Seasonal biology of the invasive green stinkworm Amynthas hupeiensis and control of its casts on golf putting greens

Amynthas hupeiensis (Michaelsen) is an invasive east Asian megascolecid earthworm whose prolific casting disrupted maintenance and playability of golf courses along the United States Atlantic seaboard during the 1940s and 1950s. The worm was recently found damaging sand-based greens of central Kentucky golf courses. This is the first report of A. hupeiensis infestation of golf courses west of the Appalachian Mountains and the first from golf courses anywhere in the United States in more than 60 years. We document A. hupeiensis seasonal biology and casting and evaluate chemical and organic vermicides for mitigating its damage on sand-based putting greens. Unlike ubiquitous European-origin earthworms that are active in golf course turf on native soil in early spring and late autumn, A. hupeiensis produces large, sinuate casts on sand-based greens, especially from May to September. Casting occurs day and night so that greens mowed in the morning are covered with new casts by afternoon. All life stages were present in greens from April to October. A single spring application of the neonicotinoid-pyrethroid combination insecticides clothianidin + bifenthrin (Aloft) or zeta-cypermethrin + bifenthrin + imidacloprid (Triple Crown) reduced casting by more than 95% for the rest of the growing season. Products with tea-seed saponins, concentrated pyrethrins, or soluble sulfur did not suppress casting by A. hupeiensis. We hypothesize that A. hupeiensis may be introduced onto golf courses as cocoons in compost, soil, or crude river sand used for course renovations, a scenario supported by events at our most egregiously infested study site and by confirmation of presence of A. hupeiensis along sandy riverbanks in Kentucky.