Efficiency factors of phosphine in stored grain fumigation

Phosphine (PH3) remains the primary fumigant for protecting grain reserves in Russia. However, its efficiency depends on temperature, air humidity, pest development stages, and grain sorption. Optimal conditions are temperature +25...+30 °C and relative humidity 60–70 %. Temperature below 15 °C or humidity below 50 % sharply decreases the toxicity of phosphine. The authors analyse the differential sensitivity of pest development stages: larvae are highly susceptible, eggs – highly resistant. The paper highlights the molecular mechanisms of resistance (rph1, rph2 mutations), phosphine sorption by grain (20–40 %), and gas permeability. It includes practical recommendations for fumigation optimisation and resistance monitoring.