Comparative impacts of white grub (Coleoptera: Scarabaeidae) control products on the abundance of non-target soil-active arthropods in turfgrass

SummaryA study was conducted over 3 years on an experimental home lawn to detect, measure and contrast the effects of white grub (Coleoptera: Scarabaeidae) control products on the abundance of soil-active arthropods. Both short-term effects (those caused by a single application) and cumulative effects (those attributed to repeated yearly applications) were evaluated for five different control regimes: trichlorfon, imidacloprid, halofenozide, entomopathogenic nematodes and elemental sulfur. Treatments were applied to replicated plots (10 m×10 m) from 2000 to 2002. Invertebrates were sampled monthly from July to October in 2001 and 2002 by extracting soil cores in modified Tullgren funnels. All 293,868 captures were identified to class (arthropods) and order (hexapods). Overall extraction rate was 37,772 individuals/m2 of turf and associated topsoil. The ten most abundant taxa were analyzed in more detail to compare impacts across treatments. A consistent short-term effect due to individual applications was not detected. But when data were examined across both seasons, a significant cumulative effect of treatment was detected for total hexapods, Collembola, Thysanoptera and Coleoptera adults, but not oribatid mites, non-oribatid mites, Hymenoptera, Hemiptera, Coleoptera larvae or Diptera. Contrary to predictions, only imidacloprid – a systemic neonicotinoid applied early in the life cycle to target neonate white grubs – had a discernible impact on non-target abundance. Relative to the untreated check, it suppressed the abundance of those broad taxonomic groups by 54–62%. The implications of these results are discussed with respect to their functional relevance and to the role of neonicotinoids for white grub management in turfgrass.