Author: Igor Sulzbacher Schardong

The South Carolina Cotton Grower Meeting will be next week, on January 27th.

Among the topics discussed related to cotton production, the two-spot cotton leafhopper will be one of the highlights. This invasive species has worried growers in the southeast since its arrival last season.

The event will take place at the Santee Conference Center, 1737 Bass Drive/US-15, Santee, 29142.

Registration opens at 8:15 a.m., with the program beginning at 9 and concludes at 2pm.

For more information, contact Clemson’s extension cotton specialist, Mike Jones (majones@clemson.edu), or see the event announcement.

More than 80% of field corn grown in the U.S. has been genetically engineered to express one or more insecticidal toxins from Bacillus thuringiensis, called Bt toxins. Bt corn was first commercialized in the U.S. in 1996, expressing a single Bt toxin to control the European corn borer. Newer Bt corn hybrids express two or more Bt toxins, which has increased the number of target pests to include the corn earworm and the fall armyworm. Benefits of planting Bt corn can include protecting yield from insect damage, reducing the need to use insecticide, and improved grain quality. However, such benefits can be impacted by the development of resistance in target insects.

Funded by a grant from the South Carolina Corn Board, Drs. Francis Reay-Jones (Clemson Pee Dee REC, Florence, SC) and Michael Plumblee (Clemon Edisto REC, Blackville, SC) conducted field trials in 2025 to evaluate the efficacy of Bt traits and the impact Bt toxins have on the survival of corn earworm, with implications on resistance development. Trials were planted in Florence on 14 April and on 25 June, and in Blackville on 17 April. The following Bt products were used, in addition to non-Bt hybrids from the same hybrid families:

At the whorl stage, corn can sometimes be infested with fall armyworm, as was the case in May 2025 in the trial in Blackville (Figure 1). While an average of 4% of plants were infested in a non-Bt corn hybrid, no larvae were found in any of the Bt hybrids tested. In Florence, fall armyworm infestations were found only in the late planted trial, with a range of 14-28% plants infested in the non-Bt hybrids. Again, no Bt plants were infested, underlining the efficacy of Bt corn in South Carolina with this insect.

Dr. Reay-Jones has been conducting field efficacy trials with a range of Bt corn traits since 2009. Since then, some traits have become less effective over time because corn earworm has developed resistance. We saw in particular a shift in 2015 when resistance to some of the Cry toxins expressed in Bt corn became more widespread not just in South Carolina, but across the southeastern U.S. In 2025, only hybrids expressing Vip3A provided excellent levels of control. As an example of the data collected in the early planted trial in Florence, Bt traits without Vip3A provided either no suppression or limited suppression of kernel injury (Figure 2).

Survival of corn earworm was determined by placing corn ears with large larvae in plastic boxes with soil, which were then sifted to collect cocoons or pupae. A total of 282 and 717 pupae were collected in 2025 in early and late planted corn, respectively, in Florence. Pupal weights were generally lower in Bt than in non-Bt corn. No pupa was collected from corn expressing Vip3A. Pupae from Optimium Intrasect had similar weights to non-Bt corn, suggesting limited impacts on the insect. Pupae from VT Double Pro were significantly lighter than on non-Bt corn, suggesting sublethal effects that may play a role in insect resistance management.

Yields did not vary among Bt and non-Bt traits in both early and late trials in Florence. In Blackville, yield of P1366YHR (144.4 bu/ac) was significantly greater than P1366R (122.9 bu/ac), with an intermediate yield for P1366VYHR (130.6 bu/ac). While insect pressure was light in these trials, the value of planting Bt corn for growers in the southeast is due to its ability to suppress damage from a range of potential target pests, which are generally minor pests or are less common than for instance corn earworm. Although corn earworm is generally not a significant economic pest of field corn, the same species is a serious pest in cotton, where it is known as bollworm. Because Bt cotton expresses the same or similar toxins as Bt corn, selection for resistance in Bt corn is likely driving resistance issues to Bt cotton. While Vip3A remains effective, reports of unexpected injury in recent years in the mid-south underline the need for continued resistance monitoring. Vip3A toxins are also expressed in new Bt cotton varieties, and planting of non-Bt refuge in corn is crucial, since only a single Bt toxin is currently available with very good activity for this key pest. Continued monitoring of efficacy of Bt corn in field trials is important to detect potential changes in susceptibility to Bt toxins among key pests, in order to provide timely recommendations to growers in South Carolina.

The two-spot cotton leafhopper is spreading fast across the Southeast, threatening hibiscus and other ornamentals with hopperburn damage.

At Clemson’s Pee Dee REC, Dr. Zee Ahmed, along with his graduate students Nisha Yadav and Peilin Tan and research specialist Shawn Chandler, tested six insecticides, providing growers with the first science-based guidance for managing this pest in hibiscus nursery production.

Key grower takeaways:

1. Scout regularly with a 10x–30x lens

2. Match treatments to insect life stages

3. Rotate insecticides by IRAC group

4. Integrate biological & cultural controls

Figure 1: Field guide to the TSCL showing approximate adult size, life cycle stages and timing, key identification feature of two dark wing spots, common feeding damage symptoms, host plant range, scouting methods, and cultural/chemical control options.

Figure 2: Scan the QR code to access the complete field guide for TSCL, along with additional field guides on ornamental pests.

Read More: https://news.clemson.edu/clemson-launches-first-chemical-trial-to-combat-invasive-leafhopper-in-ornamentals/”

Cotton insect pests caused an estimated $798 million in yield losses plus management costs in the US in 2024. Many insects can cause damage to cotton, including the bollworm, stink bugs, thrips, and tarnished plant bugs (Figure 1).

Figure 1. Cotton pests, the brown stink bug (A, Russ Ottens, University of Georgia, Bugwood.org), tarnish plant bug (B, John C. French Sr., Retired, Universities: Auburn, GA, Clemson and U of MO, Bugwood.org), cotton bollworm (C, Gyorgy Csoka, Hungary Forest Research Institute, Bugwood.org) and thrips (D, Jack T. Reed, Mississippi State University, Bugwood.org).

As cotton pest management changed over the years, so did the importance of these pests. For example, before the introduction of cotton plants expressing Bacillus thuringiensis (Bt), cotton bollworm caused severe yield losses, leading growers to spray insecticides several times over the season to control this pest. Nowadays, with the widespread use of cotton cultivars expressing Bt toxins, yield losses and insecticide sprays to control bollworm significantly decreased.

Entomologists at Clemson University, represented by Dr. Reay Jones, Dr. Greene and the student Igor Schardong, collaborating with cotton entomologists from North Carolina, Virigina, Georgia, Alabama, Florida, and Oklahoma are distributing a survey about cotton pest management targeting growers, consultants and extension agents. The goal of the survey is to document current insect pest status in cotton, its management strategies in the southeastern states and the implementation of IPM in the Southeast US.

If you are a grower, extension personnel and consultant who grow or monitor cotton fields, please help us responding to the survey scanning the following QR code. It is important to mention that the survey is anonymous, it only takes a couple of minutes.

Figure 2. QR code to access the cotton pest management survey.

Clemson University appreciate you taking your time to help on this important matter!

Amrasca bigutulla, commonly know as the two-spot cotton leafhopper, has been detected in several states in the southeastern US, including Alabama, Georgia, Florida, and South Carolina. This species is native to southeast Asia, where it is an important pest of cotton and okra. The arrival of the insect in the continental U.S. is a concern for cotton and vegetable production, although its impact on yield remains unclear. 

Adults are characterized by two black dots on the distal part of the forewings. Females oviposit on leaf tissues, and upon hatching, nymphs grow through four developmental stages in about 8 or 9 days. Adults live an additional 11 or 12 days. The short life cycle enables two  -spot cotton leafhoppers to produce multiple generations throughout the season.

Figure 1. Adults and nymphs of  two-spot cotton leafhopper feeding under cotton leaves. 

Both nymphs and adults feed on the underside of cotton leaves by injecting its mouth part in the tissue and consuming plants sap (Figure 2). Feeding can cause the cotton leaves to turn yellow. The detection of two-spot cotton leafhoppers is a concern for cotton production in the southeastern US. In addition to quantifying potential impacts on yield, future research will focus on monitoring two-spot cotton leafhopper populations throughout the season, developing economic thresholds and treatment recommendations to provide management solutions for cotton growers.

Figure 2. Mild (left) and severe (right) injury of two-spot cotton leafhopper in cotton.  

In greenhouse, nursery, and ornamental crop production, anticipating pest threats is crucial to protecting plant health, maintaining market access, and ensuring operational efficiency. The 2026 Insecticide, Miticide & Fungicide (IMF) Guide provides an updated, science-based framework for pest management, including chemical class charts, resistance management strategies, and pest-specific recommendations. It reinforces Integrated Pest Management (IPM) principles, accurate identification, consistent monitoring, cultural and biological controls, and strategic chemical rotations to reduce resistance risk, preserve beneficial organisms, and maintain compliance with state and federal regulations.
A complete guide is available here: 2026 Insecticide, Miticide & Fungicide Guide.

This year, Dr. Zee Ahmed, Assistant Professor of Turf and Ornamental Entomology at Clemson University, took proactive pest management a step further with the release of a specialized field guide on Thrips parvispinus, a pest still under regulatory concern in the United States. Designed for growers, inspectors, and extension agents, the guide equips stakeholders with tools to detect infestations early, before they escalate into costly outbreaks. Early detection not only minimizes unnecessary insecticide applications but also slows the development of resistance and helps avoid potential trade or quarantine complications.

Together, the 2026 IMF Guide and Dr. Ahmed’s field guide form a powerful one-two punch: a comprehensive management framework paired with a targeted diagnostic tool. For stakeholders, this means better decision-making, reduced chemical dependency, and a stronger position in meeting both production and regulatory demands, assuring healthier crops, healthier markets, and a healthier future for the industry.

Figure 1. Field Guide for Thrips parvispinus (Ahmed, 2025): A visual diagnostic reference to aid in proactive detection in ornamental and edible crops.

The spotted lanternfly (SLF) has been established in 19 U.S. states since its first detection in Pennsylvania in 2014. It was confirmed in North Carolina in 2022, Tennessee in 2023, Georgia in 2024 and South Carolina in 2025. While other neighboring states in the southeastern U.S. don’t yet have confirmed established populations, the risk of establishment remains high.

Dr. Zee Ahmed (Clemson University) and his colleagues—Dr.   Shimat Joseph (University of Georgia), Dr. Midhula Gireesh (University of Tennessee), Karla Addesso (Tennessee State University) and Alejandro Del Pozo-Valdivia (Virginia Tech) developed a management calendar to support early detection and proactive control efforts for ornamental growers in the Southeastern U.S. This seasonal framework offers practical guidance to help growers address SLF concerns proactively from late summer 2025 through summer 2026.

Here is the link  Spotted Lanternfly Management Calendar for Ornamental Growers in the Southeastern U.S.

Dr. Zee Ahmed (Clemson University) and Dr. JC Chong (SePRO Corporation) have co-authored a new article in the July 2025 issue of GrowerTalks, offering practical strategies for managing scale insects in nurseries and landscapes.

Key highlights include:

• Identifying the most common scale insects
• Understanding why the crawler stage is the most vulnerable and effective target for control
• Monitoring crawler emergence using sticky bands
• Selecting insecticides that minimize impact on beneficial insects

With over 1,100 species in North America, scale insects are often difficult to detect and manage. This guide helps growers improve treatment timing and reduce long-term infestations.

Read the full article: “Target Scale Insect Crawlers to Prevent Sticky Situations” (https://www.growertalks.com/Article/?articleid=27527) in GrowerTalks, July 31, 2025.

Figure 1: Comparison of different types of scale insects

Figure 2: Top 35 scale insect species on ornamental plants: voltinism and approximate crawler emergence timing

August offers an early opportunity to help reduce next spring’s Spotted Lanternfly hatch in South Carolina. Adult populations are active now and, based on current predictions, are beginning to lay egg masses earlier than in northern states. These eggs can overwinter and hatch next spring, and they’re notoriously tricky to spot and remove once laid. Reducing the number of adults now can make a meaningful difference.

In landscapes, watch for lanternflies feeding on Tree of Heaven, grapevines, maples, and ornamental plants such as roses, lilacs, willows, birch, and blueberries. Both red-bodied nymphs and adults are present this time of year, so scout broadly: trunks, outdoor furniture, vehicles, fence posts—anywhere they might gather or lay eggs.

If you find them, remove them. Where feasible, eliminate host plants like Tree of Heaven, and consider targeted insecticide use if populations are high and egg-laying has begun. We’ve included a life stage calendar and size guide to help with identification in the field.

Don’t hesitate to contact Dr. Zee Ahmed’s team or the Department of Plant Industry at Clemson if you need assistance with identifying stages or weighing treatment options. The goal is to reduce overwintering eggs before they become next year’s problem. Refer to the included flyer for details on lifecycle timing and the activity calendar.

The Pee Dee Research and Education Center invites you to learn the most recently findings of research in plant pathology, entomology, soil and crop science in South Carolina.

Come join us in the field day organized at the Pee Dee Rec Field day on August 28th, from 9:00 am to 12:00 pm, and hear from the experts of Clemson university!