Trophic interactions between three species of cereal aphid (Hemiptera: Aphididae) and spring wheat (Poaceae): implications for pest management

Abstract

The susceptibilities of genetically diverse Canadian spring wheats, Triticum aestivum L. and Triticum durum Desf., to three aphid species, Rhopalosiphum padi (L.), Sitobion avenae (Fabricius), and Schizaphis graminum (Rondani), were investigated. Trophic interactions measured as changes in biomass of aphids and wheat plants were used to quantify levels of resistance, components of resistance, and impact of aphids on yield. Plants in field cages were infested with small numbers of aphids for 21 days at heading. These plants were usually more suitable for the development of S. avenae and S. graminum than of R. padi. Partial resistance, measured as seed production by infested plants as a proportion of that by a control, varied from 11% to 59% for different aphid species and wheat classes when all wheat plants were infested at the same stage. Cultivars within wheat classes responded similarly to each of the aphid species. None of the wheat cultivars showed agriculturally effective levels of antibiosis. The specific impact of each aphid species and wheat class varied from 5 to 15 mg of plant biomass lost for each milligram of biomass gained by the aphids. Canadian Western Red Spring wheat had a lower specific impact and therefore was more tolerant to aphids than the other two classes, but not tolerant enough to avoid economic damage at the aphid densities observed. Plants did not compensate for feeding damage after aphid feeding ceased, based on the higher specific impacts observed for mature plants than for plants that were heading. The interactions between aphids and plants show that current economic thresholds probably underestimate the damage caused by cereal aphids to Canadian spring wheat.

Herbivore identity mediates the strength of trophic cascades on individual plants

“…M. viciae affects the plant far less (but still enough to record a clear trophic cascade), despite greater abundance and similar body weight (Sutter, unpublished data). A similar difference in ratio of plant biomass lost to aphid biomass gained has been found among aphid species on cereals (Migui and Lamb 2007). Some species appear to be characterized by a boom and bust strategy whereby colonies grow fast and overexploit their host plant individual while other species appear to follow a more prudent strategy that avoids over-exploitation and death of the host plant.…”

Plant-insect interactions in changing environments

“…According to our results, parasitoid spillover from cropland may significantly influence trophic cascades in wild habitats, which is rarely shown, but should be widespread shaping natural food webs. (Holland and Thomas 1997;Matson et al 1997;Migui and Lamb 2007). Agricultural management such as intercropping compared to monocultural planting and fertilization has been shown to affect yield in agroecosystems (Theunissen 1994;Praslicka and Mistina 2004;Zehnder and Hunter 2008).…”