The threecornered alfalfa hopper (TCAH), Spissistilus festinus (Say), is a sporadic pest in seedling cotton that has the potential to cause significant impact to cotton growth and development. Threecornered alfalfa hopper is a stem girdling pest that generally feeds on the main stem of cotton plants from the two- to eight-leaf growth stages. To better understand the potential impact of this pest on cotton growth and development, trials were conducted in Starkville and Stoneville, MS in 2023 and 2024. Experiments were implemented as a randomized complete block design with a factorial arrangement of treatments with four replications. Factor A was simulated TCAH damage at 0, 10, 20, 30, 40, and 50% increments; factor B was damage timed at the three- and six-leaf growth stage. Damage was simulated by applying low rates of glyphosate to stunt the plant to approximate TCAH damage. There were no significant impacts of simulated TCAH damage level percentage or timing on yield. Therefore, the results from this study suggest that TCAH
