THE EFFECTS OF FIVE HERBICIDES ON THE NUMBERS OF CERTAIN INVERTEBRATE ANIMALS IN GRASSLAND SOIL

Abstract

Five herbicides, atrazine, dalapon, monuron, TCA, and 2,4-D, were applied once to grassland to evaluate their effects for at least two summers after application on the numbers of wireworms, Agriotes spp., springtails (Collembola suborder Arthropleona), mites (Acarina), earthworms (Lumbricidae), and millipedes (Diplopoda) in the soil. In plots treated with atrazine, wireworms, earthworms, and springtails declined in numbers. Dalapon increased the numbers of millipedes, springtails, and mites. Monuron reduced the numbers of wireworms, millipedes, earthworms, springtails, and mites. TCA increased the numbers of millipedes, springtails, and mites and decreased the number of earthworms. Treatment with 2,4-D did not affect the numbers of wireworms, springtails, or mites. The data suggest that faunal fluctuations were chiefly caused indirectly by the herbicides altering the floristic composition of the grassland.The results show that certain herbicides may diminish or increase the numbers of both beneficial and harmful soil animals. Under certain cultural conditions, herbicides as well as insecticides could fit into an integrated control program and help to counter the two threats of insect resistance to insecticides and excessive insecticide residues in soil.