Agronomy and Horticulture, Department of

 

First Advisor

Julie A. Peterson

Second Advisor

Sydney E. Everhart

Date of this Version

8-2019

Document Type

Thesis

Citation

Ercan, Gülçin, “ Dual Biological Control: Characterization Of Fungi And Bacteria To Control Granary Weevil And Fungal Pathogens Of Stored Grain” (2019). Thesis, Dissertation and Student Research in Agronomy and Horticulture.

Comments

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 Julie A. Peterson & Sydney E. Everhart. Lincoln, Nebraska: August, 2019

Copyright 2019 Gülçin Ercan

Abstract

Cereals are main food sources for humans and animals. However, during storage, cereal grains can be infested by insects and fungi. One of the most important insect storage pests is Sitophilus granarius (L., Coleoptera: Curculionidae). Adults and larvae can cause serious grain losses. In addition to insect pests, fungal pathogens may also invade the grain and cause economic loss, including contamination with mycotoxins, which threaten mammal health by causing serious disease. The most common mycotoxigenic grain fungi are species that belong to the genera Fusarium, Aspergillus and Penicillium. Currently, the most commonly used management strategies for insect and fungal storage pests are based on conventional pesticides and cultural methods. However, there is a need for alternatives to conventional pesticides due to their side effects, insecticide resistance, and consumer demand for uncontaminated food. Cultural methods may not be cost-effective or practical in all storage facilities. Moreover, both insect and fungal pests share the same niche and have possible interactions with each other that increase economic losses. Therefore, the aim of this study was to find potential biocontrol agents that showed dual biocontrol effect against granary weevil and three common fungal pests in stored grain. We determined that two fungal isolates (Trichoderma gamsii E1032 and E1064) and one bacterial isolate (B. amyloliquefaciens C415) achieved dual control against both the insect pest and the fungal pathogens by causing mortality of S. granarius and suppression of three grain fungal pathogens. In addition, a specific aim of this study was the examination of lethal and sublethal effects on S. granarius. Metarhizium anisopliae E213 showed strong sublethal effect by reducing ovipositio rate and grain infestation additionally, Cladosporium halotolerans E126 minimally reduced oviposition rate yet was significantly different from negative control. Also, all tested bacterial treatments had significantly lower survival than the negative control. And, Bacillus thuringiensis C423 showed strong sublethal effect by reducing feeding damage and oviposition rate. Additionally, candidate biocontrol agents were tested against grain fungal pathogens with two different method, antibiosis and wheat seed bioassays, to confirm performance of the effective isolate on the real stored grain. Bacillus amyloliquefaciens, Lysobacter enzymogenes, and Burkholderia ambifaria demonstrated the highest antifungal activity. This study demonstrates dual biocontrol against insect and fungal pests, which has potential as a component of Integrated Pest Management strategies for stored grain.

Advisors: Julie A. Peterson & Sydney E. Everhart

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