Phosphine: an eco-friendly alternative for management of wheat storage insects

Methyl bromide (MB) fumigant has been phased out in many countries honouring Montreal Protocol. Reports on phosphine fumigant efficacy under different ecological zones in India are scanty. Field fumigation trials were conducted on 5 Metric Tons of wheat stacks per replication of a treatment for testing phosphine efficacy against laboratory cultured and resident population of Tribolium castanium, Sitophilus oryzae, and Rhyzopertha dominica. The trials were organized in triplicate including control at two locations with varying climate locations namely, Pithoragarh and Delhi using conventional 56% tablet (2 and 3 tablet/MT) and 77.5% granular (1.0 and 1.5 g phosphine/m3) formulations of Aluminium phosphide (AlP) for 7 and 10-days exposure periods for each dosage. Phosphine concentration was monitored every 24 hours till end of the exposure periods. Insect mortality of laboratory culture and resident infestation was observed as 100% in both the exposure periods using all dosages of phosphine. No emergence of insects was observed till 60 days after treatment at both the locations, indicating mortality of all available life stages of insects during the exposure periods. Minimum effective phosphine concentration for controlling all life stages of S. oryzae, R. dominica and T castaneum was observed 500-600 ppm for 7-days exposure at 25{degrees}-27{degrees}C and humidity 38-45%, at 1.5 g phosphine/m3. Hence, phosphine can be an effective alternative to methyl bromide fumigant for wheat stored grain insects at different climatic conditions.