title: An experiment using neutron activation analysis and a rare earth element to mark cotton plants and two insects that feed on them.
abstract: Studies on insect dispersal and other behaviors can benefit from using markers that will not alter flight and fitness. Rare earth elements, such as samarium (Sm), have been used as ingested markers of some insects and detected using neutron activation analysis (NAA). In this study, samarium nitrate hexahydrate was mixed into artificial diet for boll weevils, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), at different dosages and in water used to irrigate cotton, Gossypium hirsutum L. Samarium was detected in adult boll weevils fed on the samarium-labeled diet, but not after 5 or 10 days of being switched to non-labeled diet, even if the insects were given labeled diet for as long as 7 consecutive days. Introduced in irrigation water, 1% samarium (m/m) was detectable in cotton squares and leaf tissue. However, boll weevil adults fed samarium-labeled squares did not retain detectable levels of samarium, nor did boll weevil adults reared to adulthood from samarium-labeled squares. Fourth instar beet armyworms, Spodoptera exigua (Hübner) (Noctuidae: Lepidoptera), fed on samarium-labeled cotton leaves obtained enough samarium for NAA detection, but adult moths reared from them did not have detectable amounts of samarium. Although samarium can be useful as a marker when insects are presented with a continuous pulse of the label, elements that are assimilated by the insect would be more useful if a continuous infusion of the marker cannot be provided.
authors.affiliation: USDA-ARS IFNRRU, Kika de la Garza Subtropical Agricultural Research Center, 2413 East Highway 83, Weslaco, TX 78596, USA. ashowler@eeslacoars.usda.gov
authors.forename: Allan T
authors.initials: AT
authors.lastname: Showler
authors.forename: William D
authors.initials: WD
authors.lastname: James
authors.forename: John S
authors.initials: JS
authors.lastname: Armstrong
authors.forename: John K
authors.initials: JK
authors.lastname: Westbrook
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000379:methods; D005247:Feeding Behavior / Q000502:physiology*; D003368:Gossypium / Q000469:parasitology* / Q000502:physiology*; D008674:Metals, Rare Earth / Q000032:analysis*; D009501:Neutron Activation Analysis / Q000379:methods*; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D012493:Samarium / Q000032:analysis; D018411:Spodoptera / Q000502:physiology*; D013194:Staining and Labeling / Q000379:methods
chemical_list: D008674:Metals, Rare Earth; D012493:Samarium