ARS | Publication request: Changes in trace metals in hemolymph of baculovirus infected noctuid larvae

Submitted to: Biological Trace Element Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 28, 2011
Publication Date: May 4, 2012
Citation: Popham, H.J., Sun, R., Shelby, K., Robertson, D. 2012. Changes in trace metals in hemolymph of baculovirus-infected noctuid larvae. Biological Trace Element Research. 146:325-334.

Interpretive Summary: The levels of available micronutrients, such as iron and zinc, influence the extent of infection by an insect pathogen. Therefore it is likely that micronutrient levels present in crops may help or hinder the usefulness of an insect virus used as a biological control agent for an insect pest. In this study, the blood levels of nine metal micronutrients were measured during a viral and bacterial infection of the pest moths, the budworm and the earworm. Viral infection of caterpillars from both species altered the blood levels of iron, zinc, copper, magnesium, molybdenum, and manganese, but did not alter blood levels of chromium, cobalt or nickel. Bacterial infection did not affect any of the measured micronutrients in either moth species. These results indicate that micronutrient levels in the soil, fertilizers, and biofortified crops impact the effectiveness of biological control agents in the field. This information will help scientists correctly extrapolate control measures based on field conditions such as the type of soil and crop to use an insect virus in the field.

Technical Abstract: We studied how biologically relevant trace metals (i.e., micronutrients) in the plasma of larvae of Heliothis virescens and Helicoverpa zea (Lepidoptera: Noctuidae) changed in response to per os baculovirus infection, larval development, and injection of heat-killed bacteria. Concentrations of plasma Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, and Zn were measured using inductively coupled plasma-mass spectrometry. H. virescens larvae exhibited greater fluctuations in plasma trace metal levels in response to baculovirus infection and development than did H. zea larvae. H. zea single nucleopolyhedrosis virus infection significantly altered the levels of Cu, Fe, Mg, Mn, Mo, and Zn in 4th instar H. virescens larvae. Conversely in 5th instar H. virescens and both H. zea instar infections, no metal levels were significantly different between infected and uninfected larvae. In 4th instar H. virescens plasma, all metal levels changed during development except Ni. Cu, Fe, Mg, Mn, Mo, and Zn levels changed significantly during development in 5th instar H. virescens as well as both H. zea instars. Based on this analysis, metals were identified whose levels changed during development in both species and during the immune response of H. virescens larvae.