Immediate and delayed mortality of the larger grain borer, Prostephanus truncatus (Horn), on different surfaces treated with thiamethoxam and alpha-cypermethrin I. Doganay a , P. Agrafioti b , A.A. Isikber a , O. Saglam c , C.G. Athanassiou b, * a Kahramanmaras ¸ Sütçü _ Imam University, Agriculture Faculty, Plant Protection Department, Avs ¸ar Campus, 46100, Kahramanmaras ¸ , Turkey b Laboratory of Entomology and Agricultural Zoology, Department of Agriculture, Crop Production and Rural Environment, University of Thessaly, Phytokou str., Nea Ionia, Magnesia, 38446, Greece c Namık Kemal University, Agriculture Faculty, Plant Protection Department, 59030, Tekirdag, Turkey article info Article history: Received 26 August 2017 Received in revised form 3 October 2017 Accepted 6 October 2017 Keywords: Prostephanus truncatus Alpha-cypermethrin Thiamethoxam Treated surfaces Delayed mortality abstract In this study, we evaluated efficacy of alpha-cypermethrin and thiamethoxam on concrete, linen and plastic surfaces, against adults of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae), which is an important pest of stored maize in the tropics. Insect mortality was recorded after 1, 3 and 7 days of exposure. Then, separately for each initial exposure, the surviving individuals were transferred to untreated surfaces and delayed mortality was assessed again 1, 3 and 7 days later. Adult mortality on both insecticide treated linen surface was significantly lower than those on the other surfaces. Regarding delayed mortality, for adults that had been initially exposed for 7 d, complete control was detected 7 d later on plastic and concrete surfaces treated with thiamethoxam, while for alpha- cypermethrin complete mortality was detected only on plastic surface. Overall, there was a noticeable delayed mortality of P. truncatus adults, for all exposures and surfaces, which indicates that even if the insects are removed from the substrate that with either alpha-cypermethrin or thiamethoxam, delayed mortality is more likely to occur than recovery. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction The larger grain borer, Prostephanus truncatus (Horn) (Coleop- tera: Bostrychidae), was introduced and reported for the first time in sub-Saharan Africa in the early 1980s, and then established rapidly in many parts of Central Africa (Hodges, 1986; Borgemeister et al., 1997). Currently this species is now spread in 16 African countries (Nansen and Meikle, 2002; EPPO, 2016). Moreover, P. truncatus has been intercepted in several other countries worldwide, such as Israel (Calderon and Donahaye, 1962), Iraq (Al- Sousi et al., 1970), and USA (EPPO, 2016). Recently, adults of P. truncatus have been detected in European countries such as Italy (Suma and Russo, 2005), Germany (Scholler, 2013) and France (EPPO, 2016). Heavy infestations of this species have been shown to occur on maize and dried cassava (Dunstan and Magazini, 1981; Golob and Hodges, 1982; Hodges et al., 1983), but it can also infest a wide range of other durable commodities, however development in small grains is less likely to occur, for reasons that are not fully understood so far (Hodges, 1986; Athanassiou et al., 2017). On maize, it completely destroys the commodity often in less than one month (Hodges, 1986; Kumar, 2001; Nansen et al., 2002), while it is able to infest stored cobs, as well as cobs in the field (Hodges, 1986; Nansen et al., 2002). Hodges (1986) reported that P. truncatus can cause losses up to 40% for maize cobs and up to 70% for dried cassava roots after 6 and 4 months of storage, respectively. Similarly, high dry weight losses have been reported for stored maize (Pantennius, 1988; Muatinte et al., 2014) and dried cassava (Hodges et al., 1985; Borgemeister et al., 1997). Prostephanus truncatus is tolerant to organophosphorus com- pounds (OPs), which are usually effective for the control of other major stored product beetle species on maize (Golob, 2002; Rumbos et al., 2013). Nevertheless, P. truncatus is considered sus- ceptible to pyrethroids, such as deltamethrin and permethrin (Golob et al., 1983, 2002). Deltamethrin and beta-cyfluthrin pro- vided a satisfactory level of protection on treated maize against P. truncatus (Golob and Hanks, 1990). However, the efficacy of * Corresponding author. E-mail address: athanassiou@agr.uth.gr (C.G. Athanassiou). Contents lists available at ScienceDirect Journal of Stored Products Research journal homepage: www.elsevier.com/locate/jspr https://doi.org/10.1016/j.jspr.2017.10.003 0022-474X/© 2017 Elsevier Ltd. All rights reserved. Journal of Stored Products Research 76 (2018) 1e6