Date of Award

12-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Division of Agriculture (SAFES)

Committee Member

Jeremy K. Greene, Committee Chair

Committee Member

Francis P.F. Reay-Jones, Committee Co-Chair

Committee Member

Alana L. Jacobson

Committee Member

Phillip M. Roberts

Abstract

Thysanoptera (Haliday), or thrips, are minute, polyphagous insects known globally for their role as crop pests. One species important economically to South Carolina and the southeastern United States is the tobacco thrips, Frankliniella fusca (Hinds). This species is the most predictable pest of upland cotton, Gossypium hirstutum (L.). Thrips are particularly damaging to cotton when they infest seedling cotton. In some years, tobacco thrips are recorded as the most detrimental pest of cotton in terms yield loss. Yield loss from tobacco thrips infestations varies widely between years and even within the same year. By analyzing agricultural control practices, an accurate window of infestation can be found. Understanding when tobacco thrips infestations occur gives farmers an idea of the risk they may incur for a given planting date. Cotton farmers need more accurate risk projections for tobacco thrips infestations to combat infesting thrips populations with reduced sensitivity to neonicotinoid class insecticides. Cultural control practices are needed to help mitigate tobacco thrips management problems associated with reduced sensitivities to chemicals. Two potential cultural control practices for tobacco thrips are planting date and host plant resistance. Planting date and choice of variety mitigate injury from F. fusca infestations in cotton. A planting date study was conducted in Blackville, South Carolina, using a mid-full maturing variety in 2015, an early maturing variety in 2016, and both an early maturing and a mid-full maturing variety in 2017. In every year, cotton planted after mid-May suffered significantly lower thrips densities and subsequent injury from thrips. A variety study was also conducted in 2016 and 2017 in seven sites across the Southern United States with varieties PHY 312, PHY 333, PHY 444, PHY 499, DP 1646, DP 1410, DP 1538, ST 4747, ST 4946, ST 6182, and FM1900. ST 4946, a variety with a consistently larger seed size, generally had larger dry weights and less injury than other varieties despite having a similar amount of thrips infesting it. A significant correlation was found in the study between cotton plant seed size and weight compared to cotton plant dry weight and cotton plant height. The information reported in these studies can aid cotton farmers from a risk management perspective to make the best decision for their thrips prone fields manage thrips in cotton.

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