Phosphine-resistance in 92 strains of major stored grain insects collected from 55 grain reserves in 23 provinces or municipalities
of the country were detected through the method recommended by FAO.The result showed that the susceptible strains,slight-
resistant strains,middle-resistant strains,high-resistant strains and super-resistant strains accounted for 54.3%,9.8%,7.6%,13.0%,15.2% of the total strains respectively.The dominating high-resistance species of insects investigated were Cryptolestes Ferrugineus,Rhizopertha dominica and Sitophilus Oryzae. Among them,resistance in Cryptolestes Ferrugineus was more serious generally,and in Rhizopertha dominica and Sitophilus Oryzae increased 71.2% and 10.7% respectively within the latest 8 years,according to comparison to the
investigation in 1995.Southwest,middle and south areas of China were the major zones investigation areas in 1995.Southwest,middle and south areas of China were the areas zones where resistance to phosphine in stored grain insects developed relatively significant.