Document Type

Thesis - University Access Only

Award Date

2005

Degree Name

Master of Science (MS)

Department / School

Plant Science

Abstract

Soybean aphid (Aphis glycines Matsumura) is an invasive soybean pest first discovered in the United States in 2000. The soybean aphid's arrival prompted a demand for research conducted in the United States to improve the undemanding of this insect. In August 2001, the soybean aphid was discovered in South Dakota The objectives of these studies were to measure soybean aphid reproductive potential in South Dakota and determine the effect of soybean aphid injury on soybean growth, development, and yield. Aphid infestations at two soybean development stages (VS (five trifoliate leaves on main stem) and R2 (full bloom)) and six initial aphid population treatments (0, 10, 50, and 100 aphids/plant (treatments of I and 3 aphids/plant were added in 2004)) were monitored during the 2003 and 2004 growing seasons. Comparisons across soybean development stage at infestation and initial aphid population treatments were made on measures of aphid population dynamics (lag and accelerated population growth, maximum rate of population change, peak population, and total days to reach peak population) which were determined using logistic and normal curves. Comparisons across soybean development stage at infestation and initial aphid population treatments were made on quantitative measurements of plant physiological characteristics [(leaf area index (LAI), leaf chlorophyll content (SPAD)J, and infrared canopy temperature) in non-infested and infested soybean. Soybean were grown to maturity at which point soybean yield and yield components (plant biomass, number of pods/plant, number of seeds/plant, 100 seed weight, percent seed protein, and percent seed oil) were compared to soybean development stage at infestation and initial soybean aphid population treatments. Soybean aphid populations lagged in growth for a short amount of time after V 5 and R2 soybean development infestations. Larger initial aphid population caused aphid populations to accelerate and exponentially grow sooner than lesser initial aphid populations. The total number of days that exponential population growth occurs was not significantly impacted by initial aphid population or soybean development stage at infestation. Peak aphid population was greater and occurred sooner when initial infestation populations were larger and started at V5 compared to R2 soybean development LAI and SP AD values were reduced and canopy temperatures increased with greater initial aphid population, especially in V5 infested soybean. Soybean yield and yield components were all reduced with exception of percent seed protein which increased with greater initial aphid population and earlier infestation time. These results suggest that early control of soybean aphid populations before they begin to exponentially grow is recommended to improve the efficiency of plant physiology and increase yield.

Library of Congress Subject Headings

Soybean - Diseases and pests - South Dakota
Aphids - South Dakota

Format

application/pdf

Number of Pages

195

Publisher

South Dakota State University

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