title: Pyrethrins protect pyrethrum leaves against attack by western flower thrips, Frankliniella occidentalis.
abstract: Pyrethrins are active ingredients extracted from pyrethrum flowers (Tanacetum cinerariifolium), and are the most widely used botanical insecticide. However, several thrips species are commonly found on pyrethrum flowers in the field, and are the dominant insects found inside the flowers. Up to 80% of western flower thrips (WFT, Frankliniella occidentalis) adults died within 3 days of initiating feeding on leaves of pyrethrum, leading us to evaluate the role of pyrethrins in the defense of pyrethrum leaves against WFT. The effects of pyrethrins on WFT survival, feeding behavior, and reproduction were measured both in vitro and in planta (infiltrated leaves). The lethal concentration value (LC50) for pyrethrins against WFT adults was 12.9 mg/ml, and pyrethrins at 0.1% (w/v) and 1% (w/v) had significantly negative effects on feeding, embryo development, and oviposition. About 20-70% of WFT were killed within 2 days when they were fed chrysanthemum leaves containing 0.01-1% pyrethrins. Chrysanthemum leaves containing 0.1% or 1% pyrethrins were significantly deterrent to WFT. In a no-choice assay, the reproduction of WFT was reduced significantly when the insects were fed leaves containing 0.1% pyrethrins, and no eggs were found in leaves containing 1% pyrethrins. Our results suggest that the natural concentrations of pyrethrins in the leaves may be responsible for the observed high mortality of WFT on pyrethrum.
authors.affiliation: Plant Research International, Wageningen UR, P.O. Box 619, 6700 AP, Wageningen, The Netherlands.
authors.forename: Ting
authors.initials: T
authors.lastname: Yang
authors.forename: Geert
authors.initials: G
authors.lastname: Stoopen
authors.forename: Gerrie
authors.initials: G
authors.lastname: Wiegers
authors.forename: Jing
authors.initials: J
authors.lastname: Mao
authors.forename: Caiyun
authors.initials: C
authors.lastname: Wang
authors.forename: Marcel
authors.initials: M
authors.lastname: Dicke
authors.forename: Maarten A
authors.initials: MA
authors.lastname: Jongsma
mesh_terms: D000818:Animals; D011723:Chrysanthemum cinerariifolium / Q000378:metabolism*; D005247:Feeding Behavior / Q000187:drug effects; D005260:Female; D007302:Insect Repellents / Q000378:metabolism*; D007306:Insecticides / Q000378:metabolism*; D010058:Oviposition / Q000187:drug effects; D018515:Plant Leaves / Q000378:metabolism*; D011722:Pyrethrins / Q000378:metabolism*; D061149:Thysanoptera / Q000502:physiology
chemical_list: D007302:Insect Repellents; D007306:Insecticides; D011722:Pyrethrins