Low temperature tolerance of Plodia interpunctella, Sitophilus oryzae and Sitophilus zeamais: The prevalent pests of stored maize in Serbia

Insect's bionomics and development are highly dependent on the environmental temperature. For centuries, this fact has been used for the control of storage pests. However, the temperature threshold depends on the species, life stage, acclimation and exposure period. This work assessed the effects of low temperatures (4,-4,-10,-15 and-18°C) and exposure period (10, 30, 60, 120 and 180 min) on the survival and development of Plodia interpunctella larvae, and adults of Sitophilus oryzae and S. zeamais, the prevalent maize pests in Serbia. Data were analysed using one-way and two-way ANOVA. Additionally, Probyt analysis was performed to determine the LT 50 and LT 99. The first significant effects were recorded at-4°C for S. oryzae when the mortality was 41% after 120 and 52% after 180 min of exposure. At-10°C, the mortality of S. zeamais was significant after 180 min (52.5%) and increased with the exposure period. The significant mortality of P. interpunctella larvae was at-15°C after 10 min (55.5%). At-18°C, P. interpunctella larvae were the most susceptible and 98% of mortality was recorded after 10 min, while 77.5% of S. oryzae and 68% of S. zeamais was recorded after 10 min. Two-way ANOVA showed that both factors (temperature and exposure) significantly affected the mortality of tested species, but the first factor was the most influential. These results indicate that temperature and exposure period should be adjusted to specific pest, while in combined infestations the temperature should be adjusted to the most tolerant one.