<abstract xmlns="http://www.w3.org/1999/xhtml">

<p><italic>Megaselia scalaris</italic> (Loew) (Diptera: Phoridae) is a synanthropic fly that lives in a wide range of warmer regions globally. Although it is listed as a quarantine pest in the Eurasian Economic Union, phytosanitary protocols have not been established. The larva feeds on moist food material and cannot grow on dry matter, including cured tobacco. However, adults of this species have been detected in containers containing tobacco in Russian ports. In this study, difference in susceptibility to phosphine between developmental stages and the lethal effect of phosphine on adults was evaluated. Fortunately, the adult which is the potential contaminable stage in tobacco was demonstrated to be the least tolerant. The phosphine concentrations to achieve probit 9 mortality (≈LC<sub>99.9968</sub>) for adult flies were calculated to be 636.2 ppm at 15 °C, 565.9 ppm at 20 °C, and 280.1 ppm at 25 °C with 6 h of exposure. The concentration × time products (<italic>Ct</italic>, ppm·d), the cumulative exposure to the fumigant, at respective temperatures were calculated as 159.1 ppm·d at 15 °C, 141.5 ppm·d at 20 °C, and 70.0 ppm·d at 25 °C, which are much lower than those recommended for the control of insect pests of cured tobacco leaves by CORESTA (Cooperation Centre for Scientific Research Relative to Tobacco). These are 1800 ppm·d (300 ppm × 6 d) at 16–20 °C and 800 ppm·d (200 ppm × 4 d) at temperatures higher than 20 °C. The results suggest that the standard fumigation protocol for stored tobacco will be adequate to control adult <italic>M. scalaris</italic>. The probit 9 values obtained in this study can be further utilized for the development of phosphine-based quarantine and preshipment treatments for this species.</p>
</abstract>

Megaselia scalaris (Loew) (Diptera: Phoridae) is a synanthropic fly that lives in a wide range of warmer regions globally. Although it is listed as a quarantine pest in the Eurasian Economic Union, phytosanitary protocols have not been established. The larva feeds on moist food material and cannot grow on dry matter, including cured tobacco. However, adults of this species have been detected in containers containing tobacco in Russian ports. In this study, difference in susceptibility to phosphine between developmental stages and the lethal effect of phosphine on adults was evaluated. Fortunately, the adult which is the potential contaminable stage in tobacco was demonstrated to be the least tolerant. The phosphine concentrations to achieve probit 9 mortality (≈LC99.9968) for adult flies were calculated to be 636.2 ppm at 15 °C, 565.9 ppm at 20 °C, and 280.1 ppm at 25 °C with 6 h of exposure. The concentration × time products (Ct, ppm·d), the cumulative exposure to the fumigant, at respective temperatures were calculated as 159.1 ppm·d at 15 °C, 141.5 ppm·d at 20 °C, and 70.0 ppm·d at 25 °C, which are much lower than those recommended for the control of insect pests of cured tobacco leaves by CORESTA (Cooperation Centre for Scientific Research Relative to Tobacco). These are 1800 ppm·d (300 ppm × 6 d) at 16–20 °C and 800 ppm·d (200 ppm × 4 d) at temperatures higher than 20 °C. The results suggest that the standard fumigation protocol for stored tobacco will be adequate to control adult M. scalaris. The probit 9 values obtained in this study can be further utilized for the development of phosphine-based quarantine and preshipment treatments for this species.


<div xmlns="http://www.w3.org/1999/xhtml">
<sec id="j_cttr-2022-0010_s_001"><div>INTRODUCTION</div>
<p><italic>Megaselia scalaris</italic> (Loew) (Diptera: Phoridae) is a cosmopolitan and synanthropic fly mainly found near areas inhabited by humans in warm climate regions (<a ref-type="bibr" href="#j_cttr-2022-0010_ref_001">1</a>). It is essentially a detritivore species feeding on a variety of foods of both animal and plant origins, regardless of whether they are fresh or decaying (<a ref-type="bibr" href="#j_cttr-2022-0010_ref_002">2</a>). These diverse feeding habits make this species a facultative predator, parasite, and parasitoid of invertebrates and vertebrates (<a ref-type="bibr" href="#j_cttr-2022-0010_ref_002">2</a>, <a ref-type="bibr" href="#j_cttr-2022-0010_ref_003">3</a>) and it is classified as a quarantine pest in the Eurasian Economic Union (<a ref-type="bibr" href="#j_cttr-2022-0010_ref_004">4</a>). Effective disinfestation methods of this insect have not been developed because it is not regarded as an agricultural/veterinary pest in the other countries. Recently, R<sc>osselkhoznadzor</sc> (Federal Service for Veterinary and Phytosanitary Surveillance of Russia) announced that this quarantine species was found in imported containers with raw tobacco from various countries in Africa, South and North America, Europe, and Asia, and the phytosanitary regulation of tobacco has been enhanced (<a ref-type="bibr" href="#j_cttr-2022-0010_ref_005">5</a>, <a ref-type="bibr" href="#j_cttr-2022-0010_ref_006">6</a>). The larvae of this species depend on moist decaying and relatively fluid plant or animal matter suitable for their sponging mouthparts, and females lay eggs on decomposing material that has become a fluid, allowing larvae to feed as soon as they hatch (<a ref-type="bibr" href="#j_cttr-2022-0010_ref_007">7</a>). Therefore, cured tobacco is not infested by this species, and the adults intercepted in Russian ports must have been hitchhikers during marine transportation.</p>
<p>In the tobacco industry, phosphine has been the most widely used insecticide to control of common insect pests associated with cured tobaccos such as the cigarette beetle, <italic>Lasioderma serricorne</italic> (Coleoptera: Ptinidae) and the tobacco moth <italic>Ephestia elutella</italic> (Lepidoptera: Pyralidae) (<a ref-type="bibr" href="#j_cttr-2022-0010_ref_008">8</a>). There are no data on the efficacy of phosphine against <italic>M. scalaris</italic>. At first, we exposed eggs, larvae, pupae and adults to 200 ppm phosphine to determine relative susceptibility to phosphine in developmental stages. A phytosanitary treatment should be effective against the most tolerant stage that may be present in a traded commodity (<a ref-type="bibr" href="#j_cttr-2022-0010_ref_009">9</a>). Because life stages other than adults are not associated with cured tobacco, the following study was conducted to examine the effects of phosphine on adult flies and to estimate the dose required for a phytosanitary treatment for this species.</p>
</sec>
<sec id="j_cttr-2022-0010_s_002"><div>MATERIALS AND METHODS</div>
<sec id="j_cttr-2022-0010_s_002_s_001"><div>Test insects</div>
<p><italic>Megaselia scalaris</italic> was originally purchased from Sumika Technoservice Corp. (Hyogo, Japan) and maintained on a 1:1:2 mixture of rodent diet (Oriental Yeast Co. Ltd., Tokyo, Japan), wheat bran, and water (<a ref-type="bibr" href="#j_cttr-2022-0010_ref_010">10</a>), under 24–28 °C. Twenty unsexed adults (2–3 d after emergence) were released on 4 g of feed in 29 mm ∅ × 95 mm polystyrene vials, and the vials were capped with a polyurethane foam plug. After 24–48 h, the adults were removed, and another 48–72 h later, ca. 1 g of wheat bran was used in the diet for pupation. The pupae were collected from the bran and maintained under rearing conditions. The adults were collected within 24 h of emergence and fed a 10% glucose solution.</p>
</sec>
<sec id="j_cttr-2022-0010_s_002_s_002"><div>Fumigation procedure</div>
<p>The third instar larvae and pupae for the evaluation of phosphine susceptibility were collected from rearing vials. Adults within 24 h after emergence were collected after being kept at 5 °C for 5–10 min to suppress their moving. To prepare eggs, 30 unsexed adults of 48–72 h after emergence were enclosed in 25 mm ∅ × 50 mm vials and covered with #80 nylon mesh. A piece of absorbent cotton soaked in 1% solution of beef extract (Nacalai Tesque, Kyoto, Japan) was put on the mesh cover, and the vial was kept at 27 °C for 12–14 h under darkness. The deposited eggs on the mesh and cotton were picked up with a fine brush. Fifty eggs, 30 larvae, 30 pupae, or 30 adults were placed as a group into polystyrene vials measuring 29 mm in diameter and 95 mm long with 1 g feed. The vials were then placed in gas-tight acrylic resin container measuring 160 mm × 295 mm × 100 mm. Three vials for each developmental stage were used in the experiment. Phosphine fumigation was performed using the protocols described by HORI and KASAISHI (<a ref-type="bibr" href="#j_cttr-2022-0010_ref_011">11</a>). Phosphine was generated from aluminum phosphide (Tyvek<sup>®</sup>, Degesch Japan Co. Ltd., Saitama, Japan) and introduced into the containers after adjusting the concentrations using a phosphine gas analyser (Komyo Rikagaku Kogyo K.K., Kanagawa, Japan).</p>
<p>To assess the susceptibility of developmental stages, the containers with 200 ppm phosphine were maintained at 25 °C for either of 2, 4, 8, or 24 h in an MLR-352 plant growth chamber (PHC Corporation, Tokyo, Japan). For untreated control, the container prepared in the same manner without phosphine were kept at 25 °C for 24 h. For dose-response assay, the containers with/without phosphine were maintained at either of 15, 20, or 25 °C for 6 h. After exposure, the insects in vials were held at 27 °C until their survival was checked. Life or death of adults was determined 1–2 h after treatments and those of the other stages were determined 14 d after treatments.</p>
</sec>
<sec id="j_cttr-2022-0010_s_002_s_003"><div>Data analysis</div>
<p>Probit analysis was performed using the PriProbit (ver. 1.63) computer program developed by SAKUMA (<a ref-type="bibr" href="#j_cttr-2022-0010_ref_012">12</a>) which was downloaded from <ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.ars.usda.gov/Services/docs.htm?docid=11284">http://www.ars.usda.gov/Services/docs.htm?docid=11284</ext-link>. The phosphine concentrations needed to achieve probit 9 mortality (≈LC<sub>99.9968</sub>) were read from the data table for linear graphic display.</p>
</sec>
</sec>
<sec id="j_cttr-2022-0010_s_003"><div>RESULTS AND DISCUSSION</div>
<sec id="j_cttr-2022-0010_s_003_s_001"><div>Relative susceptibility to phosphine in developmental stages</div>
<p><a ref-type="table" href="#j_cttr-2022-0010_tab_001">Table 1</a> shows the lethality of phosphine to each developmental stage. All adults exposed to 200 ppm phosphine at 25 °C died within 4 h, and the most pupae survived the same treatment for 24 h exposure. These results show that the pupa is the most tolerant and that the adult is the most susceptible stage to phosphine. Fortunately, life stages other than adults are not associated with cured tobacco, and therefore a phytosanitary treatment should be effective against adult, the least tolerant stage.</p>
<table-wrap id="j_cttr-2022-0010_tab_001" position="float"><label>Table 1</label><caption><p>Phosphine susceptibility of developmental stages of Megaselia scalaris (200 ppm, 25 °C).</p></caption>
<table frame="hsides" rules="groups">
<thead>
<tr>
<th align="center" valign="middle" rowspan="3">Stage</th>
<th align="center" valign="middle" rowspan="3">Number of insects</th>
<th align="center" valign="middle" colspan="5">Mortality (%)<hr/></th>
</tr>
<tr>
<th align="center" valign="middle" colspan="5">Exposure time (h)<hr/></th>
</tr>
<tr>
<th align="center" valign="middle">0 (control)</th>
<th align="center" valign="middle">2</th>
<th align="center" valign="middle">4</th>
<th align="center" valign="middle">8</th>
<th align="center" valign="middle">24</th>
</tr>
</thead>
<tbody>
<tr>
<td align="left" valign="top">Egg</td>
<td align="center" valign="top">150</td>
<td align="center" valign="top">2.0</td>
<td align="center" valign="top">4.0</td>
<td align="center" valign="top">18.0</td>
<td align="center" valign="top">84.7</td>
<td align="center" valign="top">100</td>
</tr>
<tr>
<td align="left" valign="top">Larva</td>
<td align="center" valign="top">90</td>
<td align="center" valign="top">0.0</td>
<td align="center" valign="top">4.4</td>
<td align="center" valign="top">20.0</td>
<td align="center" valign="top">71.1</td>
<td align="center" valign="top">100</td>
</tr>
<tr>
<td align="left" valign="top">Pupa</td>
<td align="center" valign="top">90</td>
<td align="center" valign="top">4.4</td>
<td align="center" valign="top">1.1</td>
<td align="center" valign="top">7.8</td>
<td align="center" valign="top">13.3</td>
<td align="center" valign="top">15.6</td>
</tr>
<tr>
<td align="left" valign="top">Adult</td>
<td align="center" valign="top">90</td>
<td align="center" valign="top">0.0</td>
<td align="center" valign="top">75.6</td>
<td align="center" valign="top">100</td>
<td align="center" valign="top">100</td>
<td align="center" valign="top">100</td>
</tr>
</tbody>
</table>
</table-wrap>
</sec>
<sec id="j_cttr-2022-0010_s_003_s_002"><div>Probit 9 mortality of adult</div>
<p>No adult flies died that were not treated with phosphine. The mortality data obtained in this test were well fitted with the probit model (<a ref-type="fig" href="#j_cttr-2022-0010_fig_001">Figure 1</a>). The phosphine concentrations required to achieve probit 9 mortalities (≈LC<sub>99.9968</sub>) in the adult were calculated to be 636.2 ppm at 15 °C, 565.9 ppm at 20 °C, and 280.1 ppm at 25 °C (<a ref-type="table" href="#j_cttr-2022-0010_tab_002">Table 2</a>). The concentration × time products (<italic>Ct</italic>, ppm·d) at the respective temperatures were calculated to be 159.1 ppm·d at 15 °C, 141.5 ppm·d at 20 °C, and 70.0 ppm·d at 25 °C. These values are lower than those recommended for the control of insect pests of cured tobacco leaves by CORESTA, which are 1800 ppm·d (300 ppm × 6 d) at 16–20 °C and 800 ppm·d (200 ppm × 4 d) at temperatures higher than 20 °C (<a ref-type="bibr" href="#j_cttr-2022-0010_ref_008">8</a>). Phosphine is much more effective at lower concentrations over longer exposure periods than at higher concentrations for a shorter period; the relationship can be expressed by the modified form <italic>C<sup>n</sup>t = k</italic> (constant), where <italic>n</italic> is less than 1 (<a ref-type="bibr" href="#j_cttr-2022-0010_ref_013">13</a>). Such a relationship has not been confirmed in this species. However, it appears that the CORESTA recommendations for cured tobacco fumigation will also control the adults of <italic>M. scalaris</italic>.</p>
<figure id="j_cttr-2022-0010_fig_001" position="float" fig-type="figure"><h2>Figure 1</h2><figCaption><p><bold>Probit mortality of adult <italic>Megaselia scalaris</italic> in relation to phosphine concentration with 6 h exposure at three different temperatures</bold>. Filled circles, cross marks, and open circles represent mortality at 15 °C, 20 °C, and 25 °C, respectively.</p></figCaption><img xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/j_cttr-2022-0010_fig_001.jpg" src="https://sciendo-parsed.s3.eu-central-1.amazonaws.com/6471adb8215d2f6c89dacc3d/j_cttr-2022-0010_fig_001.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Date=20240703T162156Z&amp;X-Amz-SignedHeaders=host&amp;X-Amz-Expires=18000&amp;X-Amz-Credential=AKIA6AP2G7AKP25APDM2%2F20240703%2Feu-central-1%2Fs3%2Faws4_request&amp;X-Amz-Signature=4e40ece4b2c91af323d7df99c31478ed879bd211cbf034d9b9ed5aed0b77e45a" class="mw-100"/></figure>
<table-wrap id="j_cttr-2022-0010_tab_002" position="float"><label>Table 2</label><caption><p>Phosphine concentrations (ppm) required to achieve 99% (LC<sub>99</sub>) and 99.9968% (LC<sub>99.9968</sub> Probit 9) mortalities of adult Megaselia scalaris with 6 h exposure.</p></caption>
<table frame="hsides" rules="groups">
<thead>
<tr>
<th align="left" valign="middle">Temperature</th>
<th align="center" valign="middle">Number of insects</th>
<th align="center" valign="middle">Slope ± SE</th>
<th align="center" valign="middle">Intercept ± SE</th>
<th align="center" valign="middle">LC<sub>99</sub> (95% Fiducial limits), ppm</th>
<th align="center" valign="middle">LC<sub>99.9968</sub> (95% Fiducial limits), ppm</th>
</tr>
</thead>
<tbody>
<tr>
<td align="left" valign="top">15 °C</td>
<td align="center" valign="top">1350</td>
<td align="center" valign="top">4.394 ± 0.334</td>
<td align="center" valign="top">−8.319 ± 0.658</td>
<td align="center" valign="top">264.6 (223.9 – 332.0)</td>
<td align="center" valign="top">636.2 (478.5 – 942.9)</td>
</tr>
<tr>
<td align="left" valign="top">20 °C</td>
<td align="center" valign="top">1260</td>
<td align="center" valign="top">4.081 ± 0.383</td>
<td align="center" valign="top">−7.234 ± 0.703</td>
<td align="center" valign="top">22.0 (176.4 – 305.2)</td>
<td align="center" valign="top">565.9 (388.5 – 996.6)</td>
</tr>
<tr>
<td align="left" valign="top">25 °C</td>
<td align="center" valign="top">1440</td>
<td align="center" valign="top">4.208 ± 0.269</td>
<td align="center" valign="top">−6.298 ± 0.430</td>
<td align="center" valign="top">112.0 (96.9 – 135.0)</td>
<td align="center" valign="top">280.1 (218.3 – 387.3)</td>
</tr>
</tbody>
</table>
</table-wrap>
<p>Large-scale confirmatory tests should be further performed to validate the efficacy for quarantine treatment. Theoretically, a minimum of 93,613 insects are required to verify the probit standard at the 95% confidence level (<a ref-type="bibr" href="#j_cttr-2022-0010_ref_014">14</a>). The estimated probit 9 values obtained in this study can be utilized for the development of phosphine-based quarantine and preshipment treatments for this species.</p>
</sec>
</sec>
</div>

Phosphine Susceptibility of Adult <italic>Megaselia scalaris</italic> (Loew) (Diptera: Phoridae)

<trans-abstract xml:lang="de" xmlns="http://www.w3.org/1999/xhtml">

<p>Bei <italic>Megaselia scalaris</italic> (Loew) (Diptera: Phoridae) handelt es sich um eine synanthrope Fliege, die in den wärmeren Weltregionen weit verbreitet ist. Obwohl sie in der Eurasischen Wirtschaftsunion auf der Liste der Quarantäneschädlinge geführt wird, existieren für sie bisher keine Pflanzenschutzprotokolle. Die Larve ernährt sich von feuchter Nahrung und gedeiht nicht auf Trockensubstanz wie z.B. getrocknetem Tabak. In russischen Häfen sind allerdings erwachsene Exemplare dieser Fliegenart in Containern mit Tabak entdeckt worden. In der vorliegenden Studie werden Unterschiede in der Empfindlichkeit gegenüber Phosphin bei verschiedenen Entwicklungsstadien sowie die letale Wirkung von Phosphin bei adulten Tieren untersucht. Glücklicherweise erweist sich die erwachsene Fliege, die bei Tabak ein potenzielles Kontaminationsrisiko darstellt, als am wenigsten tolerant gegenüber Phosphin. Für adulte Fliegen wurden die Phosphinkonzentrationen zum Erreichen einer Mortalität von Probit 9 (≈LC<sub>99.9968</sub>) bei einer Expositionsdauer von 6 Stunden wie folgt berechnet: 636,2 ppm bei 15 °C, 565,9 ppm bei 20 °C und 280,1 ppm bei 25° C. Bei der Berechnung der Produkte aus Konzen-tration × Zeit (<italic>Ct</italic>, ppm·d), d.h. der kumulativen Exposition gegenüber dem Begasungsmittel, erhält man für die verschiedenen Temperaturen jeweils folgende Werte: 159,1 ppm·d bei 15 °C, 141,5 ppm·d bei 20 °C und 70,0 ppm·d bei 25 °C. Diese sind deutlich niedriger als die von CORESTA (Cooperation Centre for Scientific Research Relative to Tobacco) für getrocknete Tabakblätter zur Bekämpfung von Schadinsekten empfohlenen Werte von 1800 ppm·d (300 ppm × 6 d) bei 16 °C bis 20 °C und 800 ppm·d (200 ppm × 4 d) bei Temperaturen über 20 °C. Die Ergebnisse deuten darauf hin, dass das Standardprotokoll zur Begasung von gelagertem Tabak für die Kontrolle der adulten <italic>M. scalaris</italic> hinreichend ist. Die in dieser Studie ermittelten Probit-9-Werte können für die Entwicklung von Quarantäne- und Vorversandbehandlungen auf Phosphinbasis für diese Fliegenart weiterverwendet werden.</p>
</trans-abstract>

Bei Megaselia scalaris (Loew) (Diptera: Phoridae) handelt es sich um eine synanthrope Fliege, die in den wärmeren Weltregionen weit verbreitet ist. Obwohl sie in der Eurasischen Wirtschaftsunion auf der Liste der Quarantäneschädlinge geführt wird, existieren für sie bisher keine Pflanzenschutzprotokolle. Die Larve ernährt sich von feuchter Nahrung und gedeiht nicht auf Trockensubstanz wie z.B. getrocknetem Tabak. In russischen Häfen sind allerdings erwachsene Exemplare dieser Fliegenart in Containern mit Tabak entdeckt worden. In der vorliegenden Studie werden Unterschiede in der Empfindlichkeit gegenüber Phosphin bei verschiedenen Entwicklungsstadien sowie die letale Wirkung von Phosphin bei adulten Tieren untersucht. Glücklicherweise erweist sich die erwachsene Fliege, die bei Tabak ein potenzielles Kontaminationsrisiko darstellt, als am wenigsten tolerant gegenüber Phosphin. Für adulte Fliegen wurden die Phosphinkonzentrationen zum Erreichen einer Mortalität von Probit 9 (≈LC99.9968) bei einer Expositionsdauer von 6 Stunden wie folgt berechnet: 636,2 ppm bei 15 °C, 565,9 ppm bei 20 °C und 280,1 ppm bei 25° C. Bei der Berechnung der Produkte aus Konzen-tration × Zeit (Ct, ppm·d), d.h. der kumulativen Exposition gegenüber dem Begasungsmittel, erhält man für die verschiedenen Temperaturen jeweils folgende Werte: 159,1 ppm·d bei 15 °C, 141,5 ppm·d bei 20 °C und 70,0 ppm·d bei 25 °C. Diese sind deutlich niedriger als die von CORESTA (Cooperation Centre for Scientific Research Relative to Tobacco) für getrocknete Tabakblätter zur Bekämpfung von Schadinsekten empfohlenen Werte von 1800 ppm·d (300 ppm × 6 d) bei 16 °C bis 20 °C und 800 ppm·d (200 ppm × 4 d) bei Temperaturen über 20 °C. Die Ergebnisse deuten darauf hin, dass das Standardprotokoll zur Begasung von gelagertem Tabak für die Kontrolle der adulten M. scalaris hinreichend ist. Die in dieser Studie ermittelten Probit-9-Werte können für die Entwicklung von Quarantäne- und Vorversandbehandlungen auf Phosphinbasis für diese Fliegenart weiterverwendet werden.

<trans-abstract xml:lang="fr" xmlns="http://www.w3.org/1999/xhtml">

<p>La <italic>Megaselia scalaris</italic> (Loew) (Diptera: Phoridae) est une mouche synanthrope largement présente dans les régions plus chaudes de la planète. Bien qu’elle figure sur la liste des organismes de quarantaine de l’Union économique eurasiatique, aucun protocole phytosanitaire n’a, à ce jour, été établi pour cette espèce. Les larves se nourrissent de matières alimentaires humides et ne peuvent se développer sur des matières sèches, en ce compris le tabac séché. Toutefois, des spécimens adultes de cette espèce ont été détectés, dans des ports russes, à l’intérieur de conteneurs transportant du tabac. La présente étude évalue la différence de susceptibilité à la phosphine selon les stades de développement ainsi que l’effet létal de la phosphine sur les individus adultes. Par chance, l’étude prouve que l’adulte présentant potentiellement un danger de contamination du tabac s’avère être le moins tolérant à la phosphine. Les concentrations de phosphine nécessaires pour assurer une mortalité de probit 9 (≈LC<sub>99.9968</sub>) chez les adultes furent établies, selon nos calculs, à 636,2 ppm à 15 °C, 565,9 ppm à 20 °C et 280,1 ppm à 25° C pour un temps d’exposition de 6 h. Le calcul des produits de la concentration × temps (<italic>Ct</italic>, ppm·d), soit l’exposition cumulative au fumigant pour chaque température respective donna les résultats suivants: 159,1 ppm·d à 15 °C, 141,5 ppm·d à 20 °C et 70,0 ppm·d à 25 °C, soit des valeurs inférieures à celles préconisées, par le CORESTA (Centre de coopération pour les recherches scientifiques relatives au tabac), pour le contrôle des insectes nuisibles des feuilles de tabac séché, à savoir 1800 ppm·d (300 ppm × 6 d) à une température oscillant entre 16 et 20 °C et 800 ppm·d (200 ppm × 4 d) à des températures supérieures à 20°C. Les résultats laissent à penser que le protocole normalisé de fumigation du tabac entreposé conviendra pour le contrôle des spécimens adultes de la <italic>M. scalaris</italic>. Les valeurs de probit 9 obtenues dans la présente étude pourront être ultérieurement utilisées pour la mise au point d’un traitement à base de phosphine pour cette espèce avant expédition et durant la quarantaine.</p>
</trans-abstract>

La Megaselia scalaris (Loew) (Diptera: Phoridae) est une mouche synanthrope largement présente dans les régions plus chaudes de la planète. Bien qu’elle figure sur la liste des organismes de quarantaine de l’Union économique eurasiatique, aucun protocole phytosanitaire n’a, à ce jour, été établi pour cette espèce. Les larves se nourrissent de matières alimentaires humides et ne peuvent se développer sur des matières sèches, en ce compris le tabac séché. Toutefois, des spécimens adultes de cette espèce ont été détectés, dans des ports russes, à l’intérieur de conteneurs transportant du tabac. La présente étude évalue la différence de susceptibilité à la phosphine selon les stades de développement ainsi que l’effet létal de la phosphine sur les individus adultes. Par chance, l’étude prouve que l’adulte présentant potentiellement un danger de contamination du tabac s’avère être le moins tolérant à la phosphine. Les concentrations de phosphine nécessaires pour assurer une mortalité de probit 9 (≈LC99.9968) chez les adultes furent établies, selon nos calculs, à 636,2 ppm à 15 °C, 565,9 ppm à 20 °C et 280,1 ppm à 25° C pour un temps d’exposition de 6 h. Le calcul des produits de la concentration × temps (Ct, ppm·d), soit l’exposition cumulative au fumigant pour chaque température respective donna les résultats suivants: 159,1 ppm·d à 15 °C, 141,5 ppm·d à 20 °C et 70,0 ppm·d à 25 °C, soit des valeurs inférieures à celles préconisées, par le CORESTA (Centre de coopération pour les recherches scientifiques relatives au tabac), pour le contrôle des insectes nuisibles des feuilles de tabac séché, à savoir 1800 ppm·d (300 ppm × 6 d) à une température oscillant entre 16 et 20 °C et 800 ppm·d (200 ppm × 4 d) à des températures supérieures à 20°C. Les résultats laissent à penser que le protocole normalisé de fumigation du tabac entreposé conviendra pour le contrôle des spécimens adultes de la M. scalaris. Les valeurs de probit 9 obtenues dans la présente étude pourront être ultérieurement utilisées pour la mise au point d’un traitement à base de phosphine pour cette espèce avant expédition et durant la quarantaine.

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Phosphine Susceptibility of Adult  (Loew) (Diptera: Phoridae)

Megaselia scalaris (Loew) (Diptera: Phoridae) is a synanthropic fly that lives in a wide range of warmer regions globally. Although it is listed as a...

Phosphine Susceptibility of Adult Megaselia scalaris (Loew) (Diptera: Phoridae)

Online veröffentlicht: 15. Aug. 2022

Seitenbereich: 101 - 105

Eingereicht: 03. Okt. 2021

Akzeptiert: 14. Apr. 2022

DOI: https://doi.org/10.2478/cttr-2022-0010

© 2022 Hirohide Iwamoto et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Figure 1

Phosphine concentrations (ppm) required to achieve 99% (LC99) and 99.9968% (LC99.9968 Probit 9) mortalities of adult Megaselia scalaris with 6 h exposure.

Phosphine susceptibility of developmental stages of Megaselia scalaris (200 ppm, 25 °C).

Temperature	Number of insects	Slope ± SE	Intercept ± SE	LC₉₉ (95% Fiducial limits), ppm	LC_99.9968 (95% Fiducial limits), ppm
15 °C	1350	4.394 ± 0.334	−8.319 ± 0.658	264.6 (223.9 – 332.0)	636.2 (478.5 – 942.9)
20 °C	1260	4.081 ± 0.383	−7.234 ± 0.703	22.0 (176.4 – 305.2)	565.9 (388.5 – 996.6)
25 °C	1440	4.208 ± 0.269	−6.298 ± 0.430	112.0 (96.9 – 135.0)	280.1 (218.3 – 387.3)

Stage	Number of insects	Mortality (%)
		Exposure time (h)
		0 (control)	2	4	8	24
Egg	150	2.0	4.0	18.0	84.7	100
Larva	90	0.0	4.4	20.0	71.1	100
Pupa	90	4.4	1.1	7.8	13.3	15.6
Adult	90	0.0	75.6	100	100	100