Doctoral Dissertations

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Plants, Soils, and Insects

Major Professor

Annette Wszelaki

Committee Members

Bonnie Ownley, Juan Luis Jurat-Fuentes, David Butler


Organic growers are limited in crop protection techniques for cucumber beetle management. Spotted (Diabrotica undecimpunctata howardi) and striped (Acalymma vitatta) cucumber beetles and are significant pests of cucurbits in the U.S. Feeding results in aesthetic damage and reduction in marketable yields as well as transmission of bacterial wilt that can result in plant mortality. Biopesticides are products formulated from naturally occurring organisms such as fungi and bacteria that are pathogenic or toxic to insect pests. Advantages to these products are that they have low environmental risk, low risk to non-target organisms including mammals and beneficial insects, and can help reduce resistance to pesticides when used in an integrated pest management program. The overall goal of this dissertation was to examine the potential of microbial products to reduce mortality and feeding by cucumber beetles for the benefit of organic producers. Chapter one is a review of the biopesticide industry, biology of microbial agents for insect pest management, the role of biopesticides in sustainable agriculture, and constraints to their use. Chapter two is on the field experiment conducted on Galia melons in 2010 and 2011 using Chromobacterium subtsugae and Beauveria bassiana. Chapter three is on the laboratory assays using Beauveria bassiana and the laboratory and field experiments using Isaria fumosorosea. Chapter four is the final experiment on the effects of these microbial agents on cucumber beetles and squash bugs in organic pumpkin production. The results indicated anti-feedant effects by Chromobacterium subtsugae and Beaveria bassiana in the laboratory assays, but field trial results were inconclusive and did not show a reduction in beetle populations or a yield increase resulting from spray applications of these microbial agents. Complications in the field studies arose from plant pathogens and physiological factors independent from cucumber beetle population and damage. Recommendations are to improve biopesticide efficacy through improving formulation and delivery, by additional screening and testing to determine efficacy on multiple life stages of the pest, and research to increase the understanding of ecological roles and interactions of microbial biopesticides in the environment.

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