Journal of Economic Entomology (2019) 112, 1975-1982

Manoj K. Nayak, Ramandeep Kaur, Rajeswaran Jagadeesan, Hervoika Pavic, Thomas W. Phillips and Gregory J. Daglish (2019)
Development of a quick knockdown test for diagnosing resistance to phosphine in Sitophilus oryzae (Coleoptera: Curculionidae), a major pest of stored products
Journal of Economic Entomology 112 (4), 1975-1982
Abstract: A key component in the management of resistance to fumigant phosphine in stored products pests is their early detection and implementation of control strategies. Currently, resistance testing involves exposing adults to a specific discriminating concentration over a fixed time period (20–48 h). Although it is widely adopted, this test takes significant time for assay preparation (up to 4 wk) as well as diagnosis (1–2 wk). To address these lacunae, we have established a 'quick knockdown test' using a key grain insect pest, rice weevil, Sitophilus oryzae (L.). Susceptible, weakly and strongly phosphine-resistant reference strains were exposed to a threshold concentration of phosphine over short exposure periods (min to h). The time to knockdown (KT) responses to phosphine were characterized at 2 (1,440 ppm) and 5 mg/liter (3,600 ppm). The time to 99.9% KT (KT_99.9) at 2 mg/liter was 12.52 min for the susceptible adults, compared with 167.9 and 1,510 min in the case of weakly and strongly resistant phenotypes, respectively. As anticipated, increasing the concentration of phosphine to 5 mg/liter halved the KT_99.9 (81.57 min) to separate weakly and strongly resistant populations than it was required at 2 mg/liter. We validated the KT_99.9 value for the 5 mg/liter against field-derived populations of S. oryzae. The results were aligned with the existing Food and Agriculture Organization approach, confirming that the proposed 'quick test' is a reliable tool to rapidly diagnose resistance in this species.
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Link to article at publishers website
Database assignments for author(s): Manoj K. Nayak, Thomas W. Phillips

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Sitophilus oryzae