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A gronomy J our n al • Volume 10 0 , I s sue 2 • 2 0 0 8 237 , electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Accurate prediction of the level of yield loss caused by aphid feeding is considered to be the crux of integrated pest management for aphid pests (Kieckhefer et al., 1995). 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 soybean 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 (V5) and reproductive (R2) development stage. ABSTRACT Information that describes soybean aphid (Aphis glycines Matsumura) feeding injury eff ects on soybean [Glycine max (L.) Merr.] yield and seed composition is needed to develop better management practices for this invasive pest. Th is 2-yr controlled-infestation fi eld study measured aphid populations and the eff ects of those populations on soybean seed yield, yield components (shoot biomass, pods plant -1 , seeds pod -1 , and 100 seed 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 21,000, 18,000, and 12,000 aphids plant -1 and maximum cumulative aphid-days of 381,000, 327,000, and 242,000, respectively. In 2004, initial infestation rates of 1, 3, 10, 50, or 100 aphids plant -1 applied at V5 resulted in population peaks of 4,600, 9,400, 14,000, 22,000, and 21,000 aphids plant -1 and maximum cumulative aphiddays of 101,000, 229,000, 355,000, 514,000, and 537,000. 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 concentration declined linearly as peak aphid numbers plant -1 and maximum cumulative aphiddays 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 pest management treatments.

A procedure for calculating the economic injury levels for stable flies, Stomoxys calcitrans (L.), on feeder heifers was developed from reduction of average daily weight gain-stable fly population level data in 8 independent replicated experiments over 17 yr. A negative exponential was fitted to the data using nonlinear regression. Regression coefficients were then used to derive a simple predictive equation for calculating the economic injury level in relation to cost of controlling stable flies in the feedlot, and the market value of heifers. Examples for calculating the economic injury level under practical feedlot situations are presented. Also included are recommendations for a simple random sampling design for stable flies in feedlots.

Stage-specifi c economic injury levels (EILs) form the basis of integrated pest management for soybean aphid (Aphis glycines Matsumura) in soybean [Glycine max (L.) Merr.]. Experimental objectives were to develop a procedure for calculating EILs of the soybean aphid specifi c to the R2 (full bloom), R4 (full pod), and R5 (beginning seed) soybean development stages using the law of the diminishing increment regression model. Soybean aphid population growth over time appeared to follow the symmetrical bell-shaped and logistic growth curve models. Peak soybean aphid population levels and rates of increase occurred at the R5 development stage and then declined sharply thereaft er. Highest peak soybean aphid populations were 21,626 aphids plant -1 for infestations starting at V5, and 6446 aphids plant -1 for infestations starting at R2. Highest maximum aphid-days plant -1 recorded were 537,217 for V5-introduced soybean aphids and 148,609 aphid-days plant -1 for R2-introduced soybean aphids. On average, the calculated maximum possible yield loss was 75% for soybean aphid infestations starting at the V5 (fi ve node) stage and 48% for soybean aphid infestations starting at the R2 stage. Interrelationships among the current or predicted market value of soybean, cost of soybean aphid control, and the yield potential of the soybean fi eld were considered in the calculations of the stage-specifi c EILs. Practical examples for calculating stage-specifi c EILs are presented. Economic injury levels were calculated both as soybean aphids plant -1 and soybean aphid-days plant -1 . Use of these stage-specifi c EILs may enable growers to manage soybean aphids more accurately.