Abstract:To evaluate the relationship between the population density of underground insect pests and degree of damage on the host, insect pest species and population number of each species were examined before wheat being sowed in autumn. Meanwhile, wheat seedling death rates at different development stages were investigated using chessboard sampling method in Wugong, Shaanxi Province. A total of 20 soil insect pest species were found in the tested wheat fields before wheat being sowed in autumn. Wireworms and grubs were the dominant pest species, up to 58.66% and 21.91% of all the soil insect pests, respectively. Soil insect pests resulted in the higher seedling death rate from 4.4% to 9.1% during fall-seedling stage than that from 1.0% to 2.3% during turning-green stage. Correlation analysis showed that seedling death rates caused by soil insect pests were significantly correlated with their population densities at both fall-seedling and turning-green stages.