Abstract
Fresh market vegetables are an essential component of the human diet. Maximizing yield is critical, and to achieve this goal, fields must be weed-free when vegetable crops are planted. Historically, removing emerged weeds just before planting has been accomplished using the herbicide glyphosate. However, recent research has indicated that glyphosate applied to sandy, low-organic-matter soils just before transplanting vegetables can be injurious. Two field experiments investigated 1) the response of transplanted squash to the residual activity of glyphosate, and 2) the effects of implementing tillage, irrigation, or extending the plant-back interval after application and before planting to mitigate injury from glyphosate. Glyphosate applied at 1.3, 2.5, or 3.8 kg ae/ha 1 day before transplanting injured squash 13%, 29%, and 53%, respectively; extending the interval between application and planting to 7 days reduced injury to 1%, 11%, and 28% at the same rates. An interaction between application rate and planting interval was also observed on squash plant widths and biomass, as well as early-season and total marketable fruit numbers and weights. Total marketable fruit number was reduced 29% and 52% by glyphosate at 2.5 or 3.8 kg ae/ha, respectively, and a reduction in fruit production of 36%, 28%, and 23% was observed when glyphosate was applied 1, 4, or 7 days before transplanting, respectively. In a separate study, light tillage (5 cm deep) was the most effective cultural practice evaluated because it eliminated damage by glyphosate. Overhead irrigation of 0.6 cm was not beneficial in mitigating injury by glyphosate. Recommendations from this research will help vegetable growers avoid injury from the residual activity of glyphosate through a FIFRA 2(ee) recommendation label.
Georgia fresh-market vegetable production is a critical component of the state’s agricultural economy (Kane 2024; US Department of Agriculture 2023; University of Georgia, Center for Agribusiness and Economic Development 2024). Contributing more than $1.3 billion annually, 33 high-value vegetable crops are grown year-round in the state (University of Georgia, Center for Agribusiness and Economic Development 2024). As one of the top 10 vegetables produced in Georgia, yellow squash (Cucurbita pepo) was grown on more than 1640 ha in 49 counties during 2022 and had a market value of $50 million, with a 59% increase in production value from 2017 to 2022 (Stubbs 2020; University of Georgia, Center for Agribusiness and Economic Development 2020, 2022a, 2022b, 2024; Wolfe and Stubbs 2018, 2019). Approximately half of the yellow squash in the state is produced in plasticulture systems, with the remainder grown in conventional bareground systems (Coolong 2017). In a bareground system, land is prepared using tillage to remove plant debris, weedy pests, and soil clods, which facilitates ideal soil conditions for optimal root growth and helps prevent over-saturated soils through enhancing drainage (Csizinszky 2005). Additionally, while preparing the land, the soil is often treated with a fumigant to mitigate the impacts of nematodes (Chowdhury 2024; Hajihassani 2018; Kemble et al. 2024). Once the land is tilled, the plant bed has been formed, and the fumigate has dissipated, yellow squash is either seeded or transplanted. Using squash transplants allows for uniform stand establishment, promotes an earlier harvest, and increases profit and yield potentials (Olson et al. 1994; Rulevich et al. 2003; Schultheis et al. 1988).
The time interval between land preparation and planting is influenced by fumigant dissipation, weather conditions, and the availability of transplants from the greenhouse supplier. A significant amount of time may pass between land preparation and planting, during which problematic weeds can emerge because the fumigant used for controlling nematodes is ineffective at controlling weeds (Salt Lake Holding LLC 2024). When present at planting, weeds quickly out-compete vegetable crops for space, light, nutrients, water, and pollinating insects, often becoming difficult to control in-season and resulting in reduced crop quality and yield (Capinera 2005; Monks and Schultheis 1998; Trader et al. 2008; William and Warren 1975; Zimdahl 2018). Furthermore, if not managed early, weeds can become hosts for pathogens, attract insect pests, or conceal mature fruit from being identified for harvest (Randell et al. 2021; Sosnoskie et al. 2008; Starke et al. 2006; Walters et al. 2005). Therefore, preplant burndown herbicides are often used to remove weeds before planting. Vegetable crops, especially cucurbits such as summer squash, are extremely sensitive to many herbicides and their soil residues which limits options for use before and during the growing season (Culpepper et al. 2009; Grey et al. 2007a, 2007b; Wallace et al. 2012). Herbicide selection is highly dependent on the crop, cultivar, planting method, and the production system in which the crop will be produced (Culpepper et al. 2009; Dittmar et al. 2023; Fennimore and Doohan 2008; Kemble et al. 2024). Current labeled options for preplant burndown weed control before transplanting squash include glyphosate, carfentrazone, paraquat, pyraflufen, and fomesafen (FMC Corporation 2017; Nichino America 2020; Syngenta Crop Protection 2019a, 2019b). To minimize risks and potential impacts from off-target particle drift, narrow weed control spectrums, limited efficacy due to weed size, and the potential for soil residual activity and crop injury, growers commonly select glyphosate as their preplant burndown tool.
With yellow and purple nutsedge being among the most common and troublesome weeds infesting vegetable crops (VanWychen 2022), preplant applications of glyphosate at use rates up to 2.5 kg ae/ha are recommended by the product label, with sequential applications suggested (Bayer CropScience 2021). This rate of glyphosate also provides control of other common weeds such as crabgrass (Digitaria) spp., morningglory (Ipomoea) spp., purslane (Portulaca) spp., and pigweed (Amaranthus) spp. Historically, the scientific consensus was that glyphosate did not exhibit residual soil activity and therefore could be applied preplant without injury concerns to vegetable crops. Published research has indicated that the herbicide was both quickly broken down through microbial degradation and bound tightly to soil colloids (Bayer CropScience 2021; Shaner 2014). Glyphosate is an excellent option to apply for burndown weed control before planting highly sensitive vegetable crops, especially at the high use rates used for nutsedge control. However, observations of crop injury after glyphosate applied preplant to Georgia vegetables produced on sandy, low organic matter soils, indicated the glyphosate–soil residual relationship was more complex than previously thought.
Previous research has identified the ability of glyphosate residues to injure crops grown in sandy, low organic matter soils (Cornish 1992; Devlin et al. 1986; Rosenberg et al. 1988). Glyphosate’s physiochemical properties indicate its strong adsorption to soil particles; however, bioassay experiments indicate that residues from glyphosate applied preplant could injure vegetable transplants including tomato (Solanum lycopersicum), pepper (Capsicum annuum), and cucumber (Cucumis sativus) in soils with low adsorption capacities (Cornish 1992; Rosenberg et al. 1988). In these situations, researchers indicate that glyphosate is not readily absorbed to sandy soils; therefore, the herbicide remains available for plant uptake from the soil water solution. In recent years, research has documented field-level impacts of glyphosate negatively influencing growth and yield of cucurbit and fruiting vegetables when applied preplant up to 7 d before transplanting (Goodman et al. 2019; Wright-Smith et al. 2023).
Due to high costs associated with growing vegetable crops, strict market and consumer standards, and the high value of the harvested marketable product, subsequent crop injury cannot be tolerated in vegetable production systems by growers (Fennimore and Doohan 2008; Johnson and Hoyt 1999; Kunkel et al. 2008). Therefore, it is vital to have a complete understanding of the complex relationship between the residual activity of glyphosate and subsequent planting of highly sensitive vegetable crops. Of equal importance, however, is the need to develop mitigation measures that eliminate vegetable grower concern regarding injury, to preserve this preplant herbicide. Therefore, the objectives of this research were to determine 1) the tolerance of transplanted squash in conventional tillage systems to the residual activity of glyphosate, as influenced by rate, and 2) the effects of implementing additional tillage, irrigation, or a greater plant-back interval after glyphosate applications and before transplanting in mitigating crop injury.
Materials and Methods
Two experiments were each conducted twice between 2018 and 2021 at the University of Georgia Ponder Research Farm in Ty Ty, GA, USA (lat. 31.30′18°N, long. 83.39′03°W, elevation 109 m), where soils are a Tifton loamy sand (fine-loamy, kaolinitic, thermic Plinthic Kandiudult). Soil texture, organic matter, pH, and cation exchange capacity for each site year are provided in Table 1. Before study initiation, the land was prepared with tillage, and 1,3-dichloropropene (66 kg ai/ha) was shank injected into the soil profile at 36 cm deep and 91 cm wide while simultaneously forming plant beds on a 2-m spacing. After treatments specific to each experiment as defined below were implemented, the crop was planted. At planting, a tractor-mounted hole punch wheel (Kennco Manufacturing Inc., Ruskin, FL, USA) was used to punch transplant holes in a single row down the plant bed, 2 to 4 cm off the center, on a 30-cm between-plant spacing. Squash (12 cm in height with three true leaves) were immediately transplanted into the hole, and the root ball was covered with soil by hand. After planting, a single line of drip tape (Rivulis Irrigation, San Diego, CA, USA) was placed down the center of each bed, on the soil surface, to facilitate irrigation and fertilization requirements throughout the season. Drip tape had an emitter spacing of 30 cm and a flow rate of 1.5 L·m−1 (per 30 m).
Soil texture, organic matter, soil pH, cation exchange capacity, and soil type for four studies conducted from 2018 through 2021 in Ty Ty, Georgia.
All land preparation, fumigation, planting, irrigation, fertilization, and crop maintenance for insects and diseases throughout each growing season were conducted following university recommendations (Kemble et al. 2024). To remove the confounding effects of weeds, a standard herbicide program was implemented across each study. Fomesafen (140 g ai/ha) was broadcast applied preplant, with ethalfluralin (420 g ai/ha) being applied only in the row middles during the same day; S-metolachlor (530 g ai/ha) was applied broadcast topically 10 d after planting (DAP) and clethodim (90 g ai/ha) was applied topically 21 DAP (Culpepper and Singleton 2024). Any remaining weeds were removed by hand throughout the growing season before reaching heights or diameters of 5 cm.
Squash response to glyphosate as influenced by rate and application interval experiment.
To investigate crop response, the experiment was conducted twice during 2018 and 2019. The experimental design consisted of an augmented factorial arrangement of treatments, consisting of three levels of glyphosate rates and three levels of preplant application timings, arranged in a randomized complete block design; a nontreated control was also included (Hand et al. 2020; Marini 2003). For each study, plots comprised an area 2 m by 8 m and included four replications. Glyphosate was applied either 7, 4, or 1 d before planting (DBP) at 1.3, 2.5, or 3.8 kg ai/ha, using a CO2-pressurized backpack sprayer, equipped with 11002 Teejet Air Induction nozzles (Teejet Technologies, Wheaton, IL, USA) and calibrated to deliver 140 L·ha−1 at 276 kPa. Application dates and rainfall accumulation during the interval between herbicide application and planting are provided in Table 2. Approximately 24 h after the final herbicide treatment application, squash (cultivar Grand Prize in 2018 and Enterprise in 2019; Seminis, St. Louis, MO, USA) was transplanted into the field.
Squash planting date, glyphosate preplant application interval, application date, and accumulated rainfall for studies conducted during 2018 and 2019 in Ty Ty, Georgiai.
Squash response to glyphosate as influenced by tillage and overhead irrigation experiment.
Experimental design of the tillage and overhead irrigation experiment, conducted during 2020–21, consisted of a factorial arrangement of treatments that included three glyphosate rates and four mitigation tactics, arranged in a randomized complete block design. Plots comprised an area 2 m by 8 m and included four replications within each study. For the first treatment level, glyphosate was applied within 1 d of planting (3 Apr 2020 and 6 Apr 2021) at either 0, 2.5, or 5.0 kg ae/ha; rates and planting intervals were aggressive to ensure mitigation tactics could be appropriately tested. The second level included one of four cultural mitigation practices following glyphosate applications: 1) overhead irrigation, 2) light tillage, 3) overhead irrigation plus light tillage, and 4) no overhead irrigation or tillage. A nontreated control was also included. Overhead irrigation was provided by a sprinkler system delivering 0.6 cm. Light tillage was implemented through the use of a tractor-mounted rototiller (Maletti Macchine Agricole, Modena, Italy), incorporating the top 5 cm of the soil at an operating speed of 2.6 kph, with the implement set to 1800 rotations per minute.
The order of events to establish the experiment were as follows: 1) glyphosate treatments to be followed with irrigation were applied, and overhead irrigation of 0.6 cm was applied ∼4 h after application; 2) the remaining herbicide treatments were applied 1 h after the irrigation event; 3) light tillage was implemented on the appropriate plots ∼4 h following the final glyphosate application; and 4) squash (cultivar Enterprise) was transplanted into the field after tillage was completed, on 3 Apr 2020 and 6 Apr 2021. At 48 h after planting, the entire study received an additional sprinkler irrigation of 0.6 cm to ensure plants were set for ideal growth and development.
Data collection across experiments.
Beginning 7 DAP and continuing weekly until initial harvest, crop injury was accessed using a 0 (no crop injury) to 100 (complete plant death) subjective visual scale to determine the tolerance of squash to glyphosate soil residues. To quantify treatment impacts on plant growth, squash plant diameters were measured three to four times, beginning 7 DAP and continuing through the completion of injury evaluations. For each assessment, the canopy diameter of 10 consecutive plants were measured in centimeters across their widest point. Early-season fresh weight biomass was collected by removing eight plants at the soil line from one end of each plot and collectively weighing the aboveground plant material. Fresh weight biomass was only collected once during the season when crop injury was at its maximum level (17 to 28 DAP). Density was also evaluated by counting the number of plants present in each plot when collecting biomass to determine if treatments influenced plant survivability. At crop maturity, yield was assessed from 10 plants per plot for 21 to 30 harvests, which was collected 6 d weekly to mimic commercial harvesting practices. For all harvests, yield was a measure of the number of marketable fruit (well-formed and free from decay, damage, bruises, scars, and discoloration) and collective weight for each plot (US Department of Agriculture 2016).
Statistical analysis.
To account for differences in observation intervals between study years, squash plant widths and fresh weight biomass have been converted to a percentage of the nontreated control for analysis and discussion. To determine the effects of glyphosate soil residual activity following preplant applications on transplanted squash, data were assessed for normality and subjected to analysis of variance using the GLIMMIX procedure in SAS Enterprise Guide 8.3 (SAS Institute, Cary, NC, USA). Interactions between treatments and years were evaluated to determine whether data combined across studies was appropriate, and due to no significance, all data were combined over years for analysis. Study years and replication (nested within year) were included as random effects, and treatments and interactions between treatments were considered fixed effects for each experiment (Moore and Dixon 2014). For significant effects, treatment means were separated using the Tukey–Kramer least square means test (P ≤ 0.05).
Results and Discussion
Squash response to glyphosate as influenced by rate and application interval experiment.
For all response variables, data were combined over years for analysis. Injury, plant widths, and fresh weight biomass were influenced by the interaction between glyphosate rate and the time interval between the preplant application and planting (Table 3). Squash early-season and total yield was influenced by the main effects alone of glyphosate rate and preplant application timing (Table 3).
P values of main effects and interactions as influenced by glyphosate rate and application interval, for visual crop injury, squash plant width, fresh weight biomass, early-season yield, and total yield in Ty Ty, Georgiai.
Maximum visual squash injury, recorded as chlorosis/necrosis and stunting, was observed 17 DAP. Due to the high sensitivity and strict buyer standards of vegetable crops produced for the fresh market, visual crop injury greater than 10% is not tolerated by producers. Glyphosate applied 1 DBP at 1.3, 2.5, or 3.8 kg ae/ha injured squash 13%, 29%, and 53%, respectively, exceeding the injury threshold at all application rates (Table 4). Similar to research conducted by Goodman et al. (2019) on transplanted cucumber, extending the interval between application and planting to 4 d reduced injury at the aforementioned rates to 4%, 19%, and 38%, whereas an interval of 7 d further reduced injury to 1%, 11%, and 28% at the respective rates (Table 4). Following a preplant herbicide application, and during the transplanting process, a tractor-mounted mechanical hole punch is used to punch plant holes. This implement pushes the treated soil down into the newly formed plant hole as it moves across the field, creating the opportunity for the transplant root ball to contact treated soil directly, and absorb herbicide-contaminated soil water. Further contact with herbicide-treated soil can occur as soil is pulled around the plant to cover the root ball when transplanting. This is done by hand; therefore, human variability can influence the amount of herbicide the transplant contacts. In sandy soils with low organic matter, where fewer sites are available for glyphosate adsorption to soil colloids, more glyphosate is present in the soil water solution for plant absorption (Salazar and Appleby 1982; Sprankle et al. 1975). It is important to acknowledge that the potential for crop injury is more likely in this production system, where a combination of sandy low organic matter soils, a mechanical hole punch method, and hand-transplanting of the crop is used.
Squash visual injury and fresh weight biomass as influenced by glyphosate applied 1, 4, or 7 d before planting during 2018 and 2019 in Ty Ty, Georgia.
Squash plant canopy widths 21 to 28 DAP were significantly reduced 8%, 20%, and 36% from glyphosate applied at 1.3, 2.5, and 3.8 kg ae/ha respectively, compared with the nontreated control (data not reported). When combined over rate, however, squash widths were significantly reduced 15%, 18%, and 31% from glyphosate applied 1, 4, and 7 DBP (data not reported). Squash fresh weight biomass (12 to 19 DAP) followed similar trends, fresh weight biomass was reduced 23%, 52%, and 79% with a 1-d planting interval as the rate increased from 1.3, 2.5, and 3.8 kg ae/ha, respectively (Table 4). Extending the preplant application interval to 4 or 7 d minimized the impact, although glyphosate at 2.5 kg ae/ha reduced biomass 14% to 40% at these intervals, respectively, and at 3.8 kg ae/ha the reduction was 58% to 69% (Table 4). Although treatments influenced squash growth and development significantly, plant mortality was not observed (data not reported).
Timely crop maturity is critical to ensure fresh-market produce is ready to harvest and sell when market demands are high; therefore, the ability to harvest the crop as early as possible in the season is desirable. This is often the most valuable fruit, and any delay in maturity can be costly (Illic 1990). Early-season yield, representative of the first five harvests of the season, was significantly influenced by glyphosate at 2.5 and 3.8 kg ae/ha, where fruit number was reduced 46% to 75% and fruit weight was reduced 54% to 80%, at each rate respectively (Table 5). Early-season fruit number following glyphosate at the lowest application rate was not significantly different from the nontreated control, however, fruit weight was reduced 18% (Table 5). Glyphosate applied 1, 4, or 7 DBP reduced early-season fruit number and weight 35% to 41%, 44% to 51%, and 51% to 59%, respectively (Table 6). Total season yield, collected over 21 harvests, followed a similar trend as early-season yield. Combined over application timing, total fruit number was significantly reduced 29% to 52% and total fruit weight was reduced 30% to 54% from glyphosate only at the two highest rates (Table 5). When combined over rate, glyphosate reduced total fruit number and weight a minimum of 23% at all preplant application timings (Table 6).
Early-season and total marketable fruit number and weight of squash as influenced by glyphosate rate applied preplant during 2018 and 2019 in Ty Ty, Georgia.
Squash early-yield and total marketable yield, both number of fruit and total fruit weight, as influenced by glyphosate applied preplant 7, 4, or 1 d before planting during 2018 and 2019 in Ty Ty, Georgia.
Squash response to glyphosate as influenced by tillage and overhead irrigation experiment.
After confirming glyphosate applied preplant posed a significant risk to transplant squash production, a second experiment was conducted to determine whether light tillage and/or overhead irrigation could be used to mitigate the concern of crop injury from residual herbicide activity. In this experiment, all response variables, including crop injury, plant widths, fresh weight biomass, and both fruit number and fruit weight of early-season and total season yield, were influenced by a significant interaction between glyphosate rate and tillage following application (Table 7). The main effect of irrigation alone or in combination with other factors did not influence response variables, thereby confirming that implementing a single 0.6 cm of overhead sprinkler irrigation is not an effective practice to mitigate the potential residual activity of glyphosate applied just before transplanting squash.
P values of main effects and interactions as influenced by preplant glyphosate rate, tillage, and overhead irrigation for visual squash injury, plant width, fresh weight biomass, early-season and total yield in Ty Ty, Georgiai.
Maximum visual squash injury was observed 21 to 28 DAP, where 21% and 57% crop injury were recorded following glyphosate applied preplant at 2.5 and 5.0 kg ae/ha (Table 8). When light tillage was implemented after application and before planting, injury of 5% or less was observed across glyphosate rates with injury similar to that of the control. Cornish (1992) indicated that potential residual activity from glyphosate could be reduced through increased absorption after mixing of glyphosate-treated soil. Previous research conducted in broccoli and collards also documented tillage (depth of 5 cm) effectively mitigated the residual uptake of glyphosate (≤2.5 kg ae/ha) applied preplant to sandy, low-organic-matter soils (Wright-Smith et al. 2023). With glyphosate available in the soil solution after preplant applications, due to fewer adsorption sites in sandy, low-organic-matter soils, a light tillage could incorporate and dilute the herbicide concentration to levels low enough that sensitive crops such as squash are no longer at risk of crop injury.
Squash visual injury, plant widths, and fresh weight biomass as influenced by light tillage following preplant glyphosate applications, during 2020 and 2021 in Ty Ty, Georgia.
Squash plant widths, recorded 21 DAP, and early-season fresh weight biomass 17 to 25 DAP, followed similar trends to visual crop injury. Without tillage, glyphosate at 2.5 and 5.0 kg ae/ha reduced squash widths 19% and 34% and biomass 38% and 56%, respectively, compared with the nontreated control (Table 8). Implementing light tillage following glyphosate eliminated impacts to squash widths and fresh weight biomass regardless of glyphosate rate.
Early-season yield, representative of the first five harvests of the season and the ability to quickly market the crop, included both fruit number and respective weight. Glyphosate reduced squash fruit number 23% and 56% when applied at 2.5 and 5.0 kg ae/ha; fruit weight was significantly reduced 61% only at the highest application rate (Table 9). For both yield metrics, light tillage after applying glyphosate and before planting eliminated early-season yield reductions. Total season yield was evaluated over 21 to 30 harvests and followed similar trends to early-season yield. Glyphosate at 2.5 and 5.0 kg ae/ha reduced total fruit number and weights 16% to 42%, whereas, again, implementing light tillage effectively avoided yield loss.
Squash early-season and total yield, both number and weight, as influenced by tillage following preplant glyphosate applications during 2020 and 2021 in Ty Ty, Georgia.
In conclusion, glyphosate applied on sandy, low-organic-matter soil before transplanting squash can be damaging to the crop, likely a result heavily influenced by root uptake. Glyphosate application rate, time interval between application and transplanting, and tillage after application can influence the level of damage observed when applying glyphosate before transplanting sensitive vegetables. Because there is unpredictability in the amount of glyphosate available for uptake by the plant due to variability in the adsorption to soil colloids and in the transplanting process, building recommendations including each of these practices is warranted. The results of this research were used to develop a label for Georgia vegetable farmers, providing use recommendations for application rate, irrigation requirements, and interval between application and planting, to help prevent crop injury following preplant applications of glyphosate in sandy, low-organic-matter soils (Bayer CropScience 2020).
References Cited
Bayer CropScience. 2020. FIFRA 2(ee) Recommendation Roundup PowerMAX® 3 herbicide product label. https://www.cdms.net/ldat/ld0RF005.pdf. [accessed 9 Jul 2024].
Bayer CropScience. 2021. Roundup PowerMAX® 3 herbicide product label. https://www.cdms.net/ldat/ld0RF009.pdf. [accessed 9 Jul 2024].
Capinera JL. 2005. Relationships between insect pests and weeds: An evolutionary perspective. Weed Sci. 53(6):892–901. https://doi.org/10.1614/WS-04-049R.1.
Chowdhury I. 2024. Commercial vegetable nematode control. Georgia Pest Management Handbook. University of Georgia Extension Special Bulletin No. 28.
Coolong TW. 2017. Yellow squash and zucchini cultivar evaluation in Georgia. HortTechnology. 27(2):296–302. https://doi.org/10.21273/HORTTECH03605-16.
Cornish PS. 1992. Glyphosate residues in a sandy soil affect tomato transplants. Aust J Exp Agric. 32(3):395–399. https://doi.org/10.1071/EA9920395.
Csizinszky AA. 2005. Production in the open field, p 237–256. In: Heuvelink E (ed). Tomatoes. CABI Publishing, Oxfordshire, UK.
Culpepper AS, Grey TL, Webster TM. 2009. Vegetable response to herbicides applied to low-density polyethylene mulch prior to transplant. Weed Technol. 23(3):444–449. https://doi.org/10.1614/WT-08-135.1.
Culpepper AS, Singleton TR. 2024. Commercial Vegetable Weed Control. Georgia Pest Management Handbook. University of Georgia Extension Special Bulletin No. 28.
Devlin RM, Karczmarczyk SJ, Zbiec II, Koszanski ZK. 1986. Initial and residual activity of glyphosate and SC-0224 in a sandy soil. Crop Prot. 5(4):293–296. https://doi.org/10.1016/0261-2194(86)90066-9.
Dittmar P, Agehara S, Dufault NS (eds). 2023. 2023–2024 Vegetable production handbook of Florida. University of Florida IFAS Extension CV292.
Fennimore SA, Doohan DJ. 2008. The challenges of specialty crop weed control, future directions. Weed Technol. 22(2):364–372. https://doi.org/10.1614/WT-07-102.1.
Corporation FMC. 2017. Aim® herbicide product label. https://www.cdms.net/ldat/ld5L1010.pdf. [accessed 9 Jul 2024].
Grey TL, Vencill WK, Mantripagada N, Culpepper AS. 2007a. Residual herbicide dissipation from soil covered with low-density polyethylene mulch or left bare. Weed Sci. 55(6):638–643. https://doi.org/10.1614/WS-06-208.1.
Grey TL, Webster TM, Culpepper AS. 2007b. Autumn vegetable response to residual herbicides applied the previous spring under low-density polyethylene mulch. Weed Technol. 21(2):496–500. https://doi.org/10.1614/WT-06-121.1.
Goodman KJ, Randell TM, Hand LC, Vance JC, Culpepper AS. 2019. Cucurbit response to residual glyphosate activity from a preplant application (abstr). Proc Southern Weed Sci Soc. 72:232.
Hajihassani A. 2018. Chemical nematicides for control of plant-parasitic nematodes in Georgia vegetable crops. University of Georgia Cooperative Extension Bulletin No. 1502.
Hand LC, Vance JC, Randell TM, Shugart J, Gray T, Luo X, Culpepper AS. 2020. Effects of low-dose applications of 2,4-D and dicamba on cucumber and cantaloupe. Weed Technol. 35(3):357–362. https://doi.org/10.1017/wet.2020.129.
Illic P. 1990. Plastic tunnels for early vegetable production. University of California–Davis. Small Farm Center Publication. https://sfp.ucanr.edu/pubs/Family_Farm_Series/Veg/Production/#:~:text=These%20tunnels%20are%2018%22%20high,can%20destroy%20or%20damage%20them. [accessed 9 Jul 2024].
Johnson AM, Hoyt GD. 1999. Changes to the soil environment under conservation tillage. HortTechnology. 9(3):380–393. https://doi.org/10.21273/HORTTECH.9.3.380.
Kane SP. 2024. Ag Snapshot 2024. University of Georgia Center for Agribusiness and Economic Development. https://extension.uga.edu/publications/detail.html?number=AP129-2. [accessed 9 Jul 2024].
Kemble JM, Bertucci MB, Bilbo TR, Jennings KM, Meadows IM, Rodrigues C, Walgenbach JF, Wszelaki AL. (eds). 2024. Southeast U.S. 2024 Vegetable Crop Handbook. https://content.ces.ncsu.edu/southeastern-us-vegetable-crop-handbook. [accessed 9 Jul 2022].
Kunkel DL, Salzman FP, Arsenovic M, Baron JJ, Braverman MP, Holm RE. 2008. The role of IR-4 in the herbicide registration process for specialty food crops. Weed Technol. 22(2):373–377. https://doi.org/10.1614/WT-07-115.1.
Marini RP. 2003. Approaches to analyzing experiments with factorial arrangements of treatments plus other treatments. HortScience. 38(1):117–120. https://doi.org/10.21273/HORTSCI.38.1.117.
Monks DW, Schultheis JR. 1998. Critical weed-free period for large crabgrass in transplanted watermelon. Weed Sci. 46(5):530–532. https://doi.org/10.1017/S0043174500091049.
Moore KJ, Dixon PM. 2014. Analysis of combined experiments revisited. Agron J. 107(2):763–771. https://doi.org/10.2134/agronj13.0485.
Nichino America. 2020. ET® herbicide/defoliant product label. https://www.cdms.net/ldat/ld6CG004.pdf. [accessed 9 Jul 2024].
Olson SM, Hochmuth GJ, Hochmuth RC. 1994. Effect of transplanting on earliness and total yield of watermelon. HortTechnology. 4(2):141–143. https://doi.org/10.21273/HORTTECH.4.2.141.
Randell TM, Roberts PM, Culpepper AS. 2021. Palmer amaranth (Amaranthaceae) and at-plant insecticide impacts on tarnished plant bug (Hemiptera: Miridae) and injury to seedling cotton terminals. J Entomol Sci. 56(4):487–503. https://doi.org/10.18474/JES20-75.
Rosenberg U, Rubin B, Kafkafi U. 1988. Herbicidal activity of glyphosate in soil. Phytoparasitica. 16(4):363.
Rulevich MT, Mangan FX, Carter AK. 2003. Earliness and yield of tropical winter squash improved by transplants, plastic mulch, and row cover. HortScience. 38(2):203–206. https://doi.org/10.21273/HORTSCI.38.2.203.
Salazar LC, Appleby AP. 1982. Herbicidal activity of glyphosate in soil. Weed Sci. 30(5):463–466. https://doi.org/10.1017/S0043174500040984.
Salt Lake Holding LLC. 2024. Telone® II Soil Fumigant product label. https://www.cdms.net/ldat/ld1Q5038.pdf. [accessed 9 Jul 2024].
Schultheis JR, Cantliffe DJ, Bryan HH, Stoffella PJ. 1988. Planting methods to improve stand establishment, uniformity, and earliness to flower in bell pepper. J Amer Soc Hort Sci. 113(3):331–335. https://doi.org/10.21273/JASHS.113.3.331.
Shaner DL (ed). 2014. Glyphosate, p 240–242. In: Herbicide handbook (10th ed). Weed Science Society of America, Lawrence, KS, USA.
Sosnoskie LM, Davis AL, Culpepper AS. 2008. Response of seeded and transplanted summer squash to S-metolachlor applied at planting and postemergence. Weed Technol. 22(2):253–256. https://doi.org/10.1614/WT-07-137.1.
Sprankle P, Meggitt WF, Penner D. 1975. Adsorption, mobility, and microbial degradation of glyphosate in the soil. Weed Sci. 23(3):229–234. https://doi.org/10.1017/S0043174500052929.
Starke KD, Monks DW, Mitchem WE, MaCrae AW. 2006. Response of five summer-squash (Cucurbita pepo) cultivars to halosulfuron. Weed Technol. 20(3):617–621. https://doi.org/10.1614/WT-03-144R3.1.
Stubbs K. 2020. 2019 Georgia Farm Gate Value Report. University of Georgia Center for Agribusiness and Economic Development AR-20-01. https://caed.uga.edu/content/dam/caes-subsite/caed/publications/annual-reports-farm-gate-value-reports/2019%20Farm%20Gate%20Report.pdf. [accessed 9 Jul 2024].
Syngenta Crop Protection. 2019a. Gramoxone® SC 2.0 herbicide product label. https://www.cdms.net/ldat/ldAGR031.pdf. [accessed 9 Jul 2024].
Syngenta Crop Protection. 2019b. Reflex® herbicide product label. https://www.cdms.net/ldat/ld6BJ037.pdf. [accessed 9 Jul 2024].
Trader BW, Wilson HP, Hines TE. 2008. Control of yellow nutsedge (Cyperus esculentus) and smooth pigweed (Amaranthus hybridus) in summer squash with halosulfuron. Weed Technol. 22(4):660–665. https://doi.org/10.1614/WT-08-016.1.
US Department of Agriculture. 2016. United States Standards for Grades of Summer Squash. Specialty Crops Inspection Division Publication No. 81 FR 51297. https://www.ams.usda.gov/sites/default/files/media/SummerSquashStandard.pdf. [accessed 9 Jul 2024].
US Department of Agriculture. 2023. Georgia Agricultural Facts. https://www.nass.usda.gov/Statistics_by_State/Georgia/Publications/More_Features/GAAgFacts2023.pdf. [accessed 9 Jul 2024].
University of Georgia, Center for Agribusiness and Economic Development. 2020. Farm Gate Value Survey and Reporting System-Yellow Squash Detailed Report. https://farmgate.caes.uga.edu/Reporting_DetailedReports.aspx. [accessed 9 Jul 2024].
University of Georgia, Center for Agribusiness and Economic Development. 2022a. 2020 Georgia Farm Gate Value Report. https://caed.uga.edu/content/dam/caes-subsite/caed/publications/annual-reports-farm-gate-value-reports/Farm%20Gate%20Report%202020.pdf. [accessed 9 Jul 2024].
University of Georgia, Center for Agribusiness and Economic Development. 2022b. 2021 Georgia Farm Gate Value Report. https://caed.uga.edu/content/dam/caes-subsite/caed/publications/annual-reports-farm-gate-value-reports/2021_GeorgiaFGVReportDec2022%20(1).pdf. [accessed 9 Jul 2024].
University of Georgia, Center for Agribusiness and Economic Development. 2024. 2022 Georgia Farm Gate Value Report. https://caed.uga.edu/content/dam/caes-subsite/caed/publications/annual-reports-farm-gate-value-reports/2022%20Farm%20Gate%20Value%20Report.pdf. [accessed 9 Jul 2024].
VanWychen L. 2022. Survey of the most common and troublesome weeds in broadleaf crops, fruits, & vegetables in the United States and Canada. Weed Science Society of America National Weed Survey Dataset. https://wssa.net/wp-content/uploads/2022-Weed-Survey-Broadleaf-crops.xlsx. [accessed 9 Jul 2024].
Wallace RD, Culpepper AS, MacRae AW, Sosnoskie LM, Grey TL. 2012. Vegetable crop response to EPTC applied preemergence under low-density polyethylene and high barrier plastic mulch. Weed Technol. 26(1):54–60. https://doi.org/10.1614/WT-D-11-00016.1.
Walters SA, Nolte SA, Young BG. 2005. Influence of winter rye and preemergence herbicides on weed control in no-tillage zucchini squash production. HortTechnology. 15(2):238–243. https://doi.org/10.21273/HORTTECH.15.2.0238.
William RD, Warren GF. 1975. Competition between purple nutsedge and vegetables. Weed Sci. 23(4):317–323. https://doi.org/10.1017/S0043174500053108.
Wolfe K, Stubbs K. 2018. 2017 Georgia Farm Gate Value Report. University of Georgia Center for Agribusiness and Economic Development AR-18-01. https://caed.uga.edu/content/dam/caes-subsite/caed/publications/annual-reports-farm-gate-value-reports/2017-farm-gate-value-report.pdf. [accessed 9 Jul 2024].
Wolfe K, Stubbs K. 2019. 2018 Georgia Farm Gate Value Report. University of Georgia Center for Agribusiness and Economic Development AR-19-01. https://caed.uga.edu/content/dam/caes-subsite/caed/publications/annual-reports-farm-gate-value-reports/2018%20Farm%20Gate.pdf. [accessed 9 Jul 2024].
Wright-Smith HE, Culpepper AS, Randell-Singleton T, Vance JC. 2023. Transplant broccoli and collard response to the residual activity of glyphosate applied preplant. Weed Technol. 37(1):71–75. https://doi.org/10.1017/wet.2023.9.
Zimdahl RL. 2018. Fundamentals of Weed Science (5th ed). Academic Press, San Diego, CA, USA.