Date of Award

5-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Entomology

Advisor

Greene, Jeremy

Committee Member

Reay-Jones, Francis

Committee Member

Benson, Eric

Committee Member

Roberts, Phillip

Committee Member

Shipe, Emerson

Abstract

Megacopta cribraria (F.) (Hemiptera: Plataspidae), known informally as the kudzu bug or bean plataspid, was found in Georgia in 2009 and has since spread rapidly throughout the southeastern United States. A known feeder on soybean, Glycine max (L.) Merrill, in its native Asian range, M. cribraria has been commonly encountered in soybean fields in the southeastern United States since its first detection in the crop in Georgia and South Carolina during 2010. In addition, its overwintering behavior sometimes results in nuisance infestations in homes. The primary objectives of this research were to determine the potential impacts of M. cribraria on soybean production, examine its spatial ecology and host preferences, and evaluate management options for agricultural and nuisance infestations. Voucher specimens of all life stages were deposited in the Clemson University Arthropod Collection in Clemson, SC. To estimate impacts on soybean yield, adults of M. cribraria were confined to small plots of soybean at densities of 0, 5, and 25 per plant, and their offspring were allowed to complete development on these plants. Yields were reduced by up to 60%, and seeds per pod and weight per seed were similarly reduced. Grid sampling of individual soybean fields during 2011-2012 revealed that M. cribraria had an aggregated spatial distribution. Densities of adults tended to be higher on the edges than in the interiors of fields. The residual activity of insecticides applied to common building materials was evaluated in a series of laboratory bioassays on adults of M. cribraria. Most of the pyrethroids tested provided nearly complete control within 24 h, particularly on non-porous surfaces. Similar results were observed in field trials evaluating insecticides labeled for use in soybean; pyrethroids such as bifenthrin and &lambda-cyhalothrin were consistently among the most effective active ingredients. Observations from the field indicated that a fungal pathogen was infecting adults and nymphs of M. cribraria in soybean, and the rate of mortality due to this pathogen increased with density of M. cribraria. This fungus was identified as Beauveria bassiana (Balsamo) Vuillemin clade A based on morphology and genomic DNA sequence alignment, and its pathogenicity was confirmed based on Koch's postulates. Common protocols were conducted in South Carolina, Georgia, and North Carolina to evaluate timing of insecticide application based on treatment thresholds and plant phenology for management of M. cribraria in soybean. A single application timed at stage R3 or R4, a treatment threshold of two adults or nymphs of M. cribraria per sweep, and a treatment threshold of one M. cribraria per sweep with nymphs present were generally cost-effective and prevented soybean yield loss. A host preference study conducted in a laboratory growth chamber showed that kudzu, Puereria montana (Loureiro) Merrill variety lobata (Montandon), and soybean were preferred for oviposition over Wisteria sinensis (Sims) de Candolle and cotton, Gossypium hirsutum L. Early-planted soybeans had high infestations in a trial evaluating the impacts of planting date and maturity group on populations of M. cribraria. Soybeans planted in late June or July had much lower densities and smaller yield reductions. The research presented in this dissertation provides critical information for the development of integrated pest management programs for this emerging invasive pest.

Included in

Entomology Commons

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