Evaluation of three diatomaceous earth and one natural pyrethrum formulations against pupae of Tribolium confusum DuVal (Coleoptera: Tenebrionidae) on wheat and flour

Abstract

Abstract Laboratory tests evaluated the effect of three diatomaceous earth (DE) and one natural pyrethrum formulations, against pupae of the confused flour beetle, Tribolium confusum DuVal (Coleoptera: Tenebrionidae) on wheat and flour. The formulations were Silicosec ® , containing 92% SiO 2 , Pyrisec ® , which contains Silicosec with 1.2% natural pyrethrum and 3.1% piperonyl butoxide (PBO) and Insecto ® , containing 86.7% SiO 2 and 10% food-grade additives. To evaluate the impact of natural pyrethrum alone, PBK ® polvere (Copyr S.p.a, Tradate, Italy), containing 0.8% natural pyrethrum and 2.1% PBO was also tested. Pupae were exposed to the above formulations at 25 and 30 °C and 65% rh. The DE formulations were applied at two dose rates 500 and 1000 ppm, and PBK ® polvere at 750 and 1500 ppm. Pupae of two ages were examined, 1-d and 5-d old. After 8 d exposure, in the case of 1 d old pupae, and 4 d exposure, in the case of 5 d old pupae, the emergence of T. confusum adults was measured. In addition, 7 d after emergence, mortality of the emerged adults was recorded. Temperature had no effect on adult emergence. Silicosec ® and Insecto ® did not affect emergence, since all pupae on treated commodities successfully emerged into adults. In contrast, the other two formulations significantly decreased adult emergence. Also, with these two formulations, significantly more adults were emerged on flour than on wheat. Furthermore, adult emergence was significantly higher in 5-d old pupae than in 1-d old ones. Mortality of the emerged adults was noted with all formulations tested and ranged between 34% and 100%.