Cotton (Gossypium hirsutum L.), is cultivated in the United States, primarily in regions characterized by long, hot summers to optimize plant growth. Virginia is the northernmost state where cotton is grown, with approximately 84,000 acres annually. The unique challenges of cultivating cotton in Virginia stems from its relatively short season due to its geographical location, lack of large contiguous acreage, and distinctive issues with pests. A significant pest of this region is the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), which emerged as a major threat to mid-Atlantic cotton during the late 2010s. L. lineolaris utilize a variety of wild and cultivated hosts to survive the winter months. The overwintering success and distribution of diapause survival L. lineolaris was measured on cover crops and weeds common in the Mid-Atlantic. Densities varied between weed and cultivated hosts, with L. lineolaris exhibiting increased survival in legumes compared to grains. Carbohydrate, lipid and protein levels were measured within diapausing and non-diapausing L. lineolaris specimens. Overwintering specimens usually had elevated level of carbohydrates and lipids, while containing decreased concentrations of protein. Nutrient quantification provided an effective tool in selecting for diapause status in L. lineolaris. Through the results from this study, an alternative method to dissection for determining diapause status in L. lineolaris has been identified. In the spring, movement of L. lineolaris throughout the landscape is highly dependent on host senesce. Flight analysis, behavioral assays and nutritional quantification assays on L. lineolaris populations from different weed hosts were performed to assess the flight capacity of specimens fed from different hosts. While weed hosts type provided populations with differing internal nutrient levels, sustained flight was not different between populations. When dispersal of L. lineolaris into cotton occurs, insecticide treatments following scouting are often necessary to prevent economic damage to the plant. Insecticide experiments were conducted aiming to assess the impact of different active ingredients on L. lineolaris, secondary pests, and natural enemy populations. Findings indicated that insecticides used to control L. lineolaris were successful at lowering pest populations and acephate was found to impact natural enemy populations. Plots applied with acephate experienced secondary pest outbreaks, highlighting the crucial role of natural enemies. / Doctor of Philosophy / Cotton is cultivated throughout the southern United States, extending up the east coast and into North Carolina and Virginia. Virginia poses unique challenges for cotton growers due to specific pest issues and need for region-specific research. The tarnished plant bug is a key pest of mid-summer cotton across this region. Overwintering studies were conducted to investigate host preferences on cover crop and weed hosts, as well as diapause survival and termination timing on cover crops. These studies revealed that hairy vetch and deadnettle species may harbor larger populations compared to other weed hosts, and that cover crops such as hairy vetch and crimson clove led to greater overwintering survival compared to grains. During diapause, metabolic changes occur that can lead to increased fat body to aid in overwintering survival. Diapausing and non-diapausing tarnished plant bugs were used in assays to quantify differences in the nutrients commonly found in this fat body. This study successfully found differences in carbohydrates, lipids and proteins levels between the diapausing and non-diapausing populations. This may allow for the identification of reproductive status of tarnished plant bugs based on nutrient levels. Flight capacity, activity levels and nutrient levels in tarnished plant bug populations taken from spring and summer weed hosts were investigated, with the objective to understand the ability of these populations to transition to cotton in the mid-summer. There were some indicators that flight initiation may be influenced by weed host, while all populations had similar flight potentials. Once in cotton, tarnished plant bugs are primarily treated with chemical insecticides which may produce unknown consequences to the system as a whole. Experiments were conducted to assess the impact of insecticides on non-target species within cotton were conducted in the field. Certain insecticides were identified to be harmful to non-target and potentially beneficial insect species, which contributed to outbreaks of other secondary pest species.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/119228 |
| Date | 03 June 2024 |
| Creators | Schepis, John Philip |
| Contributors | Entomology, Del Pozo-Valdivia, Alejandro, Schuerch, Roger, Taylor, Sally Vann, Gross, Aaron Donald, Reisig, Dominic Duane |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/pdf |
| Rights | Creative Commons Attribution-ShareAlike 4.0 International, http://creativecommons.org/licenses/by-sa/4.0/ |
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