Riedell W.E.,U.S. Department of Agriculture |
Beckendorf E.A.,U.S. Department of Agriculture |
Catangui M.A.,47153 S. Clubhouse Road
Arthropod-Plant Interactions | Year: 2013
Defining the relationships between soybean (Glycine max [L.] merr.) shoot nitrogen (N) components and soybean aphid (Aphis glycines Matsumura) populations will increase understanding of the biology of this important insect pest. In this 2-year field study, caged soybean plants were infested with soybean aphids (initial infestation of 0, 10, 50, or 100 aphids plant-1) at the fifth node developmental stage. Soybean aphid populations, soybean shoot dry weight, and shoot concentrations of nitrate-N, ureide-N, and total N were measured starting at full bloom through full seed soybean development stages. Soybean aphid population as well as shoot concentration of ureide-N increased rapidly starting at full bloom, peaked at beginning seed, and dramatically decreased by full seed soybean reproductive stages. Regression analysis indicated significant relationships (P = 0.01; r = 0.71) between soybean aphid populations and shoot ureide-N concentration. Thus, soybean aphid population levels appear to coincide with shoot ureide-N concentrations in the soybean plant. © 2013 Springer Science+Business Media Dordrecht (ouside the USA).
Fausti S.W.,South Dakota State University |
McDonald T.M.,Purdue University |
Lundgren J.G.,U.S. Department of Agriculture |
Li J.,Miami University Ohio |
And 2 more authors.
Renewable Agriculture and Food Systems | Year: 2012
South Dakota has been a leading adopter of genetically modified organism (GM) crops since their introduction in 1996. In 2009, South Dakota shared the top adoption rate with Iowa for the percentage of acres planted with Bt corn. However; South Dakota has also recently experienced a significant increase in the proportion of acres treated with insecticide. The empirical evidence presented suggests that corn, hay and sunflower production in South Dakota have experienced an intensification of insecticide use in 2007 relative to past US Census of Agriculture reporting years. This study links the proportion of acres planted for a specific crop to the proportion of total acres treated with insecticide at the county level. This approach provides insight on how changing cropping patterns in South Dakota have influenced insecticide use. Empirical results indicate that the upper-bound estimate for insecticide usage on non-Bt corn acreage increased from 38% in 2002 to all non-Bt corn acres planted in 2007. The implication of this result is that in 2007 South Dakota producers were likely treating a percentage of their Bt corn acres with insecticide. Changing cropping patterns in South Dakota are also compared to that in other states in the US Corn Belt region. It appears that the South Dakota experience is not unique and is part of a broader trend. © Cambridge University Press 2011.