Naturalized habitat on golf courses: source or sink for natural enemies and conservation biological control?

Many golf courses are converting out-of-play areas to meadow-like habitat to reduce mowing, irrigation, and chemical inputs. Such naturalized roughs, which often constitute 50 % or more of a course’s total acreage, support biodiversity by providing habitat for pollinators and other wildlife. This study explored the hypothesis that they also serve as reservoirs of invertebrate natural enemies whose services extend to suppress pests in adjacent mowed turf. We used vacuum sampling, pitfall traps, and ant baits to compare arthropod populations in grassland or meadow-type naturalized roughs and traditional mowed roughs at two courses, and tested for spillover of biological control using sentinel eggs or larvae of a grass-feeding caterpillar exposed near or farther from naturalized areas into mowed turf. Although some natural enemies (e.g., spiders) were more abundant in naturalized roughs, we saw no direct spillover of predation which was quite high regardless of habitat type. Most likely that is because ground-nesting ants (Lasius, Solenopsis, and Pheidole spp.), which are dominant predators in this system, were equally or more abundant in the mowed turfgrass. Herbivorous insects, too, were more abundant in naturalized roughs, so prey availability may discourage solitary ground-dwelling predators from leaving those refuges to forage in mowed areas. There was no parasitism of sentinel eggs or larvae in our trials. Despite absence of direct spillover of predation, we argue that naturalized roughs might be more purposely designed and managed to promote parasitoids, insectivorous birds, and other enemies that provide diffuse biological control services elsewhere on the course.