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Nontarget herbivory by a weed biocontrol insect is limited to spillover, reducing the chance of population‐level impacts
Insects approved for classical biocontrol of weeds are often capable of using close relatives of their target weed for feeding, oviposition, or larval development, with reduced preference and performance. When nontarget herbivory occurs and is suspected to reduce survival, growth, or fecundity of individual plants, and insects are capable of reproducing on their nontarget host, characterization of spatial and temporal patterns of the occurrence and intensity of herbivory is valuable for predicting potential population‐level effects. Here, we perform a novel post‐release manipulative field experiment with a root‐feeding biocontrol weevil,Mogulones crucifer, released in Canada to control the rangeland weedCynoglossum officinale, to test for its ability to establish on the nontarget plantHackelia micrantha. AfterCynoglossum,M. cruciferexhibits its highest preference for and performance onHackeliaspp. We releasedM. cruciferon Canadian rangeland sites with naturally occurring populations ofH. micranthagrowing interspersed with the target weed or in the near absence of the target weed. Adult weevil feeding on surrounding plants was monitored for three summers after release (years 0, 1, and 2), and, subsequently, subsets of plants were destructively sampled to determineM. cruciferoviposition levels. Additional oviposition and larval development data were obtained from seven non‐experimental sites where weevils were released zero, three, or four years earlier.M. cruciferwas not detected on experimental sites withoutC. officinaleafter two years, and nontarget herbivory was restricted to rare, low‐level spillover. Visible evidence of adult herbivory (i.e., scars on shoots) was associated with oviposition in 90% of targets but only 30% of nontarget plants. We infer, through ecological refuge theory, that nontarget population‐level impacts fromM. cruciferspillover are unlikely because of temporal, spatial, and probabilistic refuges from herbivory, and make recommendations for monitoring and management of biocontrol systems with similar attributes, such as removing target plants around nontarget populations of interest. BecauseM. cruciferis among the least host‐specific of the modern weed biocontrol agents, andH. micranthais likely one of its most highly preferred nontargets, these conclusions are, arguably, generally applicable to other nontarget plants and biocontrol systems.
Nontarget herbivory by a weed biocontrol insect is limited to spillover, reducing the chance of population‐level impacts
Insects approved for classical biocontrol of weeds are often capable of using close relatives of their target weed for feeding, oviposition, or larval development, with reduced preference and performance. When nontarget herbivory occurs and is suspected to reduce survival, growth, or fecundity of individual plants, and insects are capable of reproducing on their nontarget host, characterization of spatial and temporal patterns of the occurrence and intensity of herbivory is valuable for predicting potential population‐level effects. Here, we perform a novel post‐release manipulative field experiment with a root‐feeding biocontrol weevil,Mogulones crucifer, released in Canada to control the rangeland weedCynoglossum officinale, to test for its ability to establish on the nontarget plantHackelia micrantha. AfterCynoglossum,M. cruciferexhibits its highest preference for and performance onHackeliaspp. We releasedM. cruciferon Canadian rangeland sites with naturally occurring populations ofH. micranthagrowing interspersed with the target weed or in the near absence of the target weed. Adult weevil feeding on surrounding plants was monitored for three summers after release (years 0, 1, and 2), and, subsequently, subsets of plants were destructively sampled to determineM. cruciferoviposition levels. Additional oviposition and larval development data were obtained from seven non‐experimental sites where weevils were released zero, three, or four years earlier.M. cruciferwas not detected on experimental sites withoutC. officinaleafter two years, and nontarget herbivory was restricted to rare, low‐level spillover. Visible evidence of adult herbivory (i.e., scars on shoots) was associated with oviposition in 90% of targets but only 30% of nontarget plants. We infer, through ecological refuge theory, that nontarget population‐level impacts fromM. cruciferspillover are unlikely because of temporal, spatial, and probabilistic refuges from herbivory, and make recommendations for monitoring and management of biocontrol systems with similar attributes, such as removing target plants around nontarget populations of interest. BecauseM. cruciferis among the least host‐specific of the modern weed biocontrol agents, andH. micranthais likely one of its most highly preferred nontargets, these conclusions are, arguably, generally applicable to other nontarget plants and biocontrol systems.
Nontarget herbivory by a weed biocontrol insect is limited to spillover, reducing the chance of population‐level impacts
Ecological Applications
Catton, Haley A. (author) / Lalonde, Robert G. (author) / De Clerck-Floate, Rosemarie A. (author)
Ecological Applications ; 25 ; 517-530
2015-03-01
Article (Journal)
Electronic Resource
English
Volatile Compound Chemistry and Insect Herbivory: Pinus edulis Engelm. (Pinaceae) Seed Cone Resin
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