Date of Award

8-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Entomology

Committee Member

Dr. Francis Reay-Jones, Committee Chair

Committee Member

Dr. Jeremy Greene, Committee Chair

Committee Member

Dr. Eric Benson

Committee Member

Dr. Paula Mitchell

Committee Member

Dr. Michael Toews

Abstract

Megacopta cribraria (Fabricius) (Hemiptera: Plataspidae) has spread through thirteen states and the District of Columbia since accidental introduction into the United States in 2009. The potential impacts to soybean production necessitated research into the ecology and management of the plataspid in its new invasive range. A two year study in South Carolina using sweep-net and beat-cloth sampling generated sampling plans for M. cribraria population estimates and sequential sampling plans for pest management decision making. At all adult and nymph densities fewer sweep net samples were required for population estimations compared with the number of beat cloth samples. Sequential sampling reduced the sample size required to reach a management decision for both sampling methods compared with a fixed sampling plan. The sweep net method was more cost reliable for population estimation at low densities of both life stages; the beat cloth became more cost reliable as populations increased. The beat cloth method was more cost reliable than sweep-net sampling across all densities and life stages for pest management practices. White cross-vane traps as a sweep-net sampling alternative on soybean were evaluated. Adults were first collected in traps before the sweep net. Adults collected from trap and sweep-net sampling decreased from the field edge towards the field interior. There was a positive association between the two sampling methods, but only 36% of weekly, by location analyses were significantly correlated. Collected females were rated based on egg development. Female populations of all reproductive maturities dispersed into soybean but proportions varied with sampling method. Kudzu, Pueraria montana Loureiro (Merrill) variety lobata (Willdenow) plays an important role in the bivoltine life cycle of M. cribraria so sweep-net sampling was employed to monitor seasonal activity over three time periods, in two kudzu patches in South Carolina. Adults colonized kudzu in early April and were present until October. The majority of females were intermediate or fully reproductive in early spring, whereas non-reproductive females dominated as the season progressed. Soybean stem-feeding behavior was conducted on adult females using electropenetrography and was the first time a member of the Plataspidae has been recorded using this technique. Waveforms were described and correlated with stylet insertion by staining for salivary sheaths. Adult females performed a stereotypical set of feeding behaviors and stylet sheaths terminated in vascular tissue during ingestion. Scanning electron microscopy images of M. cribraria mouthpart structures were produced and described. In 2014, nematodes were reported infecting M. cribraria adults for the first time, and were subsequently found in nymphs of M. cribraria, Euschistus servus (Say), Chinavia hilaris (Say) and adults of Euschistus spp. in 2015. Infection in less mobile nymphs suggests the insects were parasitized directly in the soybean field from which they were collected. Morphological and molecular analyses confirmed the nematode belongs to the family Mermithidae, genus Agamermis. Overall, the research presented in this dissertation presents insights into M. cribraria biology and ecology and provides information to facilitate sampling practices for improved reliability of M. cribraria estimates for research and pest management purposes. Entomoparasitic nematode infection in hemipteran pests emphasizes the need to acknowledge covert, under-studied natural enemies which may contribute to population regulation.

Share

COinS