title: Video monitoring of brown planthopper predation in rice shows flaws of sentinel methods.
abstract: Immobilized preys are routinely used in agro-ecological exposure studies to quantify predation of pests under field conditions, but this method has not been validated. Our purpose was to determine the validity of using immobilized adults of the major rice pest Nilaparvata lugens, brown plant hopper (BPH), as sentinels. We used direct observation by video recording to determine the causal agents of removal of field exposed BPH sentinels with two experiments: 1) we recorded removal events of dead, immobilized BPH; and 2) we compared removal of (i) dead, immobilized BPH, (ii) live, immobilized BPH, and (iii) live, mobile BPH. Long-horned grasshoppers were responsible for most removals of dead, immobilized BPH, in both experiments. Predatory ground beetles removed most of the live, immobilized BPH, whereas frogs were the major predators of live, mobile BPH. Overall, we showed that removal of immobilized sentinel prey is not representative for predation of live, mobile prey, stressing the need for a critical assessment of commonly used sentinel methods. In addition, we found that frogs played the major role in predation of BPH in rice. As current strategies to enhance biocontrol of planthoppers in rice focus on arthropod natural enemies, this finding could have major implications.
authors.affiliation: Centre for Crop Systems Analysis, Wageningen University, Wageningen, The Netherlands.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zou
authors.affiliation: Department of Science, Open University, Heerlen, The Netherlands.
authors.forename: Joop
authors.initials: J
authors.lastname: de Kraker
authors.affiliation: Farming Systems Ecology, Wageningen University, Wageningen, The Netherlands.
authors.forename: Felix J J A
authors.initials: FJ
authors.lastname: Bianchi
authors.affiliation: Centre for Crop Systems Analysis, Wageningen University, Wageningen, The Netherlands.
authors.forename: Mario D
authors.initials: MD
authors.lastname: van Telgen
authors.affiliation: Institute of Entomology, Jiangxi Agricultural University, Nanchang, China.
authors.forename: Haijun
authors.initials: H
authors.lastname: Xiao
authors.affiliation: Centre for Crop Systems Analysis, Wageningen University, Wageningen, The Netherlands.
authors.forename: Wopke
authors.initials: W
authors.lastname: van der Werf
mesh_terms: D000818:Animals; D005247:Feeding Behavior; D006430:Hemiptera / Q000502:physiology*; D012275:Oryza / Q000469:parasitology*; D010802:Phylogeny; D011235:Predatory Behavior / Q000502:physiology*; D014741:Video Recording