Agronomy and Horticulture, Department of


First Advisor

Loren J. Gielser

Second Advisor

Gary Y. Yuen

Date of this Version


Document Type



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agronomy, Under the Supervision of Professors Loren J. Giesler and Gary Y. Yuen, Lincoln, Nebraska: December, 2016

Copyright 2016 Kelsie M. Musil


The soybean cyst nematode (SCN, Heterodera glycines) is the most yield limiting pathogen of soybeans (Glycine max L. Merr.). Current management strategies of crop rotation and using resistant varieties are not completely effective and alternative management strategies are needed. Commercial seed treatments with biological agents are available to protect against yield loss from SCN, but have not been evaluated in Nebraska. Field studies were conducted in eight Nebraska locations (six infested with SCN and two non-infested) during 2014 and 2015 to evaluate seed treatment effects on soybean establishment, SCN population density, and yield. The seed treatments were CruiserMaxx® Advanced, Clariva®Complete Beans containing Clariva®pn (Pasteuria nishizawae), and Poncho®/ VOTiVO® containing Bacillus firmus I-1582; all treatments contained the same fungicides and an insecticide with the same mode of action. Average yields in the SCN infested fields ranged from 45 to 72 bu/A and initial SCN population densities ranged from 200 to 4,300 eggs/100 cc’s of soil. No statistical differences were found among the three treatments in either yield or SCN reproduction at any individual location or when the SCN infested locations were combined in either growing season. The use of cover crops (cereal rye, Secale cereale), and other bacteria have inconsistently reduced SCN populations in previous studies. The use a cover crop as a means to establish a biocontrol agent has not been investigated. Greenhouse experiments were conducted to evaluate the ability of the bacterium Lysobacter enzymogenes C3 to colonize the rhizospheres of cereal rye and soybean from populations applied to seed. The bacterium was found to colonize cereal rye roots to higher population levels than soybean over 4 week periods. C3 root populations on cereal rye increased by a thousand fold from seed populations. Based on these studies the potential for biocontrol for SCN exists, but more research is needed to determine optimum conditions for biocontrol agents to be effective tools in sustainable soybean production.

Advisors: Loren J. Giesler and Gary Y. Yuen

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