About

Guy Collins is a Professor and Cotton Extension Specialist in the Department of Crop and Soil Sciences at NC State University. His research focuses on cotton production and management, including cotton growth, development, and yield, particularly under high thrips pressure. He is involved in extension activities related to cotton and other crops, providing expertise and guidance to improve crop management practices. Collins has contributed to the field through numerous publications on topics such as planting patterns, pest management, seed treatment, and fertilizer optimization, supporting sustainable and efficient crop production in North Carolina.

Research topics

• Agronomy
• Biology
• Horticulture
• Chemistry
• Ecology

Selected publications

• Soybean growth habit influence on development, yield, and seed quality in North Carolina full‐season soybean production

  Agronomy Journal · 2026-03-01

  articleOpen access

  Abstract North Carolina soybean [ Glycine max (L.) Merr.] production has historically relied on later maturing determinate varieties, but recent availability of later maturing indeterminate varieties has raised questions about growth habit effects on soybean production in the region. This study evaluated the impact of soybean growth habit (indeterminate versus determinate) within maturity group V on soybean plant height, nodes, lodging, green stem, yield, and seed quality across nine environments over 2 years (2023–2024). Trials were conducted using five determinate and five indeterminate varieties planted between late April and early May. Indeterminate varieties exhibited greater height and node count at maturity. However, growth habit alone did not consistently influence final yield or seed quality outcomes across environments. In over 50% of environments, there was no impact of soybean growth habit on yield, while in two environments indeterminate varieties were higher yielding and in two environments determinate varieties were higher yielding. Indeterminate varieties had greater green stem, lodging, seed oil, purple seed stain, and seed damage. These results provide foundational agronomic information for producers to make data‐driven decisions based on growth habit.

  PublisherDOI

• Evaluating selected skip‐row planting patterns for upland cotton ( <i>Gossypium hirsutum L</i> .) in North Carolina

  Agronomy Journal · 2026-03-01

  articleOpen access

  Abstract Input costs associated with cotton ( Gossypium hirsutum L .) production systems have increased exponentially in recent years, prompting interest for innovative cost‐saving methods, such as alternative row configurations. The objective of this study was to evaluate the ability of various skip‐row systems to achieve similar, or greater, net returns to that of conventionally planted cotton without row skips across multiple years and environments in North Carolina. The alternative row configurations evaluated were a four and one skip‐row, a two and one skip‐row, and an ultra‐wide‐row (UWR) that were then compared to solid‐planted cotton without skips. Net returns for each configuration were developed using recent economic data and a range of potential lint valuations. Field studies were conducted from 2021 to 2024 at several research stations in Eastern North Carolina, totaling 17 site‐years. The 2 × 1 and UWR configurations generally yielded significantly lower net returns than solid‐planted cotton in all years except 2023 when accounting for seed and harvest costs, suggesting limited utility in North Carolina cotton production. In 2024, the 4 × 1 configuration netted a greater return than solid‐planted cotton at a lint price of $1.433 kg −1 when accounting for seed and harvest costs, but similar returns should be expected from these two systems in most years. These results suggest that the 4 × 1 skip‐row system in NC may occasionally yield greater net returns than conventionally planted cotton when lint prices are relatively low, after accounting for savings on planting seed and harvest operation costs.

  PublisherDOI

• Cotton growth, development, and yield when utilizing ThryvOn under high thrips pressure

  Agronomy Journal · 2026-03-01

  article

  Abstract Thrips (Thysanoptera: Thripidae) are consistent pests in cotton ( Gossypium hirsutum ) production during the early season. In addition to cultural and chemical practices for thrips management, a new Bt ( Bacillus thuringiensis ) trait called ThryvOn is available for thrips management. However, research investigating crop development and yield response to this new technology is limited. Therefore, a field trial was implemented in Tifton, GA, USA, to evaluate thrips prevalence, plant injury, crop development, and lint yield in response to cultivar (with or without ThryvOn) and insecticide treatment under high thrips pressure. ThryvOn cotton exhibited lower thrips densities and plant injury due to thrips than non‐ThryvOn cotton, regardless of insecticide treatment. When interactions between cultivar and insecticide were observed, insecticide treatment reduced pest pressure and positively impacted plant growth to a larger extent in non‐ThryvOn cotton compared to ThryvOn cotton. Similar observations were made for radiation capture by the crop canopy, although significant effects were only observed on one sample date in a single growing season. Lint yields were not affected by cultivar or insecticide treatment in either year, despite significant plant injury in the early season. The data from this study further highlight that newly available ThryvOn varieties offer significant thrips injury protection relative to non‐ThryvOn varieties, decreasing the need for insecticide application. Thrips injury and reductions in plant growth in the early season may not necessarily translate to yield loss if radiation capture by the crop canopy is eventually maximized and there is sufficient growing season length available to mature the crop.

  PublisherDOI

• Fungicide seed treatment impact on soybean stand and yield across planting dates and maturity groups in North Carolina

  Agronomy Journal · 2025-07-01

  articleOpen access

  Abstract Producers across the state of North Carolina are planting soybean at earlier planting dates as a mechanism to increase yield, and as a result, questions arise regarding whether fungicide seed treatments are needed at earlier planting dates to protect soybean stand and yield. Experiments were conducted from 2019 to 2020 at four environments across North Carolina that were selected to represent a range of geographies and growing conditions commonly encountered in North Carolina soybean production. Planting dates evaluated included early April, mid‐ to late April, mid‐May, and mid‐June. Maturity groups evaluated included III, IV, and V. The seed treatments included in this study represent a range of the commercially available fungicide seed treatments and fluctuated between 2019 and 2020 but were compared to a nontreated control in each environment. Fungicide seed treatment impact on soybean stand was variable across environments, with stand protection from using treated seed in one environment of 12,146 plants ha −1 at the earliest planting date (early April). Soybean maturity group also impacted the value of a fungicide seed treatment, which is likely a result of differing varietal resistance packages to seedling diseases among the soybean maturity groups used in this study. Fungicide seed treatments provided considerable yield protection at planting dates in mid‐May and earlier. Results across these environments emphasize the variability in which fungicide seed treatment can protect soybean stand and yield across planting dates and environments, and producers should consider planting date and environmental conditions when making decisions about this input.

  PublisherOA PDFDOI

• Optimizing pyroxasulfone-coated fertilizer in cotton

  Weed Technology · 2025-01-01 · 1 citations

  articleOpen access

  Abstract Two studies were conducted in 2022 and 2023 near Rocky Mount and Clayton, NC, to determine the optimal granular ammonium sulfate (AMS) rate and application timing for pyroxasulfone-coated AMS. In the rate study, AMS rates included 161, 214, 267, 321, 374, 428, and 481 kg ha −1 , equivalent to 34, 45, 56, 67, 79, 90, and 101 kg N ha −1 , respectively. All rates were coated with pyroxasulfone at 118 g ai ha −1 and topdressed onto 5- to 7-leaf cotton. In the timing study, pyroxasulfone (118 g ai ha −1 ) was coated on AMS and topdressed at 321 kg ha −1 (67 kg N ha −1 ) onto 5- to 7-leaf, 9- to 11-leaf, and first bloom cotton. In both studies, weed control and cotton tolerance to pyroxasulfone-coated AMS were compared to pyroxasulfone applied POST and POST-directed. The check in both studies received non-herbicide-treated AMS (321 kg ha −1 ). Before treatment applications, all plots (including the check) were maintained weed-free with glyphosate and glufosinate. In both studies, pyroxasulfone applied POST was most injurious (8% to 16%), while pyroxasulfone-coated AMS resulted in ≤4% injury. Additionally, no differences in cotton lint yield were observed in either study. With the exception of the lowest rate of AMS (161 kg ha −1 ; 79%), all AMS rates coated with pyroxasulfone controlled Palmer amaranth ≥83%, comparably to pyroxasulfone applied POST (92%) and POST-directed (89%). In the timing study, the application method did not affect Palmer amaranth control; however, applications made at the mid- and late timings outperformed early applications. These results indicate that pyroxasulfone-coated AMS can control Palmer amaranth comparably to pyroxasulfone applied POST and POST-directed, with minimal risk of cotton injury. However, the application timing could warrant additional treatment to achieve adequate late-season weed control.

  PublisherOA PDFDOI

• Mid‐season pest management implications for protecting soybean seed quality in North Carolina

  Agronomy Journal · 2025-03-01 · 3 citations

  articleOpen access

  Abstract Soybean producers in North Carolina have shifted from later to early‐maturing varieties (MG II‐IV) to increase yield. This shift has coincided with more frequent seed damage and purple seed stain, sometimes resulting in dockage at the elevator. Weather is a major driving factor in seed quality issues, but management strategies may play a role to minimize these seed quality issues; these have not been investigated in North Carolina. To better understand the impact of pest management on seed quality, field trials were conducted over two growing seasons (2021–2022) in three environments across North Carolina. Soybean yield, seed damage, purple seed stain, protein, and oil were collected. Moreover, non‐treated controls were scouted at R3 and R5 for each planting date and maturity group combination to determine pest dynamics at each location. While fungicide applications improved yield, pesticide applications did not significantly protect seed quality compared to the untreated control. Continuous scouting and as needed pesticide application can help producers improve soybean yield and protect seed quality.

  PublisherOA PDFDOI

• Row spacing effects on soybean production in North Carolina

  Crop Forage & Turfgrass Management · 2025-03-28

  articleOpen access

  Abstract North Carolina soybean [ Glycine max (L.) Merr.] growers use a diverse range of row spacings, commonly between 7.5 and 38 inches. Research findings regarding the effect of row spacing on soybean yield have been inconsistent and influenced by factors such as planting date and environmental conditions. Although small‐plot data from North Carolina often indicates that narrower row spacings lead to higher yields, growers have raised concerns about the potential benefits of wide rows when ripping is employed in environments exhibiting symptoms of subsurface compaction. Research was conducted over 2 years (2021–2022) in the Coastal Plain region to evaluate the effects of wide row ripped spacing (36 or 38 inches) compared to un‐ripped narrower spacing (15 inches) on plant population, canopy cover, soil compaction, and yield across four environments. One of the environments included an additional treatment with an un‐ripped drilled row spacing of 7.5 inches. Although seeding rates were calibrated similarly, the ripped wide‐row spacing treatments led to lower achieved plant population, predominantly due to adverse seed bed conditions resulting in lower germination caused by the inline ripper. The un‐ripped narrow row spacings (7.5 and 15 inches) consistently demonstrated 7–25% greater canopy cover than ripped wider spacings (36 and 38 inches) by the flowering stage (R1). Soil penetration resistance varied by row spacing in only two environments, with differences generally lacking agronomic significance (i.e., penetration resistance &lt;2 MPa). Yield results indicated no significant effect of row spacing in three out of four environments; in the fourth environment, the un‐ripped 15‐inch row spacing yielded significantly more than both the un‐ripped drilled and ripped wide‐row soybeans. In the environments in this study, wide‐row ripped treatments offered no agronomical advantage over narrow row un‐ripped treatments.

  PublisherOA PDFDOI

• Adjusting seeding rate across soybean planting date and maturity in the Southeast United States

  Crop Science · 2025-03-01 · 2 citations

  articleOpen access

  Abstract Soybeans [ Glycine max (L.) Merr.] are planted across a wide range of planting dates (PDs) (March to early August) in the Southeast United States, resulting in a wide range of growing conditions and, consequently, soybean production practices used. Current seeding rate (SR) recommendations should be revisited to reflect the range of PDs and other management practices used in the Southeast United States. Studies were conducted across 15 North Carolina environments from 2019 to 2022 to determine the agronomically optimal seeding rate (AOSR) and economically optimal seeding rate (EOSR) required for the PDs and maturity groups (MGs) used by soybean producers in the Southeast United States. Main plot treatments included PD (mid‐March through mid‐July), sub‐plot included MGs (2–7), and sub‐subplot included SR (185,329–432,434 seeds ha −1 ). Early PDs generally resulted in lower plant populations due to environmental conditions such as cooler soil temperatures. Higher SRs resulted in higher plant populations across environments. PD, MG, and SR interacted to impact soybean yield ( p = 0.02) and revenue ( p = 0.02). Earlier PDs, March to April 10 (day of year [DOY] 80–100), resulted in lower yields and revenues compared to a more moderate full‐season PD, April 30–May 20 (DOY 120–140), and delayed planting required higher AOSR and EOSR to maximize yield and revenue. Variations in MGs also impacted optimal SRs, with MGs (2–4) generally requiring higher AOSR and EOSR than MGs (5–8). AOSR and EOSR analyses reveal a positive correlation between SR, yield, and revenue up to a certain threshold, beyond which increasing SR does not significantly improve yield or revenue. Soybean producers should adjust their SR based on PD and MG selection.

  PublisherOA PDFDOI

• Residual weed control in cotton utilizing herbicide-coated fertilizer

  Weed Technology · 2024-11-19 · 1 citations

  articleOpen access

  Abstract An experiment was conducted in 2022 and 2023 near Rocky Mount and Clayton, NC, to evaluate residual herbicide-coated fertilizer for cotton tolerance and Palmer amaranth control. Treatments included acetochlor, atrazine, dimethenamid- P , diuron, flumioxazin, fluometuron, fluridone, fomesafen, linuron, metribuzin, pendimethalin, pyroxasulfone, pyroxasulfone + carfentrazone, S -metolachlor, and sulfentrazone. Each herbicide was individually coated on granular ammonium sulfate (AMS) and top-dressed at 321 kg ha −1 (67 kg N ha −1 ) onto 5- to 7-leaf cotton. The check plots received the equivalent rate of nonherbicide-treated AMS. Before top-dress, all plots (including the check) were treated with glyphosate and glufosinate to control previously emerged weeds. All herbicides except metribuzin resulted in transient cotton injury. Cotton response to metribuzin varied by year and location. In 2022, metribuzin caused 11% to 39% and 8% to 17% injury at the Clayton and Rocky Mount locations, respectively. In 2023, metribuzin caused 13% to 32% injury at Clayton and 73% to 84% injury at Rocky Mount. Pyroxasulfone (91%), pyroxasulfone + carfentrazone (89%), fomesafen (87%), fluridone (86%), flumioxazin (86%), and atrazine (85%) controlled Palmer amaranth ≥85%. Pendimethalin and fluometuron were the least effective treatments, resulting in 58% and 62% control, respectively. As anticipated, early season metribuzin injury translated into yield loss; plots treated with metribuzin yielded 640 kg ha −1 and were comparable to yields after linuron (790 kg ha −1 ) was used. These findings suggest that with the exception of metribuzin, residual herbicides coated onto AMS may be suitable and effective in cotton production, providing growers with additional modes of action for late-season control of multiple herbicide–resistant Palmer amaranth.

  PublisherOA PDFDOI

• Soybean stand and yield impact from a fungicide seed treatment in North Carolina soybean production

  Crop Forage & Turfgrass Management · 2024-09-14

  articleOpen access

  Abstract North Carolina soybean [ Glycine max (L.) Merr.] producers have shifted to earlier planting dates as a mechanism to increase soybean yields. As growers have shifted to earlier planting dates, soybean fungicide seed treatment use has become more common. In 2020 and 2021, on‐farm research investigated the value of a fungicide seed treatment across the state. Experiments were conducted across 18 diverse production environments in North Carolina during that time. Treatments included fungicide seed treatment (fludioxonil: 2.32%, mefenoxam: 13.9%, and sedaxane: 2.32%, i.e., Vibrance Trio, a commonly used multi‐mode of action fungicide across the state and country) compared to untreated seed. Data collected included soybean stand and soybean yield. The use of a fungicide seed treatment variably affected stand, but when combined over environments, fungicide seed treated plots averaged 110,757 plants/acre as opposed to untreated plots averaging 101,570 plants/acre with significant stand protection in seven of 18 environments. When averaged across environments, fungicide seed treatment protected yield by 1.3 bu/acre which, depending on input practices and soybean selling price, would border providing a return on investment. As planting date was delayed past mid‐April, yield decreased for both fungicide treated and untreated plots. Results from this trial indicate that fungicide seed treatments can provide protection of soybean yield and stand in North Carolina although protection provided may not provide a return on investment with current input prices.

  PublisherOA PDFDOI

Frequent coauthors

• Keith L. Edmisten

  North Carolina State University

  82 shared

• Seth A. Byrd

  73 shared

• Jared R. Whitaker

  50 shared

• John L. Snider

  University of Georgia

  45 shared

• Gaylon D. Morgan

  Cotton (United States)

  39 shared

• Darrin M. Dodds

  39 shared

• Tyson B. Raper

  University of Tennessee at Knoxville

  37 shared

• Randy Norton

  University of Arizona

  37 shared

Labs

• Crop and Soil SciencesPI