title: Substantial Mortality of Cabbage Looper (Lepidoptera: Noctuidae) From Predators in Urban Agriculture Is not Influenced by Scale of Production or Variation in Local and Landscape-Level Factors.
abstract: As Midwestern (United States) cities experience population decline, there is growing interest in converting underutilized vacant spaces to agricultural production. Urban agriculture varies in area and scope, yet most growers use similar cultivation practices such as avoiding chemical control of crop pests. For community gardens and farms that sell produce commercially, effective pest suppression by natural enemies is important for both societal, economic, and marketing reasons. To gauge the amount of prey suppression at 28 urban food-production sites, we measured removal of sentinel eggs and larvae of the cabbage looper Trichoplusia ni (Hubner), a caterpillar pest that defoliates Brassica. We investigated how landscape and local factors, such as scale of production, influence cabbage looper mortality caused by predators. Predators removed 50% of eggs and 25% of larvae over a 3-d period. Landscape factors did not predict mortality rates, and the amount of loss and damage to sentinel prey were similar across sites that differed in scale (residential gardens, community gardens, and farms). To confirm that removal of sentinel items was likely caused by natural enemies, we set up a laboratory assay that measured predation of cabbage looper eggs and larvae by several predators occurring in urban gardens. Lady beetles caused the highest mortality rates, suggesting their potential value for biocontrol; spiders and pirate bugs also consumed both eggs and larvae at high rates. Our results suggest that urban growers benefit from high consumption rates of cabbage looper eggs and larvae by arthropod predators.
authors.affiliation: Department of Biological Sciences, University of Illinois at Chicago, 845 W. Taylor St. (M/C 066), Chicago, IL 60607 (dmaxlow@gmail.com; mghare2@uic.edu).|Current address: Department of Horticulture, Oregon State University, 4017 Agriculture & Life Sciences, Corvallis, OR 97331 (david.lowenstein@oregonstate.edu).
authors.forename: David M
authors.initials: DM
authors.lastname: Lowenstein
authors.affiliation: Department of Biological Sciences, University of Illinois at Chicago, 845 W. Taylor St. (M/C 066), Chicago, IL 60607 (dmaxlow@gmail.com; mghare2@uic.edu).
authors.forename: Maryam
authors.initials: M
authors.lastname: Gharehaghaji
authors.affiliation: Department of Biological Sciences, University of Illinois at Chicago, 845 W. Taylor St. (M/C 066), Chicago, IL 60607 (dmaxlow@gmail.com; mghare2@uic.edu).|Institute for Environmental Science and Policy, University of Illinois at Chicago, 2121 West Taylor St. (MC 673), Chicago, IL 60612 (dhwise@uic.edu).
authors.forename: David H
authors.initials: DH
authors.lastname: Wise
mesh_terms: D000383:Agriculture; D000818:Animals; D001937:Brassica; D002641:Chicago; D002947:Cities; D020387:Food Chain; D007087:Illinois; D007814:Larva / Q000254:growth & development; D009036:Moths / Q000254:growth & development; D010063:Ovum / Q000254:growth & development; D010572:Pest Control, Biological
keywords: Brassica; city; lady beetle; sentinel prey