Comparison between using phosphine and/or carbon dioxide for controlling Plodia interpunctella and Oryzaephilus surinamensis in stored date fruits

This experiment aimed to evaluate the use of CO2 and phosphine gas, each alone and mixed together, in controlling Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) and Oryzaephilus surinamensis (Linnaeus) (Coleoptera: Silvanidae) which infesting stored date fruits.The study also aimed to evaluate the effect of using these gases on the chemical properties and quality of the treated date fruits.Three concentrations of CO2 (50, 75 and 100%) were tested to control the two insects for different exposure times ranged from 1 to 36 hrs.The obtained results showed that the corrected mortality percentage of the two tested insects increased by increasing the exposure time in each of the three CO2 concentrations, and or increasing of the concentration.The corrected mortality percentages of P. interpunctella and O. surinamensis reached 100% after exposure to CO2 (50, 75 &100%) for exposure periods (36, 24 &16 hrs.) respectively.For phosphine gas five concentrations were tested (0.073, 0.146, 0.292, 0.585 and 1.170 g.) of magnesium phosphide .The results of phosphine showed that the corrected mortality percentage of the two tested insects increased by increasing the concentration of phosphine, Where the corrected mortality percentages recorded (36.67, 53.33, 66.67, 83.33 and 100%) for P. interpunctella larvae, and (23.33, 36.67,50.00, 66.67 and 100% ) for O. surinamensis adults when exposed to the mentioned phosphine concentrations.When LC50 of CO2 was mixed with LC50 of phosphine, the mortality percentages of the two tested insects increased and reached the maximum 100% by using the mixture containing (CO2 + phosphine) Such level of mortality could be never obtained when CO2 or phosphine was used each alone at these concentrations.Thus, we reduced the amount of phosphine gas used and increased its efficiency.Data showed clearly that P. interpunctella larvae was more susceptible to the two tested gases alone or mixed than the adults of O. surinamensis.The results showed that the gases used in the experiment had no effect on the chemical properties of the treated date fruits compared to the control, especially the mixture of gases, except in the case of treatment with carbon dioxide and phosphine gas, both of them separately, which only increased the total phenols in the fruits.