Date of Award

8-2014

Document Type

Thesis

College

College of Arts and Sciences

Degree Program

Biology

Degree Name

Master of Science

Abstract

The southern green stink bug, Nezara viridula (L.), is a detrimental crop pest in the southern states of the USA. Soybean, Glycine max (L.) Merrill, is a major economic crop that receives extensive damage from N. viridula. Damage includes decreases in crop yield and germination as well as damaged beans. Continued research is needed to understand feeding behaviors of N. viridula. Electronic Penetration Graph (EPG) monitoring is a valuable resource for observing and measuring the feeding behavior of numerous species of hemipterans.

This study was conducted to observe and characterize waveform patterns in the feeding behavior of N. viridula on G. max. Three waveform families, A, B, and C, were identified in this research. Within the waveform family B, two types, B1 and B2, were further identified. Waveforms of the family A highly resemble pathway and salivation waveforms found in studies of other heteropterans. Waveforms of type B1 highly resemble ingestion from xylem tissue and vascular bundles found in studies of hemipteran species. Correlation trials found stylet sheaths that terminated in xylem tissue created during a B1 waveform event. Waveform type B2 was found only when insects were feeding on soybean pods at the R3 and R5 developmental stage. No B2 type waveforms were ever found on vegetative potted plants or excised petioles, only on pods, suggesting that this waveform represents ingestion of endosperm tissue.

Identified waveforms were used to compare two methods for presenting host plants in EPG research. Insects were allowed to probe on the petioles of potted plants and excised tissue. Waveforms were virtually identical between the two treatments. Insects on potted plants did have an overall higher duration of time spent probing, but there were no differences in the duration of individual probes or individual waveforms.

Identified waveforms were also used to compare the probing behavior of N. viridula on G. max across three developmental stages. Insects were allowed to probe on excised petioles and on small R3 pods and large R5 pods attached to excised stems. Overall, insects were more active on both the R3 and R5 pods when compared to petioles. Insects on R3 pods had more short duration probes than other insects that did not include a B waveform event, suggesting that they are frequently failing to locate preferred tissue on these small pods, and actively searching for a food source of high nutritional value.

This study successfully identified waveforms for N. viridula on G. max. These waveforms were also successfully used to compare feeding behavior across several developmental stages of G. max and between potted vegetative plants and excised petioles. Identified waveforms will be valuable for future research to correlate each with specific probing behavior and target tissue. Waveforms will also be valuable for comparison with other heteropteran insects and perhaps to screen soybean genotypes and varieties for resistance to heteropteran pests.

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