treatment of 46.1°C for four different times, and the egg mortality and larval mortality were determined. The third‐instar life stage was the most heat tolerant, followed by second‐ and first‐instar larvae and the egg stage, respectively. The immersion time of 81.47 min (95% CL 75.77–87.18) was established as the time required to achieve 99.99% security level. In the validation experiment, there were no survivors from the 51,101 third‐instar individuals treated in ‘Apple’ mango weighing 400–500 g. Furthermore, there were no survivors from the 44,651 third instars exposed to 46.1°C for 68 min. These results provide sound evidence that the shorter treatment duration is an effective post‐harvest disinfestations treatment against B. dorsalis, and should facilitate access to export markets for mango fruits from Africa.

Advances in Postharvest Disinfestation of Fruits and Vegetables Using Hot Water Treatment Technology-Updates from Africa

“…Treatment protocol Target Reference that Mozambique subjects its mangoes for export to South Africa, to HWT at 47°C for 12 minutes, [67] but it is unlikely that this treatment is adequate to disinfest any fruit fly or insect pest of mango. It has been demonstrated that at 46.1°C for durations less than 68 minutes, B. dorsalis larvae can still survive in apple mango variety weighing up to 500 g [19]. The most thermotolerant stage of development of this pest was only killed by continuous exposure to hot water treatment for a minimum of 68 minutes.…”

“…Further trials were conducted in Kenya on Apple mango at a temperature of 46.1°C for 81.47min with 95% confidence limits set at 75.77-87.18 min [19]. However, efficacy data consistently showed that 68 mins were equally effective in disinfesting mangoes of up to 500 g against the devastating B. dorsalis.…”

“…Various postharvest treatment technologies are available for adoption in providing quarantine assurance that fruits and vegetables are free from devastating pests not found in importing countries. These include controlled atmospheres [15], irradiation [16] Vapor Heat Treatment (VHT) [17], cold treatment [18], and immersion Hot Water Treatment (HWT) [19,20] among others. Though the treatments may achieve the objective of disinfecting and disinfesting fruits and vegetables, they are also known to affect the physical and chemical properties of treated commodities [21].…”

Post-Harvest Treatments and Related Food Quality

“…Therefore, further post-harvest treatments in developing countries like Africa and Asia, e.g. hot water treatment, modified atmosphere packaging, and fermentation are necessary to maintain food security and world nutrition (Habwe et al 2008;Wafula et al 2016;Ndlela et al 2017). The different post-harvest treatments described in the following sections are useable globally and not only in developing countries.…”

A comparison of postharvest quality of breadfruit (<i>Artocarpus altilis</i>) after disinfestation with hot air or hot water treatments

“…Similar treatments involving hot water (HWT) are used for fruit fly disinfestation in a range of crops including mango (Mangifera indica) (Sharp et al 1989a;Sharp et al 1989b;Nascimento et al 1992;Ndlela et al 2017).…”