Which one of the following types of pesticides is convenient to control stored grain pests ?

Fumigants are the most convenient and effective type of pesticide for controlling stored grain pests because they act in a gaseous state, allowing them to penetrate deep into grain bulks, silos, and packaged commodities [2]. Unlike contact or stomach poisons, which require direct physical interaction with the pest or ingestion, fumigants like phosphine (aluminum phosphide) and methyl bromide can reach all life stages of insects, including those developing inside the grain kernels. This gaseous diffusion is critical for treating large-scale storage facilities where physical application of sprays is impractical [2]. While contact insecticides are used as residual protectants to prevent new infestations, fumigation is the primary method for eliminating existing infestations in stored products. Stack fumigation is specifically noted as a highly practicable and convenient method for treating stored grains in various storage environments [2].

Sources

1. [1] https://npponepal.gov.np/progressfiles/Training-Manual-on-AlPH3-Fumigation_1549364287-1701156938.pdf
2. [2] https://www.fao.org/4/x5065e/x5065E0g.htm