Conservation Biological Control and Pest Performance in Lawn Turf: Does Mowing Height Matter?

Abstract

With >80 million United States households engaged in lawn and gardening activities, increasing sustainability of lawn care is important. Mowing height is an easily manipulated aspect of lawn management. We tested the hypothesis that elevated mowing of tall fescue lawn grass promotes a larger, more diverse community of arthropod natural enemies which in turn provides stronger biological control services, and the corollary hypothesis that doing so also renders the turf itself less suitable for growth of insect pests. Turf-type tall fescue was mowed low (6.4 cm) or high (10.2 cm) for two growing seasons, natural enemy populations were assessed by vacuum sampling, pitfall traps, and ant baits, and predation and parasitism were evaluated with sentinel prey caterpillars, grubs, and eggs. In addition, foliage-feeding caterpillars and root-feeding scarab grubs were confined in the turf to evaluate their performance. Although some predatory groups (e.g., rove beetles and spiders) were more abundant in high-mowed grass, predation rates were uniformly high because ants, the dominant predators, were similarly abundant regardless of mowing height. Lower canopy temperatures in high-mowed grass were associated with slower growth of grass-feeding caterpillars. Higher lawn mowing reduces fuel consumption and yard waste, and promotes a deep, robust root system that reduces need for water and chemical inputs. Although in this study elevated mowing height did not measurably increase the already-high levels of predation, it did suggest additional ways through which bottom-up effects on insect pest growth might interact with natural enemies to facilitate conservation biological control.

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

“…Although we did not document which specific predators were responsible for the taking sentinel eggs or larvae in this study, ants were the only predators caught in the stickum on the hatch control egg sticks, and nearly all our incidental observations of predation were by ants. In a related study, ants accounted for ≥ 98 % of the 1220 total observed predation events on black cutworm eggs and larvae exposed in lawn grass during daytime and night (Dobbs and Potter 2014). It is probable that predation by the profuse ants in naturalized and mowed habitats eclipsed that contributed by other predator groups and is the main reason why there was no detectable spillover effect of biological control from naturalized areas.…”

“…Ants, especially L. neoniger, S. molesta and Pheidole sp., and other soil-nesting species that prefer open, sunny habitats, are the dominant predators on eggs and larvae of turfgrass pests in the northern two-thirds of the United States (Cockfield and Potter 1984;Lόpez and Potter 2000;Zenger and Gibb 2001;Royer and Walker 2004;Dobbs and Potter 2014). Ants as a group were ubiquitous in both naturalized and mowed roughs, with all three of the aforementioned types equally or more plentiful in the mowed turfgrass (Tables 1, 2) and no decrease in abundance with increasing distance naturalized-mowed boundaries.…”

“…Predatory invertebrates were abundant in both types of habitats, but pitfall traps in mowed turf revealed no differences in activity-density of major groups of predators at 1, 3, or 10 m distances from borders with naturalized roughs. Many spiders benefit from variation in vegetation height and structure for web construction (Gibson et al 1992;Dobbs and Potter 2014), so the taller vegetation and less frequent disturbance of the naturalized habitats likely account for the greater abundance of spiders (mostly Linyphiidae and Agelenidae) in vacuum samples from naturalized roughs. Sentinel eggs and larvae were heavily preyed upon in both types of habitats, but except for greater egg loss close to the edges of naturalized roughs at Kearney Hill, there was no decrease in predation at increasing distances from naturalized patches larvae (lower graph) exposed in naturalized roughs or mowed turfgrass at Kearney Hill into mowed turfgrass roughs.…”

“…Earlier studies (Lόpez and Potter 2000;Jo and Smitley 2003) also found less predation in fairways than in mowed grass roughs. Low-cut monoculture turf may be particularly inhospitable to some types of natural enemies; e.g., web-making spiders that benefit from vegetational complexity (Dobbs and Potter 2014) or omnivorous carabids that consume seeds as well as invertebrate prey (Blubaugh et al 2011).…”

Fungicides affect Japanese beetle Popillia japonica (Coleoptera: Scarabaeidae) egg hatch, larval survival and detoxification enzymes

“…Japanese beetle larvae are rarely found in golf course putting greens, but infestations can occur in areas directly adjacent to putting greens with identical soils and plant characteristics. The impacts of mowing height vary, depending on species, but there is limited evidence that grass height is a significant factor in survival of Japanese beetle larvae . Golf course putting greens often receive the most agrochemical inputs among areas on golf courses owing to high golfer standards and pest pressure, where numerous fungal diseases can damage turf under a variety of environmental conditions throughout the growing season .…”