Author
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Hesler, Louis |
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BERG, ROBERT - SOUTH DAKOTA STATE UNIV |
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Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/4/2003 Publication Date: 12/1/2003 Citation: Hesler, L.S., Berg, R.K. 2003. Tillage impacts cereal-aphid (Homoptera: aphididae)infestations in spring small grains. Journal of Economic Entomology 96(6): 1792-1797. Interpretive Summary: It is difficult to predict how preplant tillage might affect insect pests, like cereal aphids, that colonize small-grain crops after emergence. We compared cereal-aphid levels in spring-seeded wheat and barley grown with and without preplant tillage for eight different combinations of locations and years in eastern South Dakota. Crop residue covered about 25 percent of the soil surface with preplant tillage, whereas without preplant tillage 50 percent or more of surface residue was conserved. Bird cherry-oat aphids comprised nearly 90 percent of all cereal aphids sampled, and corn leaf aphids, greenbugs and English grain aphids collectively comprised the remainder. Bird cherry-oat aphids routinely infested lower parts of tillers and were generally concealed by surface residue in plots with no preplant tillage. Overall, bird cherry-oat aphids were more abundant in plots with no preplant tillage, although in comparisons at individual sites they were greater in no-preplant tillage plots only once. For all cereal-aphid species combined, infestations were only greater in plots with no preplant tillage at one location in one year. Cereal aphids were never more abundant in plots with preplant tillage. Our results show that conservation tillage leads to greater infestations of bird cherry-oat aphids in spring small grains, as increased surface residue provides a favorable microhabitat for this aphid species. Technical Abstract: It is difficult to predict how preplant tillage might affect insect pests, like cereal aphids, that colonize small-grain crops after emergence. We compared cereal-aphid levels in spring-seeded wheat and barley grown with and without preplant tillage for eight site-years in eastern South Dakota. Crop residue covered about 25 percent of the soil surface with preplant tillage, whereas without preplant tillage 50 percent or more of surface residue was conserved. Rhopalosiphum padi (L.) comprised nearly 90 percent of all cereal aphids sampled, and R. maidis (Fitch), Schizaphis graminum (Rondani) and Sitobion avenae (F.) collectively comprised the remainder. Rhopalosiphum padi routinely infested lower parts of tillers and were generally concealed by surface residue in plots with no preplant tillage. Across seven site-years, R. padi were more abundant in plots with no preplant tillage than with preplant tillage (170.1 +/- 37.2 versus 272.6 +/- 54.4 aphid-days per 25 tillers). However, in comparisons at individual site-years R. padi were greater in no-preplant tillage plots only once. For all cereal-aphid species combined, infestations were greater in plots with no preplant tillage for one of eight site-years, but did not differ with tillage when compared across all site-years. Cereal aphids were never more abundant in plots with preplant tillage. Our results show that conservation tillage leads to greater infestations of R. padi in spring small grains, as increased surface residue provides a favorable microhabitat for this aphid. |
