The two‑spot cotton leafhopper (Amrasca biguttula) has emerged as a new and invasive pest in the southeastern United States. Researchers have quickly studied its biology and lifecycle and developed management guidelines for growers faced with this new arrival in their fields. (Photo by Julien Karnoub via iNaturalist, CC BY-NC 4.0)

By Muhammad Z. “Zee” Ahmed, Ph.D.

Muhammad Z. “Zee” Ahmed, Ph.D.

Invasive species continue to place increasing demands on agricultural and regulatory systems nationwide, simply because the number of new detections has risen steadily in recent years. Like many regions experiencing high introduction pressure, the southeastern United States is working to stay ahead of this growing workload through strong partnerships among researchers, extension personnel, and regulatory agencies. Our program contributes to this broader effort by developing coordinated, science‑based tools that help ensure emerging pests are quickly recognized and effectively managed.

As part of this broader trend, the two‑spot cotton leafhopper (Amrasca biguttula) has emerged as a new and invasive pest in the southeastern United States, prompting growers and extension personnel to seek rapid, science‑based guidance. Our program’s involvement with the two‑spot cotton leafhopper began in August 2025, when growers contacted us about unexplained damage on hibiscus plants that had been pulled from production and rejected for sale. When we visited the nursery, we immediately found high leafhopper densities on these isolated hibiscus blocks, plants that had been set aside because they were “not looking right.” After we confirmed the identity of this invasive species, the grower told us directly, “Take these plants with you and find a solution for this pest.”

The two‑spot cotton leafhopper (Amrasca biguttula) is approximately 5 millimeters in length, shown alongside a pencil eraser (5 mm) and a United States penny (20 mm). (Image by Muhammad Z. “Zee” Ahmed, Ph.D., Clemson University)

We transported the infested hibiscus to my lab at Clemson University’s Pee Dee Research and Education Center in Florence, South Carolina, where they became the foundation of our colony, our early diagnostic work, and ultimately the rapid‑response framework we have been building ever since. In many ways, this grower‑driven request marked the beginning of our two‑spot cotton leafhopper program’s responsibility to stakeholders across the region, shaping the urgency and direction of everything that followed. From that point forward, our ornamental entomology work has centered on assembling the early bricks of a rapid‑response framework for two‑spot cotton leafhopper, work still very much in progress.

Early Warning and First National Alert

Our program’s first step was to alert the ornamental industry through a national field guide published in GrowerTalks on November 28, 2025. This article provided the first United States extension summary of two‑spot cotton leafhopper biology, cold tolerance, host range, and early insecticide screening results in ornamental entomology. It also offered practical scouting guidance and IRAC‑based rotation strategies at a time when ornamental growers had no information about the pest. This early alert was made possible through intensive biological observations and preliminary insecticide data generated by our research team under tight timelines. This publication became the first brick in the framework we would build.

This field guide summarizes key identification, biology, scouting, and management information for the two‑spot cotton leafhopper (Amrasca biguttula). (Image by Muhammad Z. “Zee” Ahmed, Ph.D., Clemson University)

Multi‑State Survey and Global Genetic Analysis

Immediately after the field guide, our program conducted a multi‑state survey across the southeastern United States and integrated those samples into a global phylogeographic dataset. We released the preprint on December 31, 2025, and the peer‑reviewed version was published in the Journal of Applied Entomology on January 26, 2026. This analysis revealed that all U.S. populations belonged to a single mtCOI haplotype (Hap01), confirming a single introduction event from the globally dominant lineage. No cryptic species or host‑associated divergence was detected. This genetic clarity provided the biological foundation for national management and became the second brick in our framework.

Illustrated here are the laboratory workflow, morphology, and global genetic structure of the two‑spot cotton leafhopper (Amrasca biguttula). In the upper left, an adult two‑spot cotton leafhopper is shown with size reference (a). In the photo at left, master’s student Nisha Yadav processes two‑spot cotton leafhopper samples for downstream genetic analysis at Clemson University’s Pee Dee Research and Education Center, reflecting the extensive laboratory effort behind this work (b). Yadav is an author of two peer‑reviewed publications on two‑spot cotton leafhopper and a co‑author on an additional research article and an extension publication. The graphic at right outlines steps in genetic analysis: DNA extraction and COI amplification workflow used to generate high‑quality mitochondrial sequences for haplotype confirmation (c). Mitochondrial COI haplotype diversity showing the 70 global haplotypes recovered from the curated 373‑sequence dataset (d). Global phylogeography of COI haplotypes across eight countries, illustrating the dominance of Hap01 in the United States and China and the higher diversity in South Asia, the putative native range (e). Maximum‑likelihood phylogeny of COI haplotypes demonstrating monophyly of two‑spot cotton leafhopper and the placement of 70 haplotypes relative to outgroup taxa (f). (Image originally published in Ahmed et al. 2026, Journal of Applied Entomology)

Building a Regional Network and Launching a Unified Information Platform

A defining strength of our two‑spot cotton leafhopper program is the multi‑state, cross‑disciplinary team that has come together to build the first coordinated response to this invasive pest across the Southeast. Because two‑spot cotton leafhopper affects ornamental, vegetable, and cotton systems, the working group was intentionally structured to span all three sectors and all major production regions, bringing together collaborators from South Carolina, Georgia, Florida, Alabama, Virginia, Tennessee, Texas, and federal agencies. The program is led by me as project director, supported by co‑project directors Tom Bilbo, Ph.D., for vegetables and Jeremy K. Greene, Ph.D., and Francis P.F. Reay‑Jones, Ph.D., for cotton.

To formalize and strengthen this regional coordination, the team secured a Southern IPM Working Group grant titled “A Multi‑State Working Group: Cross‑Disciplinary Collaboration for Two‑Spot Cotton Leafhopper Extension and Management,“ which supports convening university, federal, and industry partners to finalize shared tools and best practices and to launch Stop2SCL.org in partnership with the Bugwood Center for Invasive Species and Ecosystem Health. As part of this ongoing coordination, the Working Group will convene its next meeting via Zoom on April 20, 2026. (Contact the author if interested to attend.) This platform will serve as the centralized home, providing stakeholders with a single, mobile-friendly site for real-time information and management updates. Together, these coordinated efforts form the third brick in our developing TSCL response framework.

Nursery‑Pad Field Trials: Real‑World Management Tools

To provide ornamental growers with practical solutions, our program conducted the first U.S. nursery pad field trial on hibiscus, which was published in Arthropod Management Tests on March 24, 2026. This study evaluated multiple IRAC groups under real nursery conditions and identified Hachi Hachi and Safari as the strongest performers, with Altus and Ventigra also providing sustained suppression. The trial validated a two-spray, 28-day program that aligns with the pre-shipping window during regulatory inspections. This field validation became the fourth brick in our framework.

Peilin Tan, a Ph.D. student, collects count data for two‑spot cotton leafhopper during a chemical control trial on hibiscus in late fall 2025 at Clemson University’s Pee Dee Research and Education Center, reflecting the sustained field commitment behind this work. Tan is a co‑author on two peer‑reviewed publications and one extension publication on two‑spot cotton leafhopper. (Photo by Raman Mohanpuria, Clemson University)

Laboratory Bioassays: Mechanistic Understanding of Toxicity

Also on March 24, 2026, our program published the first standardized laboratory insecticide bioassay for two‑spot cotton leafhopper in Insects. This study quantified acute and residual toxicity, life‑stage susceptibility differences, and dose‑dependent mortality for key chemistries. The results provided mechanistic support for field recommendations and offered regulators the first controlled data on two‑spot cotton leafhopper insecticide performance. This laboratory foundation became the fifth brick in our framework.

Public Outreach Through the Blooms & Beyond Podcast

Recognizing the need for broader communication, our program participated in a Blooms & Beyond podcast episode titled “The Two‑Spotted Cotton Leafhopper: An Urgent Conversation with Clemson’s Entomologists“ in spring 2026. Joined by regional collaborators, we expanded awareness to growers, landscapers, extension agents, and industry partners across the Southeast. This outreach became the sixth brick in our framework.

Establishing a Permanent Scientific Platform

To consolidate global knowledge and create a long‑term scholarly foundation, our program was invited to serve as guest editor for the Insects special issue titled “Invasive Two‑Spot Cotton Leafhopper: Biology, Ecology, and Management.“ This special issue brings together research on two‑spot cotton leafhopper biology, ecology, diagnostics, management, and invasion pathways, establishing the first permanent scientific platform dedicated to this pest. This became the seventh brick in our framework.

A National Response Effort Now in Federal Review

As two‑spot cotton leafhopper spread across cotton, vegetable, and ornamental systems, early evidence showed that single‑sector projects could not address a biologically uniform pest expressed across industries with different management tools, production practices, and regulatory contexts. Because two‑spot cotton leafhopper moves freely among shared hosts and plant materials and its biology and management data are inherently cross‑applicable, a coordinated framework is essential to generate unified information and avoid duplicating overlapping efforts across commodities.

Ornamental work demonstrated that hibiscus and related hosts can sustain two‑spot cotton leafhopper for long periods, creating reservoirs that drive early‑season reinfestation into production fields. These patterns, combined with severe yield‑loss potential documented in the pest’s native range, underscore two‑spot cotton leafhopper as a multisector threat requiring a unified, science‑based response.

A Complete Framework for Invasive Species Response

From August 2025 through early 2026, our program has built a multi‑layered response to two‑spot cotton leafhopper, beginning with early detection and a grower alert, advancing through genetic confirmation, laboratory diagnostics, and the development of chemical control tools, expanding into regional coordination, and culminating in grower outreach and scholarly consolidation.

Each step filled a critical gap in the southeastern United States’ invasive‑species infrastructure and together created a rapid, coordinated model for managing emerging pests. This progress was driven by multistate collaborators, research staff, students, extension partners, and industry stakeholders whose combined expertise enabled us to meet demanding timelines and scientific standards.

Taken together, these eight foundational bricks demonstrate how a coordinated, cross‑commodity framework can be built in real time and offer a practical, transferable foundation for stronger, faster responses to future invasive species.

Muhammad Z. “Zee” Ahmed, Ph.D., is an assistant professor of turf and ornamental entomology at Clemson University’s PeeDee Research and Education Center in Florence, South Carolina. Email: [email protected].