A rapid method to detect Cryptolestes ferrugineus (Coleoptera: Cucujidae) larvae in stored grain

Abstract

. 2002. A rapid method to detect Cryptolestes ferrugineus (Coleoptera: Cucujidae) larvae in stored grain. Can. J. Plant Sci. 82: 591-597. Modifications of three detection methods, based on the heat-gradient principle employed by the Berlese funnel method were investigated to extract larvae of the rusty grain beetle, Cryptolestes ferrugineus (Stephens), developing under the seed coats of infested kernels in grain samples. Onekilogram samples of wheat, barley and corn were artificially infested with rusty grain beetle eggs, resulting in survival rates (to larval stage) of 71.1 ± 14.4, 58.9 ± 14.3, and 24.7 ± 11.8%, respectively. Sets of 10 infested kernels containing different-aged larvae (10 individuals ¥ 4 instars) were added to 1-kg samples of hydrated grain, then heated on screens beneath heat sources (lights) at several heights in three different containers (Berlese funnel, with a 7-cm-deep grain layer, or square and rectangular screened boxes with a grain layer several kernels deep). There were no significantly different extraction rates between the rectangular and square containers for all heating trials. A larval extraction rate of 31% was produced by 1-h trials with wheat (15% moisture content wet basis) 5.5 cm below the lamp bank with a thermostat set at 50°C. This matched the efficiency of the Berlese funnel method (36% extraction in 6 h), but in much less time. Similar results were found for barley, but for corn the square and rectangle gave significantly better extraction than the Berlese funnel, although extraction efficiency was half that of wheat and barley. Considerably lower extraction rates were obtained from trials that did not use a thermostat. The results from this experiment show that there is a potential alternative detection method with the thermostatically controlled heating of a thin layer of grain that should be faster than the conventional 6-h Berlese funnel method. Cette méthode s'avère aussi efficace que l'appareil de Berlèse (taux d'extraction de 36 % au bout de 6 heures), mais est beaucoup plus rapide. Des résultats analogues ont été obtenus avec l'orge, mais les récipients carré et rectangulaire donnent un taux d'extraction significativement supérieur à celui de l'appareil de Berlèse pour le maïs, même si l'extraction est deux fois moins efficace qu'avec l'orge ou le blé. Sans thermostat, les essais entraînent un taux d'extraction considérablement plus faible. Les résultats indiquent que le chauffage d'une mince couche de grains avec réglage thermostatique pourrait constituer une méthode de dépistage plus rapide que la technique traditionnelle avec l'appareil de Berlèse.

A new method to rapidly detect rusty grain beetle, Cryptolestes ferrugineus (Stephens), in stored grain

“…This explains why both old and young larvae were extracted by microwave method with no significant difference (Table 1). This study found the Berlese funnel method could recover more old larvae than young larvae, which is inconsistent with the report by Minkevich et al (2002). This contradiction might be caused by different setups such as the distances between lamp and grain surface and depths of grain inside Berlese funnels.…”

“…This result indicated that the heat produced by either the microwaves or incandescent light bulb was the same on the effectiveness of forcing larvae out of grain kernels (Smith, 1977;Minkevich et al, 2002;Jian et al, 2014a). The higher recovery percentage associated with the microwave treatment was caused by the shaking and mixing during microwave treatment after larvae escaped out of grain kernels.…”

“…This contradiction might be caused by different setups such as the distances between lamp and grain surface and depths of grain inside Berlese funnels. The distance and depth influence extraction percentage (Minkevich et al, 2002) because young larvae might have a lower ability to move through the grain mass inside the Berlese funnels before they are killed by heat produced by the incandescent light bulb.…”

“…The Berlese funnel method uses an incandescent light bulb to provide heat that forces insects to exit the grain kernels and the grain mass into a collection jar (Berlese, 1905). Problems with this method are: it takes at least 6 h, collects only 30e70% of insects in the grain samples (Minkevich et al, 2002), uses incandescent light bulbs which are being phased-out, and requires extensive space for running multiple samples. Thin-or multi-layers are suggested to increase the rapidity of this method (Demianyk et al, 1997;Minkevich et al, 2002).…”

“…Problems with this method are: it takes at least 6 h, collects only 30e70% of insects in the grain samples (Minkevich et al, 2002), uses incandescent light bulbs which are being phased-out, and requires extensive space for running multiple samples. Thin-or multi-layers are suggested to increase the rapidity of this method (Demianyk et al, 1997;Minkevich et al, 2002). However, these modified methods did not increase the detection accuracy.…”