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Insecticidal potential of natural zeolites and diatomaceous earths originating from Serbia against Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) was evaluated. Two natural zeolite formulations (NZ and NZ Modified) were applied to wheat at rates of 0.50, 0.75, and 1.0 g/kg, while two diatomaceous earth (DE) formulations (DE S-1 and DE S-2) were applied at rates of 0.25, 0.50, 0.75, and 1.0 g/kg. A bioassay was conducted under laboratory conditions: temperature of 24 +/- 1 degrees C, relative humidity in the range 50-55%, in tests with natural zeolites, and 60-65%, in tests with DEs, and in all combinations for progeny production. Mortality was assessed after 7, 14, and 21 d of insect contact with treated wheat, and the total mortality after an additional 7-d recovery on untreated broken wheat. Progeny production was also assessed after 8 wk for S. oryzae and 12 wk for T. castaneum. The highest mortality for S. oryzae and T. castaneum was found after the longest exposure period and 7 d of recovery, on wheat treated with NZ at the highest rate and DEs at rates of 0.50 -1.0 g/kg. Progeny reduction higher than 90% was achieved after 14 and 21 d of contact of both beetle pests with wheat treated with DE S-1 at 0.50-1.0 g/kg and DE S-2 at 0.75-1.0 g/kg, while the same level of reduction was achieved only for T. castaneum after its contact with the highest rate of NZ formulation. NZ Modified, applied even at the highest rate, revealed much lower insecticidal potential.

No abstract

A study of the biological features and the potential population growth between two laboratory strains of the confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) from Greece and Serbia is conducted on cracked barley and cracked white rice. The results show that, at a species level, T. confusum is able to complete development on cracked barley but not on cracked white rice. Therefore, cracked white rice proves to be an unsuitable commodity for T. confusum. Larval development on cracked barley is significantly shorter for the Serbian compared to the Greek strain (37.7 and 49.7 days, respectively), but pupal development does not differ between the two strains (6.2 days for both strains). Additionally, male longevity does not differ between the Greek and Serbian strains (144.4 and 151.4 days, respectively), while female longevity is significantly shorter for the Serbian (151.7 days) compared to the Greek strain (186.6 days). Fecundity does not differ between the two strains (11.3 and 17.7 eggs/female for the Greek and the Serbian strain, respectively), whilst survival is higher for the Serbian strain on both tested commodities. The values of the net reproductive rate, the intrinsic rate of increase and the finite rate of increase on cracked barley are significantly higher for the Serbian (7.27 females/female, 0.025 female/female/day and 1.026, respectively) compared to the Greek strain (2.91 females/female, 0.014 females/female/day and 1.014, respectively). It therefore is expected that different strains of T. confusum may exhibit variable phenology as well as potential population growth. Additionally, we expect our results to have bearing on the management of this species.