Document Type

Thesis - University Access Only

Award Date

2004

Degree Name

Master of Science (MS)

Department / School

Plant Science

First Advisor

Billy W. Fuller

Abstract

Ladybird beetles (Coleoptera: Coccinellidae) are important beneficial polyphagous predators of insect pests in maize fields. This study evaluated the impact of Cry3Bbl hybrid (corn rootworm-resistant maize) on adult abundance and life stages of coccinellids during preanthesis, anthesis, and postanthesis development of maize. Cry3Bb 1 maize expresses a protein derived from a coleopteran-specific kumamotoensis subspecies of Bacillus thuringiensis (Berliner) that was bioengineered to induce com rootworm larval mortality. Thus, this hybrid primarily targets, Diabrotica barberi Smith & Lawrence and Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), northern and western com rootworms that are two of the most injurious insect pests of maize (Zea mays L.) in the Midwestern U.S. combelt. If non-target coccinellids were found to be susceptible to this Cry3Bbl toxin, then they could potentially be negatively impacted by their omnivorous feeding or from preying on herbivorous maize insects. To assess any potential impacts from this maize hybrid on coccinellids, Pherocon AM sticky traps and whole-plant sampling methods were_ utilized near Brookings, South Dakota during 2001 and 2002. Results from sticky trap captures in Cry3Bb 1 maize, did not indicate any deleterious impacts on coccinellid adult abundance during preanthesis, anthesis, or postanthesis development of maize. For example, number of adult coccinellids captured in Cry3Bbl maize was not significantly different from those in untreated plots during preanthesis. However, during anthesis and postanthesis, coccinellid adults were more abundant in Cry3Bb 1 maize when compared with those from tefluthrin-treated and untreated plots. Additionally, similar results were found for the dominant coccinellid species Coleomegilla maculata DeGeer. This dominant coccinellid species represented 73.5 and 69.9% of the total adults captured in 2001 and 2002, respectively. Results from whole-plant sampling observations indicated a overall lack of deleterious effects on the abundance of egg, larva, pupa, and adult life stages. It could be argued that greater coccinellid conservation occurred in Cry3Bb 1 maize agroecosystem. Future use of this maize hybrid could potentially decrease insecticide use for com rootworm control; therefore, resulting in a greater abundance of beneficial arthropods within maize fields.

Library of Congress Subject Headings

Ladybugs.
Northern corn rootworm -- Control.
Western corn rootworm -- Control.
Corn -- Disease and pest resistance -- Genetic aspects
Hybrid corn.

Publisher

South Dakota State University

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Rights Statement

In Copyright