Influence Of Temperature, Relative Humidity And Interspecific Competition On The Population Growth Dynamics Of Three Pests Of Stored Product, Oryzaephilus surinamensis (L.), Sitophilus oryzae (L.) And Tribolium castaneum (Herbst)
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Date
2015-08
Authors
Goh, Xin Yu
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Abstract
The effects of temperature, relative humidity and interspecific competition on the population growth dynamics of three pests of stored product, Oryzaephilus surinamensis (Linnaeus), Sitophilus oryzae (Linnaeus) and Tribolium castaneum (Herbst) were investigated. These three species were reared under a range of temperatures (26-40°C) and relative humidities (RH) (7-85%). The estimated optimum growth temperature for O. surinamensis, S. oryzae and T. castaneum ranged from 29.61-33.96, 27.63-27.91 and 29.92-33.53°C, respectively, depending on RH. Lethal temperature of T. castaneum was the highest (40°C), followed by O. surinamensis (38°C) and S. oryzae (36°C). S. oryzae were unable to survive at extreme low RH (7%) at all temperatures tested. High RHs were generally beneficial to the population growth of all three species. In an attempt to elucidate the reaction of these species towards RH, water balance studies were carried out. Total body water content, water loss rate and cuticular permeability of O. surinamensis, S. oryzae and T. castaneum showed no significant difference from each other, implying that cuticular water loss was not the major cause of adult S. oryzae failed to survive at extreme low RH. These three species were then subjected to interspecific competition under different temperatures (20, 25, 30 and 35°C). Temperature has significant effect (p < 0.05) on the outcome of the interspecies competition.Oryzaephilus surinamensis was consistently the dominant species at all temperatures tested except 20°C. At 20°C, O. surinamensis were outnumbered when combined with either S. oryzae or T. castaneum. However, T. castaneum always outcompete S. oryzae when both species occurred together, irrespective of temperatures tested. The instantaneous population growth rate (ri) of S. oryzae was greatly reduced by T. castaneum. Oryzaephilus surinamensis also had slightly lower ri value when reared together with T. castaneum. Tribolium castaneum reared together with either O. surinamensis or S. oryzae had significantly higher ri value. The implications and the importance of these findings in the understanding of the abundances, distributions and pest status of these three pests of stored product are discussed
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Natural history