Cakmak, Ibrahim ¹

¹✉ Aydın Adnan Menderes University, Faculty of Agriculture, Department of Plant Protection, Aydın, Türkiye.

2026 - Volume: 66 Issue: 1 pages: 113-117

Original research

Keywords

Abstract

Introduction

The fig (Ficus carica L.) is one of the earliest domesticated fruit species and remains a crop of major economic importance. Dried figs are valued for their high energy and mineral content and constitute a major export commodity for Türkiye, which accounts for nearly half of global production. Turkish dried figs are exported to more than 100 countries, with production concentrated in the Aegean Region, particularly Aydın and İzmir provinces, where climatic conditions are highly suitable for drying and fruit quality (Akşit et al. 2003; INC 2024).

Mites are among the most common and damaging arthropods infesting dried figs during storage. Their feeding activity and contamination reduce product quality, promote fungal and bacterial development, and may cause unpleasant odors and health problems in consumers. Infested consignments are frequently rejected during export inspections, resulting in considerable economic losses (Özer et al. 1989; Hubert et al. 2011; Dizlek et al. 2019). Due to their minute size, infestations often remain unnoticed until severe contamination has occurred (Hubert et al. 2011).

In Türkiye, Carpoglyphus lactis (L.) and Tyrophagus putrescentiae (Schrank) (Acari: Acaridae) are the most prevalent mite species associated with dried figs (Özer et al. 1989; Dizlek et al. 2019). These cosmopolitan acarid mites infest a wide range of stored products and can rapidly complete their life cycle under the warm and humid conditions typical of fig storage facilities, thereby posing a persistent risk to product quality and export reliability.

To prevent arthropod infestations, dried figs are routinely fumigated prior to processing and export. One of the most widely used fumigants in Türkiye is Eco2fume®, a commercial gas mixture containing 2% phosphine (PH₃) and 98% carbon dioxide (CO₂). This fumigant is widely applied worldwide for the control of stored-product insect pests in various commodities, including dried fruits, and is officially registered in Türkiye for the control of several insect species in dried figs at a dose of 1000 ppm (69.5 g/m³) (Cavasin et al. 2001; BKU 2025). However, Eco2fume® is not registered against mites, and information on its acaricidal efficacy is lacking. Despite its widespread use, exporters have recently reported the presence of live mites in fumigated dried-fig consignments, suggesting that protocols optimized for insect control may not be sufficient for mites.

Given the economic importance of dried-fig exports and the dominance of C. lactis and T. putrescentiae as storage pests, it is essential to evaluate whether the standard phosphine-carbon dioxide fumigation provides effective mite control under commercial conditions. Therefore, this study assessed the efficacy of Eco2fume® at four concentrations (500 ppm, 700 ppm, 1000 ppm and 1400 ppm) against C. lactis and T. putrescentiae infesting dried figs. Mortality of mobile stages and egg-hatching inhibition were evaluated under industrial fumigation conditions to determine whether current application rates ensure reliable mite control.

Materials and methods

Mite cultures

Carpoglyphus lactis was obtained from the Acarology Laboratory, Department of Plant Protection, Uludağ University and Tyrophagus putrescentiae was collected from predatory mite cultures at Aydın Adnan Menderes University. Both species were reared in plastic containers (5.5 × 6 cm) containing a 2 cm-thick layer of plaster mixed with activated charcoal (7:1), with ventilation holes covered with mite-proof gauze (Cakmak and da Silva 2018). Two dried figs were placed in each container, and mites of mixed developmental stages were transferred onto the fruits using a fine brush. Cultures were maintained in a dark incubator (MIR-254 Sanyo, Japan) at 25 °C and 65 ± 10% relative humidity.

Fumigant treatment

A phosphine–carbon dioxide fumigant (2% phosphine + 98% CO₂, Eco2fume®) registered in Türkiye for insect control in dried figs at a dose of 1000 ppm (69.5 g/m³) was used as the operational reference (BKU 2025). The shortest approved exposure duration (24 h) was selected to reflect standard commercial fumigation practice. Temperature and relative humidity were continuously recorded at 10-min intervals using dataloggers (Hobo U12-013, Onset Computer Corporation, Massachusetts, USA) to ensure compliance with label requirements.

Fumigation efficacy was evaluated at four concentrations (500, 700, 1000 and 1400 ppm) in commercial fumigation chambers at the Osman Akça Fig Processing Factory (Köşk district, Aydın, Türkiye). Chambers were insulated, unheated, and kept dark, consistent with commercial storage conditions. For each mite species, three dried fig fruits from laboratory cultures were placed in Petri dishes, each containing at least 1000 individuals of mixed developmental stages (egg to adult), confirmed under a stereomicroscope (Leica EZ4). One Petri dish per species was placed in each fumigation chamber, and each fig fruit was considered a biological replicate.

Eco2fume® was introduced into the chambers, and applied gas quantities were verified by weighing. Control samples were maintained under identical environmental conditions without fumigant exposure. During fumigation, chambers contained an average dried fig load of 350–400 kg/m³.

Post-treatment handling and mite assessment

After fumigation, samples were transferred to the laboratory and incubated in darkness at 24 °C for up to 168 h. Knockdown was assessed immediately after chamber opening (0 h). Survival and mortality of mobile stages and egg hatch were recorded at regular intervals up to 168 h under a stereomicroscope. Mites were considered dead when no movement was observed after gentle mechanical stimulation with a fine brush.

Statistical analysis

Knockdown at 0 h and mortality of mobile stages at 24 and 48 h were analyzed by one-way ANOVA, and means were separated using Tukey's HSD test (SPSS 2023).

Results and discussion

In the control treatment, all developmental stages of both mite species, including eggs and mobile stages, remained viable throughout the experimental period, and no mortality or developmental abnormalities were observed. This confirms that the experimental conditions themselves did not adversely affect mite survival.

Eggs of both Carpoglyphus lactis and Tyrophagus putrescentiae were examined at all fumigation doses (500, 700, 1000, and 1400 ppm) at regular intervals up to 168 h after chamber opening. No egg hatching was detected at any observation time or dose, and all eggs remained nonviable throughout the monitoring period, indicating complete inhibition of egg hatch. These results demonstrate that Eco2fume® was able to exert ovicidal activity under commercial fumigation conditions. From a mechanistic perspective, the observed egg mortality suggests that phosphine–carbon dioxide fumigants can effectively penetrate the dried fig matrix and reach egg deposition sites, despite the generally higher tolerance of mite eggs to fumigants. The presence of carbon dioxide may enhance fumigant efficacy by acting synergistically with phosphine, increasing respiratory activity and facilitating gas diffusion in arthropods (Armstrong et al. 2014; Constantin et al. 2020). Such a synergistic interaction likely contributed to the consistent suppression of egg hatch observed across all tested concentrations.

Eco2fume® fumigation caused clear dose-dependent knockdown and mortality in the mobile stages of both mite species. Complete knockdown and 100% mortality within 24 h were achieved at 1000 and 1400 ppm for both C. lactis and T. putrescentiae. Mobile stages were monitored throughout the 168 h observation period; however, as no further mortality was observed beyond 48 h, only data up to 48 h are presented in Table 1. In contrast, treatments at 500 and 700 ppm revealed marked species-specific responses: although high knockdown rates were observed immediately after chamber opening—particularly in T. putrescentiae—mortality at later assessment times declined substantially, especially in C. lactis, indicating recovery of temporarily immobilized individuals. These findings highlight the importance of distinguishing between initial knockdown and true mortality when evaluating fumigant efficacy.

The dose–time patterns observed at 500 and 700 ppm suggest that extended exposure periods could potentially increase mite mortality; however, under commercial dried-fig processing conditions, fumigation periods longer than 24 h are generally impractical because of limited chamber capacity and the need to maintain production flow. Consequently, despite the apparent short-term knockdown observed at lower doses (Table 1), the present results identify 1000 ppm as the minimum effective concentration ensuring complete mite control within operational constraints. This dose also corresponds to the registered application rate for insect control in Türkiye (BKU 2025), allowing simultaneous and reliable management of both insect and mite pests without increasing the risk of export rejection.

Environmental conditions recorded in the fumigation chambers showed that average temperatures ranged between 25.4 and 26.2 °C across all treatments, slightly below the 28 °C recommended on the Eco2fume® label for a 24 h exposure period. Despite this, complete control of both mite species was achieved at the recommended commercial dose. This finding indicates that Eco2fume® retains strong acaricidal activity within this temperature range, provided that chambers are adequately sealed and exposure durations are respected. According to information communicated by the manufacturer, Eco2fume® can remain effective against insect pests at temperatures as low as 24 °C under optimal application conditions, which is consistent with the outcomes observed in the present study.

Reports of live mites detected in fumigated dried-fig consignments are therefore more likely attributable to suboptimal application conditions rather than insufficient intrinsic efficacy of the fumigant. Reduced temperatures, shortened exposure periods, premature chamber opening, or inadequate insulation may all reduce fumigation performance, allowing temporarily immobilized mites to recover and survive. From a practical perspective, the present results confirm that Eco2fume® represents a reliable and environmentally safer alternative to methyl bromide, which has been phased out due to its ozone-depleting potential (UNEP 2019). Its stabilized formulation enables controlled fumigation under commercial conditions and supports effective postharvest management of storage mites in dried figs and other high-value dried commodities (Nayak et al. 2020).

In conclusion, under realistic commercial conditions and a 24 h exposure period, Eco2fume® at 1000 ppm ensures complete control of both egg and mobile stages of C. lactis and T. putrescentiae. Lower doses induce substantial knockdown but do not guarantee complete mortality within operational constraints, highlighting the importance of adhering to recommended application parameters to minimize the risk of mite survival and export rejection.

Acknowledgements

The author wishes to express sincere appreciation to Nabi Alper Kumral for providing the Carpoglyphus lactis culture, and to Arda Çağlayan, Çağlar Çağlayan and İsmail Acar for their valuable technical assistance and support during the conduct of this research.

Funding

No specific funding was received for this study.

Competing interests

The authors declare no competing interests.

Data availability

All datasets generated and analyzed in this study are available from the corresponding author upon reasonable request.

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