Red nematodes are pests. Red nematodes, also known as filariasis and water worms, are called thread snakes in the north. Red nematode is an important pest in rice diseases and insect pests, which mainly appears in rice growth period. Red nematodes attack rice roots, causing damage to rice roots and even causing root death. Red nematodes are aquatic oligochaetes in annelids. They are bright red or blue-gray, and look like earthworm larvae. They are aquatic oligochaetes in annelids, slender, with a body length of 4 cm and a maximum length of 10 cm. Red nematodes mostly live in the silt on the bank or bottom of the river, which is dense with the surface of the silt. One end is fixed in the silt, and the other end gives birth to silt that vibrates in the water.