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Article

Phosphine Susceptibility Screening of Three Different Stored Product Beetle Species by Using Three Diagnostic Techniques

by
Maria K. Sakka
1,*,
Marie-Carolin Götze
2 and
Christos G. Athanassiou
1
1
Laboratory of Entomology and Agricultural Zoology, Department of Agriculture, Crop Production and Rural Environment, University of Thessaly, Phytokou Str., 38446 Volos, Greece
2
Detia Freyberg GmbH, Dr.-Werner-Freyberg-Str. 11, 69514 Laudenbach, Germany
*
Author to whom correspondence should be addressed.
Agriculture 2025, 15(17), 1904; https://doi.org/10.3390/agriculture15171904
Submission received: 17 April 2025 / Revised: 25 August 2025 / Accepted: 4 September 2025 / Published: 8 September 2025
(This article belongs to the Section Crop Protection, Diseases, Pests and Weeds)
Versions Notes

Simple Summary

In this study, we evaluated phosphine resistance in 12 populations of three different stored product insect species, including Oryzaephilus surinamensis, Rhyzopertha dominica, and Cryptolestes ferrugineus, and used three different diagnostic techniques, namely the Food and Agriculture Organization (FAO) protocol, dose–response bioassay, and Phosphine Tolerance Test Kit (PTT). The results showed that all populations of O. surinamensis and R. dominica were found to be resistant according to the FAO protocol. The study investigated similar results among the diagnostic techniques and we suggest the design of a new “global” evaluation protocol.

Abstract

Phosphine resistance represents a major challenge for stored product protection worldwide. In this study, we evaluated populations of Oryzaephilus surinamensis, Rhyzopertha dominica, and Cryptolestes ferrugineus collected from different regions using three diagnostic protocols: (i) the FAO test (30 ppm for 20 h); (ii) a dose–response bioassay (50–1000 ppm for 3 d); (iii) the Phosphine Tolerance Test (3000 ppm for up to 270 min). Results indicated that while several O. surinamensis populations remained susceptible, all tested populations of R. dominica and C. ferrugineus were resistant. The three protocols produced comparable outcomes, supporting their reliability for diagnosing resistant populations. This is the first study to simultaneously compare three diagnostic approaches across multiple beetle species, providing the basis for a harmonized global diagnostic framework. These findings underscore the need for continued monitoring and highlight the importance of standardized tools for resistance management.

1. Introduction

Phosphine remains the cornerstone fumigant for the protection of stored commodities worldwide, largely because of its low cost and ease of use [1]. It is applied across a wide spectrum of products, including dried fruits, pulses, tobacco, and especially cereal grains [2,3]. However, decades of extensive reliance on phosphine have resulted in the emergence of resistant insect populations in many regions, such as the United States [4,5,6], Australia [7,8], China [9,10], and several European countries [11,12,13,14]. For example, Sakka and Athanassiou [11] evaluated populations of three different species of the genus Sitophilus from Europe and found that some populations survived at concentrations that were usually lethal for most stored product insect species. Opit et al. [3] evaluated populations from different parts of Oklahoma, USA, and found that most populations of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), and the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostryhidae), were resistant to phosphine. More recently, Nayak et al. [15] reported that 29 and 50% of R. dominica and T. castaneum populations, respectively, they had sampled from northern tropical Australia were diagnosed as strongly resistant to phosphine. Earlier studies from Australia revealed the presence of stored product insects that are strongly resistant to phosphine, i.e., they were able to survive at extremely high concentrations, which are usually effective in erasing most populations [1,15]. In addition, there are recent data that indicate the occurrence of phosphine resistance in several populations of stored product insects from Europe, but there are still no indications of strong resistance in European populations [11,12,13,14].
Several laboratory protocols are available for detecting and grading phosphine resistance. Among them, the Food and Agriculture Organization (FAO) method is the most frequently used, as it provides a simple and reliable means to distinguish resistant from susceptible populations [16]. In this test, insects are generally exposed to 30 ppm phosphine for a 20 h period, and mortality is assessed 7 or 14 days later [3,11,12,17,18]. Using this protocol with minor adjustments, Holloway et al. [18] reported resistant populations of the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) in Australia, while Pimentel et al. [19] found that 20 out of 22 populations of the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), were resistant. Accordingly, the FAO test serves as a commonly used screening tool to provide early indications of resistance in stored product beetle populations [20,21]. A protocol that can separate weak from strong resistance is the dose–response bioassay. In this bioassay, insects are exposed to different concentrations at specific exposures [17,22,23]. For instance, Gourgouta et al. [24] tested different life stages of the khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), at different concentrations ranging from 50 to 1000 ppm for 3 days, and provided data for the dissimilar susceptibility of eggs as compared to the other life stages. Afful et al. [25] tested different R. dominica populations using the dose–response bioassay and found that 48 h at 730–870 ppm would control strongly resistant populations. The dose–response bioassay can be used as an additional diagnostic, following that of the FAO protocol, in order to scale and quantify the different populations according to their susceptibility to phosphine.
Another series of methods known as “rapid tests”, which are based on immediate effects right after the initial insect exposure, have been developed by several research groups [12,14,17]. For instance, Nayak et al. [26] tested strong resistance in populations of the rusty grain beetle, Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae), after exposing adults of this species for 5 h to 1436 ppm of phosphine. Most recently, the Phosphine Tolerance Test (PTT; Detia Degesch GmbH, Laudenbach, Germany) has been used by several researchers with good results, as a diagnostic of an initial screening for a large number of insect species and populations [12,14,17,27]. The PTT is based on the exposure of adults of stored product insects to 3000 ppm of phosphine for some minutes (species specific time frames), and it is based on immobilization rather than mortality. In this way, an indication of tolerance can be obtained at a relatively short interval, without the need to expose insects for long periods, a procedure that requires a specialized laboratory [27]. In principle, for the majority of stored product beetles tested so far, results from the PTT have been found to correlate well with those obtained from the FAO diagnostic.
The present study aims to investigate phosphine resistance of stored product insects with different evaluation techniques. To our knowledge, the data regarding evaluations of the most common protocols on more than one species are limited [11,12,13,14], and considering the need to evaluate the susceptibility to phosphine in different protocols, we collected populations of the saw-toothed grain beetle Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), R. dominica, and C. ferrugineus from different areas, including Europe. To our knowledge, this is the first work that applies the FAO protocol, a dose–response bioassay, and the Phosphine Tolerance Test (PTT) in parallel across different beetle species. The comparison provides useful evidence that can support efforts to harmonize diagnostic approaches for monitoring phosphine resistance on a broader scale.

2. Materials and Methods

Populations with confirmed susceptibility to phosphine were used for each of the three species and are hereafter referred to as LB.
These laboratory colonies have been maintained for more than 20 years under controlled rearing conditions without exposure to any fumigant or insecticide, and served as reference “control” populations. In addition, six field-collected populations of O. surinamensis (L.) (Coleoptera: Silvanidae), two of R. dominica, and one of C. ferrugineus were examined for phosphine resistance (Table 1). Colonies of O. surinamensis, R. dominica, and C. ferrugineus were maintained on oats, soft wheat, and flour, respectively, at 25 °C, 55% relative humidity (RH), and continuous darkness in the Laboratory of Entomology and Agricultural Zoology (LEAZ). For all diagnostic protocols, unsexed adults of known age (7–14 days old) were used.

2.1. Evaluation of Phosphine Resistance

All populations were assessed using three different diagnostic procedures: the FAO protocol, the dose–response assay, and the Phosphine Tolerance Test (PTT). Under the FAO method, adults were subjected to 30 ppm phosphine for a 20 h exposure period. In the dose–response assay, insects were treated with concentrations ranging from 50 to 1000 ppm for 3 days (50, 100, 200, 500, 700, and 1000 ppm). The PTT was implemented according to the procedure described by Sakka and Athanassiou [11,17], with slight adjustments. Following each treatment, insects were moved to untreated Petri dishes and kept at 25 °C, 55% relative humidity, and continuous darkness for 7 additional days to assess delayed mortality and possible recovery.
In the FAO diagnostic assay, each replicate consisted of 20 adults confined in glass vials and exposed to 30 ppm phosphine at 25 °C. Phosphine was produced inside a sealed plastic canister by reacting two magnesium phosphide pellets (Detia Freyberg GmbH, Laudenbach, Germany) with 50 mL of water. Gas levels were verified by gas chromatography (Shimadzu GC-2010Plus, Kyoto, Japan) equipped with a GS-Q column (30 m × 0.25 mm i.d., 0.25 μm film; MEGA S.r.l., Legnano, Italy) and a flame photometric detector operating in phosphorus mode. After the 20 h exposure, adult insects were categorized as active, knocked-down, or unresponsive (moribund), following the criteria of Sakka and Athanassiou [11,17]. Subsequently, survivors were transferred to untreated Petri dishes and maintained for a 7 d recovery period. A population was considered resistant if active adults were still detected at the final evaluation. For the dose–response bioassay, the procedure of gas generation and experimental design was identical to that of the FAO test, but exposure concentrations were 50–1000 ppm for 3 d. Resistance was classified as follows: susceptible when no active individuals remained, weakly resistant when active individuals were observed up to 200 ppm, and resistant when survivors were present at ≥500 ppm after the 7 d post-exposure period.
In the PTT, adults were exposed to 3000 ppm of phosphine for 5, 10, 15, 20, 25, 30, 45, 60, 90, 120, 150, 180, 210, 240, or 270 min. Gas production was conducted as described above. A population was considered resistant when active individuals were recorded 7 d after exposure [17]. All assays were performed in triplicate, with three replicates further subdivided into three sub-replicates. For each replicate, phosphine was newly generated to ensure consistent exposure.

2.2. Statistical Analysis

In the FAO assay, the proportions of adults classified as active, knocked-down, or moribund were analyzed separately with an analysis of variance (ANOVA), and treatment means were compared using Tukey’s HSD test (α = 0.05). For both the dose–response bioassay and the PTT, an ANOVA was likewise applied to assess population differences. Dose–response data were further analyzed with Probit models to estimate LC90 and LC99 values, calculated on the basis of moribund individuals. All statistical analyses were performed with IBM SPSS Statistics version 26.3.

3. Results

3.1. Oryzaephilus Surinamensis

According to the FAO bioassay, the laboratory population was diagnosed as susceptible to phosphine with 100% immobilization after 20 h of exposure and complete mortality 7 days later (Table 2). For the field populations, at the same interval, survival rates were 81 and 100% for Vis17.1 and Def3.1, respectively. These populations were classified as resistant and respectively recorded with 34 and 98% of active individuals at the 7 day post-exposure interval. In contrast, no active individuals were recorded for all other field populations, and all of them were 100% immobilized after 20 h of exposure, with the exception of 3Zol, which was recorded with 0.6% of immobilized adults at the 7 day post-exposure interval.
For the dose–response bioassay, no active individuals were recorded for 1W, Pesck, 3Zol, and LB populations after 3 days of exposure and at 7 days post-exposure (Table 3). In contrast, 16 and 30% of active individuals were recorded after 7 days of exposure at 50 ppm for Vis17.1 and Def3.1 (Table 3). In general, active individuals were recorded until 200 ppm for Def3.1 and Vis17.1; after 200 ppm, most of the populations were recorded with 100% immobilized adults. LC values were only estimated for Vis17.1 (Table 4).
For the PTT, the populations of Vis17.1 and Def3.1 were recorded with active individuals that reached 16.7% after 240 min and 19.4% after 270 min, respectively (Table 5). In contrast, complete immobilization was recorded for the LB population after 5 min. Finally, for the rest of the populations tested, population 1W showed active individuals until 10 min, but there were no active individuals at the 7 d post-exposure interval (Table 5).

3.2. Rhyzopertha Dominica

According to the FAO bioassay, the laboratory population was diagnosed as susceptible to phosphine with 100% immobilization after 20 h of exposure (Table 2). Both field populations showed 87 and 16% and 80 and 32% active individuals after 20 h of exposure and 7 days later, respectively.
For the dose–response protocol, both field populations were recorded with low numbers of active individuals at 50 ppm (Table 3). At 200 ppm, mortality reached 92 and 100% for both field populations (Table 3). Nevertheless, only the population Inj showed some survival at the post-exposure period at 200 ppm. In most cases, the Probit analysis did not allow the calculation of LC values for the populations examined (Table 4).
In the PTT, for the laboratory population active individuals were recorded until 5 min, followed by complete immobilization. For the field populations, only Inj was recorded with active individuals until 60 min (Table 5). For the 9CRG, 98% of immobilization was recorded after 15 min of exposure. At 7 days post-exposure, only the population 9CRF was recorded with some active individuals.

3.3. Cryptolestes Ferrugineus

Based on the FAO protocol, the laboratory strain was classified as susceptible to phosphine (Table 2). The field population was recorded with 100% of active individuals after 20 h and at 7 days post-exposure.
In the dose–response bioassay, B1 was recorded with 100% active individuals at 50 ppm and 4% after 1000 ppm (Table 3). The LC values were estimated only for B1 (Table 4).
In the PTT, active individuals of B1 were recorded until 90 min, while 100% immobilization was recorded in the case of LB. Seven days later, 83% of active adults were noted for the field population, while there no surviving adults were recorded for LB.

4. Discussion

In this work, we assessed phosphine resistance using three established diagnostic approaches. Previous studies have also evaluated different diagnostic methods. For example, Sakka and Athanassiou [11] applied two protocols on Sitophilus spp. from various regions and reported that 13 out of 35 populations were resistant according to the FAO diagnostic. In another study, the same authors [17] compared the FAO protocol, the dose–response assay, and the PTT using Lasioderma serricorne (F.) (Coleoptera: Anobiidae), and found that all three methods produced comparable outcomes. Here, by applying the FAO, dose–response, and PTT protocols in parallel, we confirmed that most field populations were resistant to phosphine, with the exception of certain O. surinamensis populations that remained susceptible. The general agreement among methods highlights their potential to contribute towards a harmonized global diagnostic framework.
Our findings are consistent with surveillance reports from other regions where phosphine resistance has been documented [12,13]. For instance, Afful et al. [5] showed that almost all R. dominica populations from the United States and Canada were resistant, while Opit et al. [3] recorded resistant populations of the same species in Oklahoma. Similarly, all tested R. dominica populations were found to be resistant in this study. For O. surinamensis, two out of six field populations were resistant based on the FAO protocol, in agreement with earlier studies such as the report by Gautam et al. [28], who found resistance in a subset of populations. Resistance in C. ferrugineus has also been frequently reported [29,30]. Highly resistant populations have been described in the USA [30] and Australia [26,31]. Konemann et al. [30] reported resistance in all 19 C. ferrugineus populations surveyed in Oklahoma. Comparable results have been reported for R. dominica in Brazil [32] and the United States [3]. In the present study, the single C. ferrugineus population tested survived exposure to 700 ppm for 3 d, the highest level recorded among the three species examined. It should be noted that only one C. ferrugineus population was tested, which limits the extent to which our findings can be generalized for this species. Although based on only one population, this finding may reflect the presence of stronger resistance, similar to that previously reported in Australia [29,30], and further sampling is needed to confirm this.
Results from the PTT offered valuable insights into resistance dynamics. Survival remained comparatively high even during short exposures, with certain populations retaining activity after 90 min. In T. castaneum, knock-down times measured under high-concentration phosphine exposures have been demonstrated to effectively differentiate resistance levels, with strong resistance associated with prolonged immobilization times [21]. Our findings align with this approach and support the use of a 90 min immobilization benchmark as a practical marker for phosphine resistance across species.
This study revealed variable levels of phosphine resistance across different populations of O. surinamensis, R. dominica, and C. ferrugineus, yet all three diagnostic methods (FAO, dose–response, and PTT protocols) produced consistent classifications. The novelty of this work lies in the simultaneous evaluation of these three widely used diagnostic approaches across multiple beetle species, an approach not previously applied in the context of phosphine resistance. The convergence of outcomes among protocols highlights the feasibility of establishing a standardized diagnostic framework applicable to diverse stored-product pests. Moreover, our findings emphasize that immediate immobilization following exposure could serve as a reliable early indicator of susceptibility. Future research should include a broader range of populations, particularly strongly resistant ones, and extend to field validation under commercial storage conditions to further strengthen the development of a harmonized global standard for phosphine resistance monitoring.

5. Conclusions

This study is the first to simultaneously compare the FAO protocol, the dose–response bioassay, and the Phosphine Tolerance Test across multiple beetle species. Results showed that Rhyzopertha dominica and Cryptolestes ferrugineus populations were consistently resistant, while variation was observed among Oryzaephilus surinamensis. Despite methodological differences, the three approaches produced comparable outcomes, confirming their reliability. These findings support the development of a standardized global framework for phosphine resistance monitoring and highlight the value of integrating rapid diagnostics such as the PTT into routine surveillance programs.

Author Contributions

Conceptualization, M.K.S. and C.G.A.; methodology, M.K.S.; formal analysis, M.K.S.; investigation, M.K.S. and C.G.A.; resources, C.G.A.; writing—original draft preparation, M.K.S., C.G.A. and M.-C.G.; writing—review and editing, M.K.S., C.G.A. and M.-C.G. All authors have read and agreed to the published version of the manuscript.

Funding

The research work was supported by the Project Development of Carbon Nanotube-Based Wireless Gas Sensors and Applications in Stored Product Protection and Food Safety (NANOFUM), a bilateral R&T cooperation between Greece and Germany. The study also was co-financed by the European Union and Greek national funds through the Operational Program of Competitiveness, Entrepreneurship, and Innovation, under the RESEARCH–CREATE–INNOVATE Action (project code T2EΔK-05327).

Institutional Review Board Statement

Not applicable.

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

Author Marie-Carolin Götze was employed by the company Detia Freyberg GmbH. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Table 1. List of tested species and populations, including their identification code, geographic origin, and collection date.
Table 1. List of tested species and populations, including their identification code, geographic origin, and collection date.
SpeciesPopulation CodeCountry of OriginCommodity SampledCollection Date (Month/Year)
O. surinamensisW1Germanybarley12/2016
Vis17.1Spainmaize1/2017
PesckSpainbarley10/2016
3ZolSpainbarley10/2016
Def.3.1Spainwheat + corn1/2017
Sz2Hungarybarley8/2016
LBGreece**
R. dominicaInjSerbiaflour5/2016
9CRFRomaniawheat2/2017
LBGreece**
C. ferrugineusB1Bangladeshcracked wheat6/2016
LBGreece**
* Reference susceptible populations were maintained at the LEAZ under the rearing conditions described in Section 2.
Table 2. Mean response (active, knocked-down, and immobilized adults) of O. surinamensis, R. dominica, and C. ferrugineus populations in the FAO bioassay after exposure to 30 ppm of phosphine for 20 h and subsequent evaluation 7 days later.
Table 2. Mean response (active, knocked-down, and immobilized adults) of O. surinamensis, R. dominica, and C. ferrugineus populations in the FAO bioassay after exposure to 30 ppm of phosphine for 20 h and subsequent evaluation 7 days later.
Immediate Effect (20 h)Post-Exposure Effect (7 d)Diagnosis *
PopulationsActiveKnocked-DownImmobilizedActiveKnocked-DownImmobilized
O. surinamensisW10.0 ± 0.0C1.1 ± 0.7C98.9 ± 0.7A0.0 ± 0.0C0.0 ± 0.0A100.0 ± 0.0ASusceptible
Vis17.181.5 ± 2.5B18.5 ± 2.5B0.0 ± 0.0B34.4 ± 7.6B0.6 ± 0.6A65.0 ± 8.8BResistant
Pesck0.0 ± 0.0C0.0 ± 0.0C100.0 ± 0.0A0.0 ± 0.0C0.0 ± 0.0A100.0 ± 0.0ASusceptible
3Zol0.0 ± 0.0C100.0 ± 0.0A0.0 ± 0.0B0.0 ± 0.0C0.6 ± 0.6A99.4 ± 0.5ASusceptible
Def3.1100.0 ± 0.0A0.0 ± 0.0C0.0 ± 0.0B97.8 ± 0.9A0.0 ± 0.0A2.2 ± 0.9CResistant
Sz20.0 ± 0.0C100.0 ± 0.0A0.0 ± 0.0B0.0 ± 0.0C0.0 ± 0.0A100.0 ± 0.0ASusceptible
LB0.0 ± 0.0C100.0 ± 0.0A0.0 ± 0.0B0.0 ± 0.0C0.0 ± 0.0A100.0 ± 0.0ASusceptible
R. dominicaInj86.7 ± 4.7A11.7 ± 4.6A1.6 ± 0.8A80.6 ± 7.8A12.2 ± 7.2A7.2 ± 2.6AResistant
9CRF16.1 ± 4.2B66.1 ± 6.5B17.8 ± 9.1B31.7 ± 9.8B0.0 ± 0.0B68.3 ± 9.8BResistant
LB0.0 ± 0.0C100.0 ± 0.0C0.0 ± 0.0A0.0 ± 0.0C0.0 ± 0.0B100.0 ± 0.0CSusceptible
C. ferrugineusB1100.0 ± 0.0A0.0 ± 0.0A0.0 ± 0.0A100.0 ± 0.0A0.0 ± 0.0A0.0 ± 0.0AResistant
LB0.0 ± 0.0B100.0 ± 0.0B0.0 ± 0.0A0.0 ± 0.0B0.0 ± 0.0A100.0 ± 0.0BSusceptible
Within each column and insect species, means followed by the same uppercase letter are not significantly different (in all cases df = 6.56; HSD test at 0.05). * A population was classified as resistant when active individuals were recorded at the 7 d post-exposure interval.
Table 3. Mean active, knocked-down, and immobilized adults according to the dose–response bioassay for different populations of Oryzaephilus surinamensis, Rhyzopertha dominica, and Cryptolestes ferrugineus after exposure to 50, 100, 200, 500, 700, and 1.000 ppm for 3 d and at the 7 d post-exposure time.
Table 3. Mean active, knocked-down, and immobilized adults according to the dose–response bioassay for different populations of Oryzaephilus surinamensis, Rhyzopertha dominica, and Cryptolestes ferrugineus after exposure to 50, 100, 200, 500, 700, and 1.000 ppm for 3 d and at the 7 d post-exposure time.
Concentration (ppm)
501002005007001000Diagnosis *
O. surinamensisW1Immediate effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0Susceptible
Knock-down1.1 ± 0.70.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized98.9 ± 0.7100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
Delayed effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
Vis17.1Immediate effectActive17.8 ± 6.63.3 ± 2.20.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0Weakly resistant
Knock-down45.0 ± 11.322.2 ± 7.51.1 ± 1.10.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized37.2 ± 12.274.5 ± 9.498.9 ± 1.1100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
Delayed effectActive15.6 ± 6.18.9 ± 4.90.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized84.4 ± 6.191.1 ± 4.9100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
PesckImmediate effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0Susceptible
Knock-down6.7 ± 4.495.6 ± 4.40.6 ± 0.60.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized93.3 ± 4.44.4 ± 4.499.4 ± 0.5100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
Delayed effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
3ZolImmediate effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0Susceptible
Knock-down6.1 ± 3.236.1 ± 13.90.0 ± 0.00.0 ± 0.00.6 ± 0.60.0 ± 0.0
Immobilized93.9 ± 3.263.9 ± 13.9100.0 ± 0.0100.0 ± 0.099.4 ± 0.5100.0 ± 0.0
Delayed effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
Def3.1Immediate effectActive93.9 ± 1.14.4 ± 0.50.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0Weakly resistant
Knock-down0.6 ± 0.62.8 ± 2.812.2 ± 1.51.7 ± 0.80.0 ± 0.00.0 ± 0.0
Immobilized5.5 ± 0.592.8 ± 2.987.8 ± 1.598.3 ± 0.8100.0 ± 0.0100.0 ± 0.0
Delayed effectActive29.4 ± 1.70.6 ± 0.60.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized70.6 ± 1.799.4 ± 0.5100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
Sz2Immediate effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0Susceptible
Knock-down1.1 ± 0.70.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized98.9 ± 0.7100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
Delayed effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
LBImmediate effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0Susceptible
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
Delayed effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
R. dominicaInjImmediate effectActive19.4 ± 5.16.1 ± 1.80.6 ± 0.60.0 ± 0.00.0 ± 0.00.0 ± 0.0Weakly resistant
Knock-down74.4 ± 4.019.4 ± 9.79.4 ± 0.51.1 ± 0.70.0 ± 0.00.0 ± 0.0
Immobilized6.2 ± 2.274.5 ± 9.590.0 ± 0.098.9 ± 0.7100.0 ± 0.0100.0 ± 0.0
Delayed effectActive24.4 ± 3.76.1 ± 1.47.2 ± 1.50.0 ± 0.00.0 ± 0.00.0 ± 0.0
Knock-down11.1 ± 4.40.0 ± 0.00.6 ± 0.60.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized64.5 ± 4.993.9 ± 1.492.2 ± 1.2100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
9CRFImmediate effectActive2.8 ± 1.50.0 ± 0.00.6 ± 0.60.0 ± 0.00.0 ± 0.00.0 ± 0.0Susceptible
Knock-down7.8 ± 2.21.1 ± 1.10.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized89.4 ± 3.098.9 ± 1.1100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
Delayed effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
LBImmediate effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0Susceptible
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
Delayed effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
C. ferrugineusB1Immediate effectActive100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.03.9 ± 1.63.9 ± 1.6Resistant
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.096.1 ± 1.696.1 ± 1.6
Delayed effectActive100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.03.9 ± 1.63.9 ± 1.6
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.096.1 ± 1.696.1 ± 1.6
LBImmediate effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0Susceptible
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
Delayed effectActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0
Immobilized100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0
* A population was classified as susceptible when no active individuals were recorded, weakly resistant when active individuals were recorded until 200 ppm, and resistant when active individuals were recorded after 500 ppm at the 7 d post-exposure interval.
Table 4. Results of the Probit analysis (df = 52) estimating LC50 and LC99 values for immobilized adults of Oryzaephilus surinamensis, Rhyzopertha dominica, and Cryptolestes ferrugineus after 3 d of exposure to five phosphine concentrations (50, 100, 200, 500, 700, and 1000 ppm).
Table 4. Results of the Probit analysis (df = 52) estimating LC50 and LC99 values for immobilized adults of Oryzaephilus surinamensis, Rhyzopertha dominica, and Cryptolestes ferrugineus after 3 d of exposure to five phosphine concentrations (50, 100, 200, 500, 700, and 1000 ppm).
SpeciesPopulationLC50LC99X2p
O. surinamensisW1****
O. surinamensisVis17.166.4 (48.2–80.2)195.0 (161.6–265.9)177.9<0.001
O. surinamensisPesck**177.9<0.001
O. surinamensis3Zol*503.9 *1309.4<0.001
O. surinamensisDef3.1**4365.3<0.001
O. surinamensisSz2****
O. surinamensisLB****
R. dominicaInj99.4 *297.2 *81,426.0<0.001
R. dominica9CRF****
R. dominicaLB****
C. ferrugineusB1637.6 *843.1 *14,686.9<0.001
C. ferrugineusLB****
* Could not be estimated.
Table 5. Mean numbers of active, knocked-down, and immobilized adults in the PTT for Oryzaephilus surinamensis, Rhyzopertha dominica, and Cryptolestes ferrugineus populations after exposure to 3000 ppm phosphine for intervals ranging from 5 to 270 min, followed by assessment after 7 days.
Table 5. Mean numbers of active, knocked-down, and immobilized adults in the PTT for Oryzaephilus surinamensis, Rhyzopertha dominica, and Cryptolestes ferrugineus populations after exposure to 3000 ppm phosphine for intervals ranging from 5 to 270 min, followed by assessment after 7 days.
Time (min)
SpeciesPopulation 510152025304560901201501802102402707 Days Post-ExposureDiagnosis *
O. surinamensis1WActive47.2 ± 13.00.6 ± 0.60.0 ± 0.00.0 ± 0.010.0 ± 6.60.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0 0.0 ± 0.0Susceptible
Knock-down52.8 ± 13.099.4 ± 0.6100.0 ± 0.080.6 ± 9.046.7 ± 11.47.8 ± 0.91.7 ± 0.80.6 ± 0.60.0 ± 0.0 0.0 ± 0.0
Immobilized0.0 ± 0.00.0 ± 0.00.0 ± 0.019.4 ± 9.043.3 ± 14.092.2 ± 0.998.3 ± 0.899.4 ± 0.5100.0 ± 0.0 100.0 ± 0.0
Vis17.1Active95.0 ±1.493.3 ±1.791.7 ± 0.891.1 ± 0.788.3 ± 0.885.0 ± 1.481.7 ± 2.280.0 ± 1.475.0 ± 1.448.3 ± 7.425.0 ± 2.921.7 ± 3.016.7 ± 4.216.7 ± 4.20.0 ± 0.056.1 ± 14.2Resistant
Knock-down5.0 ± 1.46.7 ± 1.78.3 ± 0.88.9 ± 0.711.7 ± 0.815.0 ± 1.418.3 ± 2.220,0± 1.425.0 ± 1.451.7 ± 7.475.0 ± 2.978.3 ± 3.083.3 ± 4.283.3 ± 4.2100.0 ± 0.016.1 ± 10.5
Immobilized0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.027.8 ± 9.3
PesckActive5.0 ± 1.70.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0 0.0 ± 0.0Susceptible
Knock-down95.0 ± 1.4100.0 ±15.5 ± 1.38.9 ± 1.17.2 ± 1.93.3 ± 1.73.3 ± 1.70.0 ± 0.00.0 ± 0.0 90.5 ± 5.5
Immobilized0.0 ± 0.00.0 ± 0.084.5 ± 1.391.1 ± 1.192.8 ± 1.996.7 ± 1.796.7 ± 1.7100.0 ± 0.0100.0 ± 0.0 9.5 ± 5.5
3ZolActive1.7 ± 1.71.7 ± 1.71.7 ± 1.74.2 ± 2.74.2 ± 2.70.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0 0.0 ± 0.0Susceptible
Knock-down98.3 ± 1.798.3 ± 1.798.3± 1.716.7 ± 5.66.7 ± 4.210.8 ± 3.73.3 ± 2.11.7 ± 1.00.0 ± 0.0 0.0 ± 0.0
Immobilized0.0 ± 0.00.0 ± 0.00.0 ± 0.079.2 ± 3.389.1 ± 3.789.2 ± 3.796.7 ± 2.198.3 ± 1.0100.0 ± 0.0 100.0 ± 0.0
Def3.1Active99.4 ± 0.698.3 ± 1.297.8 ± 1.593.9 ± 2.593.3 ± 2.392.2 ± 2.990.0 ± 2.588.9 ± 3.075.5 ± 8.155.5 ± 6.532.2 ± 8.137.2± 9.336.1 ± 9.728.3 ± 9.919.4 ± 9.983.9 ± 2.7Resistant
Knock-down0.6 ± 0.61.7 ± 1.22.2 ± 1.56.1 ± 2.56.7 ± 2.37.8 ± 2.910.0 ± 2.511.1± 3.024.5 ± 8.144.5 ± 6.557.2 ± 10.352.2 ± 10.652.8 ± 10.960.6 ± 11.969.5 ± 11.60.0 ± 0.0
Immobilized0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.010.6 ± 10.610.6 ± 10.611.1 ± 11.111.1 ± 11.111.1 ± 11.116.1 ± 2.7
Sz2Active66.7 ± 16.710.0 ± 2.95.0 ± 1.71.1 ± 0.70.6 ± 0.60.6 ± 0.60.6 ± 0.60.0 ± 0.00.0 ± 0.0 14.2 ± 1.5Resistant
Knock-down33.3 ± 16.790.0 ± 2.969.4 ± 12.268.3 ± 15.167.2 ± 16.067.2 ± 16.066.7 ± 16.366.7 ± 16.766.7 ± 16.7 0.0 ± 0.0
Immobilized0.0 ± 0.00.0 ± 0.025.6 ± 13.330.6 ± 15.332.2 ± 16.132.2 ± 16.132.7 ± 16.333.3 ± 16.733.3 ± 16.7 85.8 ± 1.5
LBActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0 0.0 ± 0.0Susceptible
Knock-down85.8 ± 5.20.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0 0.0 ± 0.0
Immobilized14.2 ± 5.2100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0 100.0 ± 0.0
R. dominicaInjActive98.9 ± 1.188.3 ± 6.575.6 ± 5.047.2 ± 6.837.2 ± 5.622.8 ± 4.84.4 ± 3.40.6 ± 0.60.0 ± 0.0 0.0 ± 0.0Susceptible
Knock-down1.1 ± 1.111.7 ± 6.524.4 ± 5.052.8 ± 6.862.8 ± 5.677.2 ± 4.895.6 ± 3.499.4 ± 0.6100.0 ± 0.0 89.4 ± 1.5
Immobilized0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0 10.6 ± 1.5
9CRFActive26.7 ± 7.35.0 ± 2.91.7 ± 1.70.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0 41.7 ± 3.3Resistant
Knock-down73.3 ± 7.395.0 ± 2.998.3 ± 1.7100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0 35.0 ± 2.9
Immobilized0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0 23.3 ± 1.7
LBActive1.7 ± 1.70.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0 0.0 ± 0.0Susceptible
Knock-down98.3 ± 1.7100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0 0.0 ± 0.0
Immobilized0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0 100.0 ± 0.0
C. ferrugineusB1Active100.0 ± 0.0100.0 ± 0.0100.0 ± 0.096.7 ± 0.096.7 ± 0.096.7 ± 0.096.7 ± 0.096.7 ± 0.096.7 ± 0.0 83.3 ± 3.3Resistant
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.03.3 ± 1.73.3 ± 1.73.3 ± 1.73.3 ± 1.73.3 ± 1.7 0.0 ± 0.0
Immobilized0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0 16.7 ± 3.3
LBActive0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0 0.0 ± 0.0Susceptible
Knock-down0.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.00.0 ± 0.0 0.0 ± 0.0
Immobilized100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0100.0 ± 0.0 100.0 ± 0.0
* Populations were considered resistant if active adults were still observed at the 7 d evaluation following exposure.
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Sakka, M.K.; Götze, M.-C.; Athanassiou, C.G. Phosphine Susceptibility Screening of Three Different Stored Product Beetle Species by Using Three Diagnostic Techniques. Agriculture 2025, 15, 1904. https://doi.org/10.3390/agriculture15171904

AMA Style

Sakka MK, Götze M-C, Athanassiou CG. Phosphine Susceptibility Screening of Three Different Stored Product Beetle Species by Using Three Diagnostic Techniques. Agriculture. 2025; 15(17):1904. https://doi.org/10.3390/agriculture15171904

Chicago/Turabian Style

Sakka, Maria K., Marie-Carolin Götze, and Christos G. Athanassiou. 2025. "Phosphine Susceptibility Screening of Three Different Stored Product Beetle Species by Using Three Diagnostic Techniques" Agriculture 15, no. 17: 1904. https://doi.org/10.3390/agriculture15171904

APA Style

Sakka, M. K., Götze, M.-C., & Athanassiou, C. G. (2025). Phosphine Susceptibility Screening of Three Different Stored Product Beetle Species by Using Three Diagnostic Techniques. Agriculture, 15(17), 1904. https://doi.org/10.3390/agriculture15171904

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