Thermal requirements and population growth parameters of Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) on different wheat varieties in laboratory conditions

Sawtoothed grain beetle, Oryzaephilus surinamensis (L.)(Coleoptera: Silvanidae) isone of the major pests of stored products like stored wheat. In the current study, biology in laboratory, thermal requirements and population growth parameters of O. surinamensis were studied on five wheat varieties including Ghods, Mahdavi, Chamran, Kavir and Pishtaz. These experiments were carried out in growth chamber at 70±5% R.H and a photoperiod of 12 L: 12 D h.. Larval and pupal periods at 28±0.5⁰C showed no significant difference on various varieties. Average oviposition rate of female on different varieties were also compared. Each female laid 105.11±8.28 and 72.72±4.34 eggs on Ghods and Kavir varieties, respectively, showing the highest and the lowest oviposition rates among varieties. Effect of temperature on growth rate of immature stages was also studied at 20, 25, 28 and 30^°C on the five mentioned varieties. The results revealed that increasing temperature from 20 to 30^°C. decreased the larval and pupal periods. The thermal requirements of sawtoothed grain beetle were studied on the five wheat varieties. by keeping the insects at 15, 20, 25, 28 30 and 35^°C. The result showed the minimum larval T₀ was occurred on Chamran variety and the maximum on Ghods. The lowest pupal T₀ was observed on Pishtaz and the highest on Ghods. The lowest and the highest thermal constant of larval and pupal stage occurred on Ghods and Pishtaz, respectively. Comparison of population growth parameters revealed the highest (71.65 days) and the lowest (33.55 days) value of R₀ was on Mahdavi and Kavir, respectively. In these conditions the highest and lowest values of r_m were recorded on Mahdavi and Pishtaz varieties, respectively. The shortest doubling time (DT) (10.79 days) belonged to Mahdavi varietiy and the shortest generation time (65.16 days) was obtained on Chamran. The value of l showed no significant difference among varieties.