Tolerance Research to Phosphine on Cynaeus angustus(Leconte)Compared with Tribolium castaneum(Herbst)and Cryptolestes ferrugineus(Stephens)
There is no information on research of large black flour beetle,Cynaeus angustus,a potential insect of stored grain.Knowing the tolerance to phosphine fumigation of this insect is benefit to the scientific management.The median knock-down time(KT50)and the toxicity data of C.angustus was determined by knockdown method and re-sistance measurement method recommended by FAO,and compared with the phosphine-resistant strains of Triboli-um castaneum and Cryptolestes ferrugineus correspondingly.The mortality in process and full mortality of eggs,lar-vae,pupae and adults for all three species were determined when phosphine concentration at 100,200,300,400 mL/m3 and 500 mL/m3.The KT50 values of phosphine were 7,127 min and 3 736 min to C.angustus,T.castane-um,and C.ferrugineus.The slope b values in the toxicity regression equation were 3.67,8.28 and 9.94,and the LC50 values were 0.008,1.34 mg/L and 5.88 mg/L,relatively.The LT50 values of phosphine at 100,200,300,400 mL/m3 and 500 mL/m3 were 4～2 h for egg stage of C.angustus,4～1 h for larvae,4～1 h for pupae,and 3～1 h for adults.LT50 values were 12～5 d for egg stage of T.castaneum,11～5 d for the larvae,13～7 d for the pu-pae,and 10～4 d for the adults.LT50 values were 28～13 d for egg stage of C.ferrugineus,18～9 d for the larvae,26～11 d for the pupae,and 17～9 d for the adults.The complete lethal time(LT100)values were 21～6 h for egg stage of C.angustus,8～3 h for larvae,9～6 h for pupae,and 5～3 h for adults.The LT100 values were 21～18 d for egg stage of T.castaneum,21～15 d for the larvae,27～18 d for the pupae,and 21～12 d for the adults.The LT100 values were 54～30 for egg stage of C.ferrugineus,42～30 d for the larvae,48～30 d for the pupae,and 36～25 d for the adults.The tested C.angustus population was a susceptible strain,and the tolerance arrangement to phosphine of different stages was egg＞pupa＞larvae＞adult.The tolerance to phosphine of C.angustus was sig-nificantly low compared with resistant strains of T.castaneum and C.ferrugineus.
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