Dynamics of Earthworm Population in Turfgrass Systems: Impact of Management Intensities and Pesticides.

Earthworms play a variety of important roles in turfgrass systems through enhancing soil aeration, water filtration, and thatch mixing and decomposition. Too many earthworms may, however, lead to uneven playing surfaces, soil erosion and new niches favorable to weed invasion. Also, earthworm casting poses a significant challenge for golf course managements across the world. We investigated population dynamics of earthworms in different management history (10 years vs 80 years) and management intensities [rough- (the Rough) vs intensive-(the Fairway) managements] in field and examined the impact of eight common pesticides (4 fungicides and 4 insecticides) on earthworm feeding and burrowing behaviors in controlled environments. Population and biomass of earthworms did not show significant differences between the old (80 years) and the young (10-years) fairways, but were found to be greater in the Rough than in the Fairway. Soil moisture and temperature had a dominant effect on earthworm density and activities. Pesticides also affect earthworm population dynamics and activities. Single application of insecticides Sevin and Merit at the manufacturers’ maximum dosages significantly inhibited burrowing behaviors of earthworms for at least three weeks without leading to any earthworm death. The toxicity to earthworms, however, increased as application frequency increased. Weekly applications of chemicals Sevin, Merit and 3336 for four weeks led to the mortality at 35, 45 and 80%, respectively. These findings suggested that earthworm activities in turfgrass systems may be optimized through water and chemical managements.