Synergism of a mixture of phosphine and carbon dioxide in fumigation against bean weevils

Abstract

The study is devoted to searching for alternatives to methyl bromide – a universal fumigant restricted in use at the request of the Montreal Protocol. Purpose: to determine the synergy of a mixture of phosphine and carbon dioxide in their various concentrations and exposures during the fumigation of leguminous products against pests at high temperatures. Methods: analytical review on the subject of research, the current regulatory framework in the field of disinfection; analysis of biological features of insect pests of leguminous products; experimental – a variation of different concentrations of phosphine, duration of exposure and temperature to establish a synergy of fumigant with carbon dioxide in laboratory conditions with appropriate equipment; mathematical and statistical – using computer mathematical functions built into the Microsoft Excel program 2003. When fumigating gas mixtures against pests at the imago stage, the optimal concentration of carbon dioxide is in the range of 110-130 g/m3 (or 5.5-6.5% of the total air volume), regardless of the temperature indicator. While the optimal concentration of phosphine at low temperatures (21-22°C) is in the range of 0.57-0.82 g/ m3, at high temperatures – (31-32°C) – in the range of 0.21-0.36 g/m3. With an increase in the duration of fumigation, not only the effectiveness of phosphine (standart) against the imago pests but also gas mixtures. In addition, the dependence of gas synergy on the duration of fumigation was established. Thus, at a temperature of 30°C, an increase in gas synergy in the mixture was observed by 4.4±0.66, 7.7±1.61, and 10.3±1.08% compared to the standard for exposure of 2, 4 and 6 hours, respectively. Temperature was the most determining factor influencing the value of the gas synergy index in the mixture of phosphine and carbon dioxide. Thus, an increase in temperature from 30°C to 32°C contributed to an increase in the gas synergy index by 9%, that is, by 2.17 times. Further establishment of lethal standards and fumigation regimes against pests, including quarantine ones, can prevent economic damage from these pests in Ukraine and will contribute to the implementation of the decisions of the Montreal Protocol aimed at protecting the environment and preventing the destruction of the ozone layer.