Management Practices to Promote Downward Abamectin Distribution in the Soil Profile.

Abamectin is a nematicide for control of many nematode species in golf course putting greens; however, high sorption to accumulated organic matter near the soil surface in established turfgrass systems may limit its distribution in soil thereby limiting its efficacy.  Field research was initiated August 12, 2015 in Raleigh, NC on a creeping bentgrass (Agrostis stolonifera L.) putting green to evaluate cultural and application practices to promote downward abamectin distribution in the soil profile.  Practices included various combinations of hollow- or solid-tine aerification (7.5 cm depth) in tandem with topdressing prior to abamectin application (75 g ai ha^-1), as well as abamectin injection via Dryject^® equipment.  Following abamectin application, soil cores (15 cm diameter x 25 cm depth) were collected from plots 1, 7, 14 and 28 d after treatment (DAT) and segmented into thatch, 0 to 2.5, 2.5 to 5, 5 to 7.5, 7.5 to 10, 10 to 15 and 15 to 20 cm depth increments.  Compared to broadcast spray which did not result in abamectin distribution beyond 2.5 cm, all practices increased downward distribution in soil.  Hollow-tine aerification treatments resulted in 7 to 13% of the applied abamectin at 5 to 7.5 cm, 14 DAT, while solid-tine aerification resulted in 17% of the applied at 5 to 7.5 cm.  Additionally, solid-tine aerification resulted in distribution in the 7.5 to 10 cm depth (3% of applied at 14 DAT), while hollow-tine treatments did not.  Dryject^® treatments increased downward abamectin soil distribution 1 DAT, with >20% of the applied detected in all depth increments from 5 to 15 cm.  Results from this research will provide practitioners pertinent information to improve abamectin efficacy for nematode control on golf course putting greens.