Soybean Aphid Feeding Injury and Soybean Yield, Yield Components, and Seed Composition

Authors: Beckendorf, Eric; CATANGUI, MICHAEL - SOUTH DAKOTA STATE UNIV; Riedell, Walter

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/2007
Publication Date: 4/1/2008
Citation: Beckendorf, E.A., Catangui, M.A., Riedell, W.E. 2008. Soybean Aphid Feeding Injury and Soybean Yield, Yield Components, and Seed Composition. Agron. J. 100:237-246.

Interpretive Summary: The soybean aphid, which was first reported in the U.S. in 2000, was detected in 21 U.S. states and 3 Canadian provinces by 2003. Because female aphids can reproduce asexually and produce live young, this invasive pest species has the ability to increase its population logarithmically in response to favorable environments. Accurate prediction of the level of yield loss caused by aphid feeding is considered to be the crux of integrated pest management for these pests. Despite the accumulating literature on the soybean aphid, there are currently few published data on the effects of soybean aphid populations on soybean yield and seed components for soybeans grown in the United States. Thus, the objectives of this study were to quantify aphid populations and the injuries caused by those populations on plant biomass, seed yield, and components (total yield, pods plant-1, seeds pod-1, individual seed weight, oil concentration, protein concentration) in plants infested at the vegetative and reproductive development stage. Our results indicate that the reproductive potential of the soybean aphid was very high. A single aphid per plant introduced at the vegetative stage, for example, multiplied to a peak of 4627 aphids per plant and resulted in 101076 maximum cumulative aphid-days per plant. We also observed that seed yield, yield components, and seed oil percent declined linearly as peak aphid numbers per plant and maximum cumulative aphid-days per plant increased. We feel that relating these aphid population parameters at the plant growth stages studied to yield responses by this economically-important crop enables producers to make informed decisions about the need for and timing of rescue chemical treatments against the soybean aphid.

Technical Abstract: Information that describes soybean aphid (Aphis glycines Matsumura) feeding damage effects on soybean [Glycine max (L.) Merr.] yield and seed composition is needed to develop management practices for this invasive pest. This 2-yr controlled-infestation field study measured aphid populations and the effects of those populations on soybean seed yield, yield components (shoot biomass, pods plant-1, seeds pod-1, and 100 kernel weight), and seed composition (oil and protein concentrations) when infested at the vegetative (V5) or reproductive (R2) development stages. In 2003, initial infestation rates of 10, 50, or 100 aphids plant-1 applied at V5 resulted in population peaks of 21000, 18000, and 12000 aphids plant-1 and maximum cumulative aphid-days of 381000, 327000, and 242000, respectively. In 2004, initial infestation rates of 1, 3, 10, 50, or 100 aphids plant-1 applied at V5 resulted in population peaks of 4600, 9400, 14000, 22000, and 21000 aphids plant-1 and maximum cumulative aphid-days of 101000, 229000, 355000, 514000, and 537000, respectively. In both years, the same infestation rates applied at R2 resulted in population peaks and cumulative aphid-day values that were about 42 to 88 % lower than the V5 infestation dates. Seed yield, yield components, and seed oil percent declined linearly as peak aphid numbers plant-1 and maximum cumulative aphid-days plant-1 increased. In contrast, seed protein concentration increased linearly with increasing peak aphid numbers plant-1. Relating these aphid population parameters at the plant growth stages studied enables producers to make informed decisions about the need for and timing of rescue chemical treatments.