Abstract
Simple SummaryThe sawtoothed grain beetle, the red flour beetle and the rice weevil are three major stored product insects that attack different stored products worldwide. Limited chemical options are available, and eco-friendlier management strategies are needed. Low oxygen treatment can be used as an alternative method to limit chemical treatments. Therefore, we conducted nine trials in commercial nitrogen chambers with phosphine susceptible and resistant populations. The vials with insects were placed in different locations inside the chambers and mortality was recorded after the termination of each trial. The vials were kept at laboratory conditions for 65 days in order to measure progeny production. Low or no survival was recorded in all cases for all species. Moreover, progeny production was suppressed with some exceptions for some species and populations. The current study indicates that low oxygen is effective against phosphine susceptible and resistant populations and can be used as alternative method to chemicals.In this study, we evaluated nitrogen treatment on phosphine-resistant field and -susceptible laboratory populations of different stored product beetles. Nine trials were conducted in commercial nitrogen chambers with the O2 level set at 1.0%. Two different temperatures—i.e., 28 and 40 °C—and three exposure intervals—i.e., 2.5, 3 and 9 d—were used in our tests. Adults of the sawtoothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae); the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae); and the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) were used in the trials. The insects were placed in vials with different commodities per species and population, and their mortality was measured after the termination of each trial. Then, the vials were kept in incubator chambers at 25 °C and 65% relative humidity for 65 d to measure progeny production. Complete parental mortality was observed in all cases for O. surinamensis and S. oryzae, but there was some survival for T. castaneum at 28 °C and 3 d of exposure. In general, progeny production was completely (100%) suppressed, with some exceptions for all species and populations. The results indicate that low oxygen is effective for all species tested, regardless of their resistance status to phosphine, and can be further adopted as an alternative method to mitigate resistance in stored product beetles.
Highlights
Phosphine, the most common fumigant in stored product protection, despite its proved efficacy in a wide range of application scenarios, is facing its bigger challenge: the development of resistanceInsects 2020, 11, 885; doi:10.3390/insects11120885 www.mdpi.com/journal/insectsInsects 2020, 11, 885 by many stored product insect populations in several parts of the world [1]
All laboratory populations were collected from Greece and maintained in Laboratory of Entomology and Agricultural Zoology (LEAZ) for more than 20 years, while O. surinamensis Def, T. castaneum QTC931 and S. oryzae 3Tusc were collected from Spain, Australia and Italy, respectively, and reared in LEAZ
Complete control of the parental adults was achieved at all nitrogen trials for both laboratory and field populations of O. surinamensis and S. oryzae, with the exception of T. castaneum laboratory populations (LB) and T. castaneum QTC931 in trials 3 and 5, respectively, which were carried out at either 28 ◦ C and 3 d or 28 ◦ C and 9 d (Table 2)
Summary
The most common fumigant in stored product protection, despite its proved efficacy in a wide range of application scenarios, is facing its bigger challenge: the development of resistanceInsects 2020, 11, 885; doi:10.3390/insects11120885 www.mdpi.com/journal/insectsInsects 2020, 11, 885 by many stored product insect populations in several parts of the world [1]. The most common fumigant in stored product protection, despite its proved efficacy in a wide range of application scenarios, is facing its bigger challenge: the development of resistance. Major stored product insects such as the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostryhidae); the rusty grain beetle, Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae); and the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) were found to be resistant to phosphine [1,2,3,4]. The increase in resistance populations worldwide necessitates the need for the use of alternative methods, either as standalone applications or as “resistance breakers” under a rotation concept with phosphine [1,4,5,6,7,8]. The utilization of contact insecticides has been proven to be effective for the control of populations that are resistant to phosphine, while several studies document the absence of cross resistance [10,11]
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