Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 133-139). Also available via the Internet.

The objectives of this research were to evaluate management options for tobacco thrips, Frankliniella fusca (Hinds), and reniform nematode, Rotylenchulus reniformis (Linford & Oliverira), in cotton productions systems. When evaluating tillage practices for pest control, conservational tillage reduced thrips densities and damage, while the impact on nematode densities is less understood and in this study had no impact. Insecticide seed treatments remain a vital resource for controlling thrips in Mid-South cotton production systems. When incorporating an early season herbicide application for weed control, systems with an insecticide seed treatment generally tolerated herbicide injury better than those with early season stress from thrips and nematodes. When using foliar applications as an alternative option for thrips management, early season automatic applications at the cotyledon stage followed by one or two sequential applications provided similar efficacy to the insecticide seed treatment. For reniform nematode management, 1, 3-dichloropropene reduced densities lower than that of the untreated control or aldicarb; however, depending on environmental conditions this practice may not result in yield increases great enough to warrant the cost of application. These data highlight the importance of effective control of thrips whether it be via at-planting or foliar applications. 1, 3-dichloropropene reduced nematode densities and is an effective option in nematode management; however, nematodes are a stress pathogen and the ability to minimize other seasonal stresses ,such as water stress, will determine if a nematicide application may be needed. While environmental conditions may be optimal to allow for plant recoverability, effective early season pest management decreases the potential for delayed crop maturity which could lead to increased input cost or reduced yield later in the season.

Rainfastness of insecticides is an understudied aspect of agricultural research. Little is known about the residual of commonly used products for key pests of cotton, as well as their residual after a rainfall event. This project was designed to evaluate the impact of rainfall on the performance of commonly used insecticides for tobacco thrips, Frankliniella fusca (Hinds); tarnished plant bug, Lygus lineolaris (Palisot de Beauvois); and bollworm, Helicoverpa zea (Boddie), management in cotton. Laboratory and field experiments suggest that rainfall occurring within 16 hours after application had a negative impact on the performance of most insecticides. Chemical analyses of leaf tissue using a mass spectrometer confirmed what was observed with field and laboratory experiments. Although direct comparisons between insecticides cannot be made, results from this study suggest that spinosyns and insect growth regulators appeared to have the longest residual after a rainfall event.

Research was conducted 2014-2016 to determine how tobacco thrips (Frankliniella fusca) (Hinds) resistance to neonicotinoid insecticides impact thrips resistance to neonicotinoid insecticides in cotton, Gossypium hirsutum (L.).Studies included bioassays to determine severity and mechanism of resistance and evaluation of host plant characteristics in multiple cotton varieties. Another aspect of research focused on the neonicotinoid insecticide clothianidin and its leaching ability as a seed treatment on corn by evaluating soil type, water regime, and amount found in tissue.

One of the objectives of this research was to evaluate the need for an additional imidacloprid seed treatment on ThryvOn® (Bayer Crop Science®, St. Louis, MO) cotton to effectively manage tobacco thrips, Frankliniella fusca (Hinds). While evaluating thrips densities and damage ratings, ThryvOn cotton continued to display reduced damage and thrips populations than non-ThryvOn. Thrips populations and damage ratings were consistently reduced when incorporating a higher rate of imidacloprid, but they were not reduced enough to justify the higher rates of imidacloprid. Another objective of this research was to evaluate the impact of aldicarb (AgLogic Chemical®, LLC; Chapel Hill, NC) and ThryvOn on reniform nematode, Rotylenchulus reniformis (Linford & Oliveira). The impact of aldicarb and ThryvOn technology had no impact on reniform nematode densities in Mississippi cotton throughout this study. The reduced thrips populations and damage ratings provided by ThryvOn cotton has the potential to improve integrated pest management in the southern U.S.

The immigration, population dynamics and intra-field movement patterns of the tobacco thrips, Frankliniel/a fusca (Hinds), in peanuts were studied in 1990 and 1991 in the City of Suffolk, Virginia. The long-term goal was to improve our understanding of the role of tobacco thrips in the epidemiology of tomato spotted wilt virus in peanuts; the short-term goal was to develop quantitative descriptions of thrips development and movement for inclusion in a systems model intra-field movement patterns were assessed by establishing an isolated population of thrips in the center of a (67 m2) peanut field and monitoring the subsequent spread of thrips throughout the field. Thrips did not redistribute step-wise, as expected. Instead, thrips dispersed evenly throughout the field. However, failure to observe step-wise movement was probably due at least in part to the failure of insecticides to control the thrips in the corner areas of the experimental fields. Immigration and inter-field movement of adults were monitored with sticky traps. Thrips were caught on these traps only during the immigration period, which ended approximately two weeks after plant emergence. The spatial pattern of thrips immigration indicated that their movement was strongly influenced by wind direction and also by field borders. Proximity to fields planted the previous year in peanut also apparently influenced immigration. A computer model was developed based on previous and recent laboratory studies to simulate the phenology of the tobacco thrips as a function of temperature. The model was validated using field data from the 1991 season and used to help explain apparent anomalies in the 1990 data. The model confirmed that thrips damage to peanut was caused by two generations (F1 and F2) during June and July. Model results also suggested that rainfall was a significant mortality factor in thrips population dynamics. A second model was developed to simulate thrips movement in relation to wind speed and direction. This model will be used in future studies to test hypotheses about the ability of thrips to move within and between fields. / Master of Science