Which pest is known to primarily damage soybean crops?

Spider mites are known to primarily damage soybean crops due to their feeding habits. These pests are small and can rapidly reproduce under certain environmental conditions, particularly in warm and dry weather. As they feed on the underside of soybean leaves, they extract sap, which can lead to discoloration, speckling, and overall stress on the plant. If the infestation is severe, it can result in reduced photosynthesis, leading to stunted growth, lower yields, and even plant death.

In contrast, the other pests mentioned, such as leafcutter ants, corn rootworm, and western corn rootworm, are more associated with different crops—leafcutter ants typically affect foliage of various plants but not soybeans specifically, while corn rootworm is primarily a pest of corn. Therefore, spider mites are the most relevant pest when it comes to direct damage on soybean crops.