ASHS 2025 Conference

Weed overgrowth in high-value crops like onions remains a major challenge due to labor costs, herbicide resistance, and environmental concerns. Robotic laser-based weed control offers a precise, chemical-free alternative capable of targeting individual weeds while protecting crop health and the environment. This research introduces the application of a Clavel-based delta parallel robot for precision weed elimination using a high-power diode blue light laser. The delta robot employed in this study features three degrees of freedom and is capable of achieving maximum accelerations up to 20 m/s². It consists of aluminum proximal arms connected to servo motors and carbon fiber distal arms, reducing weight and enhancing agility. These servo motors are housed within a top base constructed from ABS 3D printed parts. Movement calculations and inverse kinematics are managed by an embedded ARM Cortex-M3 controller integrated with the servo motors. A 450 nm, 10W diode laser serves as the robot's end-effector, actuated using the Transistor-transistor logic (TTL) signals. Both robot movements and laser activation are simultaneously controlled through an external Arduino Mega 2560 microcontroller, leveraging a custom-developed C library to ensure workspace safety and precision. Experiments conducted to assess positional accuracy involved 100 trials, resulting in a mean radial positional error of 0.83 mm. Further experiments measured laser exposure time and stand-off distance. The results showed complete weed destruction in less than 6 seconds at distances of up to 100 mm. These results support the robot's effectiveness in targeted weed management for precision agriculture.

The use of pre-emergence herbicides under plastic mulch is an effective strategy for weed control in plasticulture beds in vegetable production systems. S-metolachlor is a pre-emergence herbicide labeled for application in soil prior to laying plastic mulch in tomato production in Florida. However, the risk of crop injury has limited its adoption in plasticulture systems, highlighting the need for crop-safe herbicide application approaches. This study aimed to evaluate the potential of herbicide safeners including chemical seed treatments and activated charcoal in mitigating tomato transplant injury from herbicides such as S-metolachlor. A greenhouse experiment was conducted at the Southwest Florida Research and Education Center (SWFREC) in Immokalee, FL, across two trials: March–June (Trial I) and August–November (Trial II) of 2024. Field soil was collected and used in pots for both trials. Treatments included tomato seed pre-treatments with benoxacor or fenclorim, and transplant root treatments with activated charcoal applied either as a root dip or poured into planting holes. All treated transplants and non-treated controls were grown in S-metolachlor-treated soil. Seed pre-treatment with benoxacor or fenclorim reduced crop injury by over 63% compared to non-treated controls. Activated charcoal applied to transplant roots reduced injury by 40–70% in Trial I and by over 70% in Trial II. Chlorophyll content was consistently higher in safener-treated plants, with activated charcoal increasing levels by more than 16% at 2 weeks after transplanting (WAT) and by 11–20% at 6-WAT. Similarly, benoxacor and fenclorim treatments improved chlorophyll content by 12–19% at 6-WAT. Root biomass in non-treated transplants was reduced by 56–70% due to S-metolachlor exposure. In contrast, both activated charcoal and seed-applied safeners helped preserve root biomass, with benoxacor and fenclorim reducing root weight loss by 65–70% compared to untreated controls. Overall, the results demonstrate that both seed-applied (benoxacor, fenclorim) and root-applied (activated charcoal) safeners are effective in mitigating S-metolachlor injury in tomato transplants and may offer viable strategies for enhancing crop safety in plasticulture-based vegetable production.

A successful Christmas tree production requires a good and effective weed management program. Most common weed control practices in Christmas tree production involve mechanical mowing and the application of chemical herbicides. Repeated applications of the existing herbicide options have resulted in the development of herbicide-resistant weed species. It is also important to test newer herbicides to expand the list of herbicide options. Hence the objectives of this research were to evaluate labeled (1X) and double (2X) rates of newer herbicides for weed control efficacy and for phytotoxicity in Fraser fir variety of Christmas tree. Field experiments were conducted in summer and fall 2024 at a commercial Christmas tree farm located at Gobles, MI. Christmas tree variety chosen for the experiment was four-year-old Fraser fir (Abies fraseri). The herbicide treatments included glyphosate trifloxysulfuron-sodium, glyphosate flumetsulam, glyphosate flumetsulam clopyralid, glyphosate chlorimuron, glyphosate cloransulam, glyphosate topramezone, glyphosate flumioxazin. Out of these treatments, the last two were considered as industry commercial standards. The control treatment included only glyphosate. All herbicides were tested for their labeled (1X) rates and double (2X) rates. Treatments were applied before bud break as directed application towards the lower 18 inches of the trees with a carbon dioxide backpack sprayer calibrated at 27 gallons per acre output. The experiments were complete randomized block design with four replications of each treatment. Data were collected at 1, 2, 3, and 4 months after treatment (MAT) which included visual estimation of weed control based on a scale of 0% to 100% (0% meaning no weed control and 100% meaning complete weed control) and phytotoxicity based on a scale of 0% to 100% (0% meaning no plant injury and 100% meaning complete death of a branch). Dominant weed species were recorded as well. Data were analyzed by ANOVA in SAS 9.4 and means were separated out by Tukey’s HSD test. Results showed that 1X rates of glyphosate chlorimuron and glyphosate trifloxysulfuron-sodium provided 70%-90% weed control till 4 MAT and their 2X rates showed no significant injuries to the Fraser fir variety till 4 months. Hence, glyphosate chlorimuron and glyphosate trifloxysulfuron-sodium can be additional options for Christmas tree growers for weed control in future. However, long-term multiple year studies are still required based on different herbicidal rates and on different varieties of Christmas trees for expansion of these herbicide labels.

Specialty and organic crop weed management strategies are challenging due to limited chemical control products with good efficacy that are cost effective. The need for new bioherbicide modes of action has become increasingly urgent in modern agriculture as most bioherbicides have nonspecific modes of action with no systemic activity. Introducing new bioherbicides that are also registered as organic is essential to diversify weed control strategies. By fostering innovations in bioherbicide development agricultural systems can be more environmentally friendly by preserving ecosystems while maintaining the ability to feed a growing global population. Manuka oil is derived from the leaves and branches of the Manuka tree (Leptospermum scoparium) and contains β-triketones. The β-triketone rich fraction contains leptospermone that inhibits a key enzyme, p-hydroxyphenylpyruvate dioxygenase (HPPD). This process directly inhibits carotenoid biosynthesis, upstream in the biochemical pathway, which causes damage to the photosynthetic apparatus and leads to bleaching of the leaf tissue which eventually kills the plant. There were three studies that examined the efficacy of β-triketone extract against Lolium multiflorum, Amaranthus retroflexus, and Abutilon theophrasti. The studies were 1) pre-emergence β-triketone extract ranging from 0 to 2.5 mg ml-1, 2) post-emergence β-triketone extract ranging from 0 to 6%, and 3) post-emergence β-triketone extract at 0.5 and 2.0% with five different organic adjuvants. In the pre-emergence study, there were significant differences between the β-triketone extract treatments and 100% weed control down to 0.625 mg ml-1. In the post-emergence study, there was significant decreases in weed height and fresh and dry mass when compared to the control treatment. However, the adjuvants did not have any effect on weed height and fresh and dry mass. Thus, there is significant evidence that commercializing a water soluble β-triketones enriched extract of Manuka oil can be an effective weed control, especially as a pre-emergent bioherbicide for specialty and organic crop production.

A forum for discussion of potential collaborations with regards to plant growth and culture – i.e. propagation, root growth, water management, weed control, PGRs, plant nutrition, etc.

Many types of mulch have been shown to reduce weed growth in container crops. In the past, mulch use in nurseries was not as feasible due to its high cost, but as costs of hand weeding increase, labor shortages become more severe, and environmental awareness rises, utilization of mulch has become more popular in recent years. Parboiled rice hulls are a waste product of the rice industry and are dry rice husks removed from rice grains. They are light weight, hydrophobic and make for an ideal mulch choice in container nursery production and have been previously evaluated for use as a weed management tool in container nurseries. However, research was typically conducted on a limited number of species and studies were performed in greenhouses or other protected structures. The objective of this research was to evaluate rice hulls for control of five common nursery species in an outdoor environment in Florida during the summer season. Nursery pots (1.7 L) were filled with a standard pinebark based potting soil and amended with standard control release fertilizers via incorporation. Upon filling, pots received one of three levels of rice hulls, 0 cm or the non-treated control, 1.3 cm, or 2.5 cm. To test efficacy, approximately 30 seeds of crabgrass (Digitaria sanguinalis), doveweed (Murdannia nudiflora), longstalk Phyllanthus (Phyllanthus tenellus), spotted spurge (Euphorbia maculata), or eclipta (Eclipta prostrata) were sown either above or below the rice hull mulch layers mentioned above. Data collected included weed coverage ratings (0 to 100%) at 4, 6, 8, 10, and 12 weeks after planting (WAP) and shoot dry weights at 12 WAP. Few differences were observed among the different depths of mulch when seeds were placed below. For seeds placed on top of the mulch, the higher 2.5 cm depth generally provided greater control. For all 5 weed species, control significantly increased when seeds were placed on top of the mulch compared to seeds beneath the mulch layer. Control, as measured by a percent reduction in shoot weight compared to the non-mulched control, ranged from 80 to 100% for seeds placed on top compared with decreases of 0 to 40% when seeds were placed below mulch. Overall, data suggest that because rice hulls are more effective on weed seeds placed on top of the mulch layer, growers would likely see increased efficacy when mulching as soon as possible after potting.

Elevated temperatures can intensify weed issues by accelerating weed growth and germination, especially for C4 species, due to their heat tolerance and efficient carbon fixations, making their control more challenging. Temperature also influences herbicide absorption, translocation, and metabolism. Large crabgrass (Digitaria sanguinalis), a highly problematic C4 weed, poses a significant threat to nursery and field-grown ornamentals under these conditions. This study aims to evaluate the efficacy of postemergence herbicides at different rates (0.5X, 1X, 2X) under normal and elevated temperatures for managing large crabgrass in ornamental production. Experiments were conducted in summer and fall 2024 using a growth chamber and an open hoop house setup. Large crabgrass seeds were sown in pots filled with standard substrate, irrigated, and placed in separate growth chambers where temperatures were maintained at normal (22–28°C) and at 2-5°C above the species’ optimum range (28-34°C). Once weeds reached the 3–6 leaf stage, they were transferred to an open hoop house for herbicide application. Postemergence herbicides such as topramezone and glyphosate were applied at 0.5X, 1X, and 2X rates using a CO₂ backpack sprayer. After the restricted entry interval, treated weeds were placed back to their respective growth chambers and maintained there for four weeks. A control treatment without herbicide application was maintained in both growth chambers. Weed control ratings were visually assessed at 1, 2, 3, and 4 weeks after treatment (WAT) using a 0–10 scale, where 0 = no control (green foliage, upright growth, no damage) and 10 = complete plant death (dark brown foliage, no green tissue, collapsed structure)). At 4 WAT, all weeds were harvested, and dry weight of aboveground parts of weed was recorded. The experiment followed a completely randomized design with eight replications per treatment and was repeated twice. Data were analyzed using ANOVA in SAS 9.4, and treatment means were separated using Fisher’s LSD test. The results showed that at 4 WAT glyphosate weed control efficacy at normal temperature was 88% which reduced to 73% under elevated temperature condition. Whereas the high temperature increased topramezone efficacy by 10%. The lowest amount of weed dry weight was observed at 2X rates in high temperature conditions, but no difference was observed among rates at normal temperature. Hence it can be concluded that with an increase in temperature, higher rates of the tested herbicides will be required for effective weed management in ornamentals.

Intensive cultivation in high tunnel production systems is leading to the emergence of soilborne pest and pathogen issues which over time can compromise crop productivity and profitability. Growers facing such challenges are in search of sustainable and effective solutions capable of suppressing soilborne pests and pathogens while preserving soil health. Anaerobic soil disinfestation (ASD) is a broad-spectrum pre-planting biological approach proposed for the management of soilborne issues affecting high-value specialty crops. ASD is applied by incorporating in the soil readily labile organic amendments as a carbon (C) source, tarping the soil with an impermeable film, and irrigating the soil to saturation. Although ASD already proved to be effective against a range of soilborne pests and pathogens across different US regions, crops, and production systems, its adoption at commercial scale remains relatively limited. Factors hindering the adoption of ASD include application cost, complexity of microbial driven processes, and lack of knowledge of the method, its implementation steps, and its efficacy and benefits. Capitalizing on over six years of research aimed at optimizing the ASD application method and its integration in high tunnel production systems in Pennsylvania, a series of on-farm ASD applications were conducted over the 2023 and 2024 growing season with the purpose of demonstrating the technology and let growers evaluate first-hand its viability and efficacy. The on-farm trials were conducted on selected farms growing vegetables and small-berries in high tunnels and employing both conventional and organic production methods. Raised-bed and broadcast application were tested along with the use of clear and black film. Wheat middlings alone or in combination with feed-grade sugarcane molasses were tested as C sources testing different soil incorporation equipment and methods. Depending on the specific crop system, and the grower planting schedule, ASD was applied between the end of the Spring (before a late high tunnel crop planting) and mid-October (after an early high tunnel crop). Parameters measured included soil redox potential, temperature, pH, electrical conductivity and mineral nitrogen. The level of anaerobiosis achieved varied depending on the amount of labile carbon applied, the type of tarp used, and the temperature levels achieved. High levels of cumulative soil redox potential were achieved and the use of clear film allowed to achieve relatively higher soil temperatures and cumulative redox potential levels in most on-farm applications. Additional demonstration efforts are needed to facilitate the adoption of ASD and demonstrate its efficacy.

Organic farming with its reliance on natural fertilizers, cover cropping, and crop rotation, presents a sustainable approach to food production. However, a significant challenge in organic production is insect and disease management. Organic insecticides often have limited efficacy, are expensive, and require repeated applications. Mesotunnels, medium-sized (36-40 inches tall) tunnels covered with insect netting, have emerged as a pest management tool for organic vegetable growers. This study evaluated the effectiveness of mesotunnel and low tunnel systems for pest management and season extension in organic Chinese cabbage (cultivar ‘Minuet’) production. The first season of this two-year study was conducted in Fall 2024 on certified organic land at Iowa State University Horticulture Research Station, Ames, IA. The experiment was set up as a randomized complete block design with four replications and following treatments: i) 85 g ExcludeNet insect netting, ii) 0.55 oz Agribon row cover, iii) 85 g ExcludeNet insect netting + OMRI-listed insecticide iv) OMRI-listed insecticide, and v) an untreated control, uncovered with no insecticide. Weekly pest surveillance focused on Brassica insect pests such as aphids, loopers, harlequin bugs, flea beetles, and their damage was recorded. Hobo data loggers recorded variations in light intensity, air and soil temperature, and relative humidity to observe microclimate variations in each treatment. At harvest, yield data was categorized as marketable or nonmarketable and graded according to USDA commercial standards. Among all treatments, the highest marketable produce was recorded in ExcludeNet + OMRI-listed insecticide treatment (42%), followed by Agribon row cover (31%) and the lowest in OMRI-listed insecticide (15%) during the first harvest. The earlier maturity in these treatments was likely due to warmer temperatures and improved humidity regulation under the tunnels. The insect abundance and their damage on leaves was significantly lower in ExcludeNet & ExcludeNet + OMRI-listed insecticide treatment. Integrating netting and row covers with limited use of organic insecticides provided the highest pest suppression, suggesting that physical barriers can effectively optimize pest management and enhance marketability in organic vegetable production systems. Findings from this study will inform growers and the research community about the feasibility of insect nettings as a sustainable pest management tool in organic specialty crop systems.

Sunn hemp (SH, Crotalaria juncea L.) is used in Florida strawberry production as an off-season summer legume cover crop to provide agroecosystem services such as weed and plant-parasitic nematode (PPN) suppression. Bicultures of SH with sorghum-sudangrass (SS) (Sorghum bicolor Moench × S. sudanense [Piper] Stapf) are of interest to reduce the cost of SH use. Our study objective was to determine whether bicultures retain the weed and PPN suppression benefits provided by SH grown in monoculture. A replacement series experiment was conducted in summer 2022 and repeated in 2023 in north-central Florida in a PPN-infested field. A factorial treatment arrangement of five SH:SS biculture proportions (100:0, 75:25, 50:50, 25:75, and 0:100) and three seeding rates (20, 40, and 60 lb/acre) were evaluated in a randomized complete block design with four replications. A no-cover crop, weedy control was also included in each block. Data were collected on cover crop biomass and carbon: nitrogen ratio (C:N), weed density, weed biomass, and PPN populations at eight weeks after planting. Bicultures consistently produced higher total cover crop biomass than the SH monoculture. Bicultures were as effective as the SH monoculture in reducing total weed density and resulted in either lower or equivalent total weed biomass. Averaged over year, only the 60 lb/acre seeding rate had a lower total weed density than the 20 lb/acre rate. In 2022, both the 40 and 60 lb/acre seeding rates resulted in lower weed biomass than the 20 lb/acre rate, while seeding rate had no significant effect on total weed biomass in 2023. Root-knot nematode populations in both years and sting nematode populations in 2022 were detected at levels too low for analysis. However, in 2023, the lowest and highest sting nematode populations occurred with the SH and SS monocultures, respectively; and sting nematode populations increased as the proportion of SS in the bicultures increased. Bicultures with ≤50% SS had significantly higher sting nematode populations than the weedy control. An increase in C:N was observed as SS proportion in bicultures increased. Thus, we conclude that SH/SS bicultures maintain the weed biomass suppression benefits of SH monocultures while increasing cover crop biomass. However, bicultures may lead to higher sting nematode populations, which will be of concern in organic strawberry production where soil fumigation is not permitted. Growers will also need to consider the effects of the higher C:N ratio of biculture residue on nitrogen fertilizer immobilization.

Minnesota (MN) in the US ranks 2nd for corn silage production and 3rd for soybean production. Studies have shown that off-target movement (drift) from an unshielded sprayer, in row crops, can range from 1 to 16% of the target dose; however, boom height and wind can double or triple these doses. Pre-study 37 pesticide residue tests were conducted in five Minnesota nurseries in 2018. Nine different herbicides were detected in the 37 tests. Glyphosate (sold as Roundup Power Max 32% glyphosate) became the focus of 2019 studies, conducted at concentrations of 0, 6, 18 and 54% for glyphosate as drift events. Relating ppm’s disclosed in laboratory analyte foliar residue samples collected by various state agriculture departments after drift events to injury symptom, development, and growth reduction or time after application have ever been conducted for nursery crops. From personal communication with nursery owners experiencing neighbor’s drift event (MD; KY, OH, MI, FL) the average time from the drift event to recognizing problems, and sample collection is six weeks (6 weeks after drift event) (6 WADE). Slower metabolism of glyphosate at higher residues, explained our finding that the largest residues were detected in all, but one species/ treatments used with glyphosate, versus three other herbicides examined or in combinations. Higher residues meaning higher injury, does not occur with glyphosate. Potentially high residues mean slow metabolism for glyphosate, and thus less injury. In five cases glyphosate applied alone had no impact on growth measured as caliper over the season, even though glyphosate had the highest residue in three of the five. In only one case was caliper growth reduction highest with glyphosate (Syringa 18%) over the entire study. In terms of phytotoxicity rating, glyphosate caused no commercially unacceptable injury in four cases. Residues increased with all rates on the three species evaluated between 3 DADE and 6 WADE. With Acer freemanii and Tilia cordata residue levels declined slightly between 6 WADE to 14 WADE with all rates. Only, Syringa reticulata showed an increase in foliar residues between 6 WADE to 14 WADE. Since carry over injury the next year (or three) is a concern with all glyphosate applications to perennial plants, all trees were observed in 2020. None were commercially acceptable and in severe decline (regardless of rate) in spring 2020, only 6% glyphosate on Syringa survived to the fall , and by spring 2021 were dead.

The ornamental crop industry in the United States, is a billion-dollar industry. Weed management in nursery container production is a significant challenge, as weeds compete with ornamentals for essential resources, reducing plant quality, marketability, and overall profitability. Controlling weeds in containers is one of the highest production costs encountered by nursery growers, often exceeding $4,000 per acre. Previous research results have shown that weeds within a restricted area can reduce ornamental growth by 60%. Some of the most problematic weed species identified in the container production includes liverwort, hairy bittercress, oxalis, chick weed, etc. Liverwort is one of the major weed problems in greenhouses and nursery container production. Historically liverwort has been reported as a weed issue in cooler regions of the Northeast and Pacific Northwest regions of the United States. It thrives well in moist, low UV light condition, and in presence of high fertility and a cool temperature. Hence, nurseries and greenhouses are ideal places for their growth. Growers rely mostly on hand weeding to manage these problematic weeds, especially inside the greenhouse production system as there are limitations in applying herbicides within greenhouse conditions. Since hand weeding is very time consuming, laborious, and expensive, there is an immediate need for research to improve chemical weed control practices through alternative pesticides that can be applied to container production and improve growers’ productivity and profitability. New plants are always being added to nursery production so phytotoxicity studies are also required. Some previous research has focused on evaluating synthetic versus organic herbicides for weed control inside greenhouse conditions. However, there is almost no information available on how alternative pesticides such as fungicide or miticides can be used for weed control in container production and whether they will be safe on ornamentals. This significant knowledge gap has led to the development of this master’s research proposal. Hence the objectives of this research proposal are: To evaluate the preemergence efficacies of fungicide and miticide as alternative pesticides on liverwort control; To assess newer herbicide formulations and rates for controlling weeds and phytotoxicity on container-grown woody shrubs; To disseminate the research results to the growers and scientific community. Preliminary results have shown that miticide Tetracurb Max and fungicide Zerotol can provide suppression of liverwort in containers without causing any significant injuries to the woody ornamental shrubs.

The changing climate is impacting weed ecology and growth patterns in agricultural production systems. General understandings of temperature and moisture requirements have been documented for different weed species, however, there is evidence that production practices and environmental factors affect weed species response to temperature and moisture. Laboratory studies were initiated in 2023 at the University of Idaho Research and Extension Center to determine the germination temperature and moisture requirements of Italian ryegrass (Lolium multiflorum) and spring wheat (Triticum aestivum) collected in Idaho and Washington. For the germination temperature requirement experiments, weed populations and wheat cultivars were grown on a thermogradient table with 10 varying temperatures between 4 C and 35 C. In the germination moisture requirement experiments, polyethylene glycol (PEG 8000) obtain 10 different osmotic potentials (0 to -2 MPa) at temperatures >12 C, there were no differences in germination speed and maximum germination between the Italian ryegrass and spring wheat. However, Italian ryegrass had faster germination speed and greater maximum germination at temperatures

Recently, Impatiens necrotic spot virus (INSV), transmitted by the western flower thrips (Frankliniella occidentalis), has emerged as a major limiting-factor in lettuce production, causing up to 100% yield losses in California. Florida, the third-largest lettuce-producing state in the US, following California and Arizona, cultivates approximately 11,000 acres of lettuce annually. While cases of INSV have not been reported in Florida lettuce, F. occidentalis is a common pest in many crops in Florida including lettuce, the virus poses a significant threat to lettuce crops if introduced. Since INSV is exclusively transmitted by thrips, effective thrips management is crucial to mitigate its impact. Currently, management of F. occidentalis mainly relies on pesticides, however, over-reliance on pesticides may lead to insecticide resistance and further raising environmental and health risks. An integrated pest management approach, incorporating thrips-resistant lettuce cultivars as a first line of defense, could provide a sustainable solution to mitigate the possible negative effects of INSV. The aim of this study was to identify lettuce germplasm with resistance to F. occidentalis. In no-choice experiments, 39 lettuce germplasms including commercial cultivars were evaluated for the resistance to F. occidentalis. These germplasms were planted under thrips-free conditions and plants were placed individually to thrips-proof container and infested with 7 female thrips when they developed 5-6 true leaves. The thrips colony was reared on Okeechobee cultivar, a cultivar susceptible to other sap-feeding insects, which was also used as control for the experiments. Fourteen days post-infestation, the number of larvae and adult thrips per plant. Experiments were conducted in an insectary room maintained at 25 ± 1 °C with a photoperiod of 16-hour light and 8-hour dark. Five replicates (plants) were conducted for each lettuce germplasm. Several germplasms, including breeding lines 50100, 70096, and 70882, cultivars such as Bambino, La Brillante, Manatee, Emperor, Hacienda, and Valmaine, as well as plant introductions (PI) 204707 and 251246, exhibited significantly less larvae (Alpha level 0.05) than Okeechobee, suggesting resistance to F. occidentalis. On the other hand, breeding line 60183 and Gator had significantly higher number of larvae thrips than Okeechobee suggesting high susceptibility to F. occidentalis. These findings highlight promising candidates for further identification of genomic regions responsible for resistance against F. occidentalis and to develop resistant lettuce cultivars that could be a first-line of defense against INSV. Since INSV has not been reported in Florida, this underscores the importance of proactive resistance breeding efforts to prevent potential outbreaks.

Air-blast sprayers with intelligent spray technology can apply pesticides more efficiently to tree canopies than conventional sprayers. However, little research has examined their effectiveness for trunk applications to control pests such as flatheaded borer (FHB). FHB larvae chew directly into the trunk upon hatching, necessitating thorough coverage with contact insecticides. Our objective was to explore the potential of using intelligent variable-rate spray technology to achieve thorough coverage on tree trunks. A red maple (Acer rubrum) block was divided into three plot-row-types: single-row (SR), double-row (DR; South and North rows), and triple-row (TR; South, interior, and North rows). Water sensitive paper (WSP) wraps were used to assess spray coverage. Wraps were secured around trunks of ten trees per row at 15 and 40 cm above the ground. Plots were sprayed with water using a Jacto A400/850 air-blast sprayer in constant-rate (CR) and variable-rate (VR) modes using the Smart Apply intelligent spray control system. CR discharged 69% higher spray volume than the VR mode (P < 0.0001). SR had >99% coverage; coverage in SR was not affected by spray mode or wrap height (P ≥ 0.0592). For DR, coverage ranged from 98.4% to 99.9%, and spray mode did not affect coverage on upper wraps (P ≥ 0.0829) within a row, while CR (99.6%) had lower coverage than VR (99.9%; P = 0.0043) for lower wraps in the northern row. However, TR coverage varied with the spray mode and wrap height (P < 0.0001). Upper wraps in the southern and interior rows had higher coverage from CR than VR, 98.6% versus 89.9% (P = 0.0019) and 98.7% versus 78.8% (P = 0.0137), respectively. For lower wraps, both the southern and interior rows had higher coverage from CR than VR, 98.5% versus 93.4% (P = 0.0019) and 99.5% versus 94.0% (P = 0.0137), respectively. Coverage was very high, i.e., ≥98.0% for 18 of 24 treatment combinations and ≥89.9% for 23 of 24 treatment combinations, but did not achieve 100%. There was no advantage to CR for SR or DR. For all plot-row-types and spray modes, the spray rate was higher than desired. CR sprayed 480, 251, and 210 GPA in the SR, DR, and TR plots, respectively, while VR discharged 239, 156, and 140 GPA. Future research should examine the use of adjuvants to increase coverage and determine a coverage range that balances acceptable FHB control, labor costs, and spray volume.

The current study seeks to improve our ability to utilize RNA interference in developing novel tactics for management of arthropod pests related to crop protection and vector mitigation. The use of this technology in the development of novel arthropod control strategies has been substantially limited relative to its potential for implementation, and inherent advantages over traditional means for controlling pests. Past efforts in applying RNA interference as a strategy for management of arthropod pests have been limited by substantial hurdles that this research seeks to address. While the potential for the utility of RNAi in pest management has been recognized in the past several decades, previous research has found that the practicability of the technology in an applied setting is stifled by a number of factors, including the molecular instability of RNA, host susceptibility, evolved resistance, efficacy, and off-target effects. Our interest in exploring the potential for RNAi as a strategy for pest management application comes from recent developments in our investigation into the genomic basis of toxin resistance in insects. This work suggests the vital importance of a family of genes found in all insects that we believe may function as a target for RNAi that would alleviate many of these stated concerns; these genes are directly involved in insect immunity, they are highly conserved throughout insects yet have enough sequence variability to allow for species-specific targeting, and many of these genes cause lethality when silenced using RNA interference. In our analysis, we highlight the potential of this family of genes in being leveraged towards pest management applications across arthropod species; and in our experimental study we target a member of this gene family in 2 species of fruit flies, Drosophila melanogaster and D. sechelia, as well as a target gene that has previously been shown to cause lethality when knocked down in fruit flies. We show that member genes in this family may be an effective target for the development of RNAi based bioinsecticidal approaches, with potential applications in a broad range of arthropod pests.

Viruses are a major biotic threat to cucurbit production in the southeastern United States. Many important cucurbit viruses are transmitted by whiteflies and aphids. Recent cucurbit virus research in Georgia is predominantly focused on whitefly-transmitted viruses (WTVs) and research is lacking on the aphid-transmitted viruses (ATVs) in cucurbit crops of Georgia. This study investigates the occurrence, prevalence, and emergence of ATVs in pumpkin and winter squash crops grown in a vegetable research farm at the University of Georgia-Tifton Campus during the fall season of 2022 and 2023. We screened plants for characteristic virus symptoms such as mosaic, mottling, yellowing, chlorotic spots, vein clearing, shoestring, upward curling, crumpling, blistering, and deformation of leaves. We collected symptomatic leaf samples of pumpkin and winter squash from the field. We processed the leaf samples for small RNA libraries for high-throughput sequencing (HTS) to identify ATVs present in the samples. We amplified viral genes for sanger sequencing and ran quantitative polymerase chain reactions (qPCR) for molecular validation of HTS results. HTS analysis revealed the presence of two ATVs, zucchini yellow mosaic virus (ZYMV) and papaya ringspot virus (PRSV). The qPCR results suggested a significant temporal shift in ATV’s abundance in these two crops. In 2022, PRSV and ZYMV incidence was observed in 56.25% and 31.25% pumpkin leaf samples. In winter squash, PRSV and ZYMV incidence was found in 50% and 32.14% leaf samples. Mixed infection of both viruses was at 28.12% for pumpkin and 25% for winter squash. In 2023, PRSV was not detected in pumpkins, and it was detected at a negligible level (0.62%) in winter squash. ZYMV was predominant in pumpkin (61.25%) and winter squash (42.50%). Phylogenetic analysis of ZYMV-encoded coat protein (CP) and helper component-protease (HC-Pro) suggested a close relationship with the European isolates. However, PRSV-encoded CP and NIa-VPg showed a close relationship with isolates from Australia, Papua New Guinea, Spain, and the United States. To the best of our knowledge, this is the first study to suggest single or mixed infections of ZYMV- and PRSV-infected pumpkin and winter squash in Georgia, USA. The findings of this study will serve as an important foundation for future research to understand the complex interactions between insect-transmitted viruses in cucurbit crops, which is vital for developing resistant cultivars and effective virus management strategies for commercial cucurbit vegetable crop production.

The Christmas tree industry is a million-dollar industry in the United States. Like all crop production systems, Christmas trees are also affected by weeds. Noxious plants such as Canada thistle, horsenettle, poison ivy, and pokeweed compete with Christmas trees not only for light, space, moisture, and nutrients but also harbors pests and pathogens. Additionally, they attract wild animals like deer which are detrimental to this tree production. Large weed species create significant difficulty in crop management practices and intercultural operations. Christmas trees are more prone to damage from weeds in the seedling beds and the first three years in the field after transplantation. Young trees often suffer moisture stress due to weeds and succumb to drought. Once established, weeds are very difficult to manage, particularly the management of vining and woody weeds without damaging the Christmas trees is almost impossible. In severe cases, they devastate the whole production system and cause unbearable losses to growers. The most commonly used method for weed management in Christmas tree production is the application of chemical herbicides. Herbicides can cause severe injury to Christmas trees if applied inappropriately and can cause environmental issues. In addition, repeated use of the same herbicides can trigger herbicide resistance in weed species. Chemical mowing is a weed control technique that has been implemented in Florida citrus production, and it has been successful. Chemical mowing consists of the use of sublethal rates of postemergence herbicides in conjunction with mechanical mowing. However, there is no data or research showing whether this can be implemented in the flat land Christmas tree production system. How can chemical mowing help prevent weed shifts and herbicide resistance from developing? These significant knowledge gaps have led to the development of this master’s research proposal. Hence the objectives of this research proposal are: Developing a chemical mowing strategy in Christmas tree production by evaluating the efficacies of three different postemergence herbicides at lower rates combined with mechanical mowing; Evaluating their phytotoxic effects on two different varieties of Christmas trees; Determining the optimal moisture range for efficient chemical mowing. The preliminary results showed that an effective weed control can be achieved in Christmas tree production at sublethal rates of postemergence herbicides. Also, no significant injury was observed in Christmas trees due to chemical mowing.

Weeds are a continual, year-round threat to nursery profitability due to their negative impact on crop growth, quality, and marketability, as well as the increased need for pesticide use and manual labor. In recent years, many nurseries have adopted parboiled rice hulls mulch as an alternative to herbicides. Rice hulls are lightweight, easy to apply, transport, and hydrophobic, making them an effective mulch for container-grown ornamentals. Previous research has demonstrated that rice hulls can provide excellent weed suppression when applied at sufficient depths. However, mulch is often applied 2–3 weeks after potting, during which time weed seedlings may emerge. There is a lack of research on the survivability of small weed seedlings that emerge prior to mulch application, and whether mulching at this stage could serve as a viable alternative to manual weeding. Therefore, this study aimed to evaluate the effect of rice hull mulch depth on the emergence of eclipta (Eclipta prostrata) and phyllanthus (Phyllanthus tenellus) at two growth stages. Square 1.7 L nursery containers were filled with a substrate composed of pine bark, peat, and sand (80:10:10 v: v: v), amended with dolomitic lime (target pH 5.5) and a controlled-release fertilizer [Osmocote® Plus 21-4-8, (8–9 month)]. Containers were seeded with either eclipta or phyllanthus which were allowed to grow, reaching one of two developmental stages including the cotyledon to 1-leaf or 2–4 leaf stage, using staggered sowing dates. Seedlings were then thinned to five weed plants per container, and mulch was applied at depths of 0, 0.6, 1.3, 2.5, and 5 cm. Weed emergence was recorded at 2, 4, 8, 12, and 16 weeks after mulching, and shoot dry weight was measured at trial conclusion. All containers were maintained in a greenhouse and received 0.7 cm of daily overhead irrigation. Results indicated that weed seedling survival and final biomass decreased as mulch depth increased. Rice hull mulch at depths of 1.3 cm or greater significantly reduced emergence and biomass of both weed species, providing close to 100% control. These findings suggest that rice hull mulch can be successfully applied 2–3 weeks after potting if a minimum depth of 1.3 cm is used, offering growers a flexible and effective non-chemical weed control strategy.

Mississippi State University’s South Mississippi Branch Experiment Station works with the IR-4 project to conduct trials and collect data to facilitate EPA registration of pest management products important in production of specialty crops. During the 2024 growing season, Gemini Granular was evaluated for phytotoxicity and pre-emergent weed control for Eupatorium purpureum ‘Gateway’. Height, percent flowering, and flower number was also recorded. Gemini Granular is 0.40% Prodiamine 0.25% Isoxaben. Eupatorium purpureum ‘Gateway’ liners were transplanted from 50-cell trays into an aged/screened pine bark based medium in 11.4 L containers on June 28, 2024. Medium was amended with sphagnum peat, perlite, a starter dose of 12-6-6 and 15-9-12 controlled release fertilizers. Containers received drip irrigation. Herbicide was applied twice during the season at 6-week intervals with a hand shaker (July 8 and August 20, 2024). Herbicide rates were control (0 lbs./A), 1x (200 lbs./A), 2x (400 lbs./A), or 4x (800 lbs./A). Experimental design was completely random with 10 replications. Data were analyzed in SAS version 9.4 (SAS Institute, Inc., Cary, NC) using PROC GLIMMIX with mean separation using Tukey’s HSD at α = 0.05. Plants exhibited no phytotoxicity, regardless of herbicide rate. Plants receiving Gemini Granular at 200 lbs./A had greater heights compared to the heights of control plants or plants receiving the 2x or 4x herbicide rate. Flower numbers were only reduced for plants receiving the 2x herbicide rate. Flowering percentages ranged from 16.6% for control plants to 5.1% for plants receiving the 2x herbicide rate. In general, weed pressure was low, and there were no differences between treatments for weed number. Gemini Granular applied at 200 lbs./A, the 1x rate, provided effective and safe weed control for Eupatorium purpureum ‘Gateway’.

Variable-rate spray technology allows nursery producers to make applications tailored to crops, reducing pesticide application volume and off-target losses. The objective of this study was to evaluate sub-default rates (default=0.1-0.15 L⸱m-3) for the Smart-Apply intelligent spray control system by comparing two intelligent modes with the conventional, constant-rate. We assessed control of powdery mildew (Erysiphe pulchra and Phyllactinia guttata) on ‘Cherokee Princess’ dogwoods (Cornus florida) in a five-row block. A Jacto A400/850 air-blast sprayer with the Smart-Apply system was used to compare: variable-rate: 0.05 L⸱m-3 rate in either pulse-on or pulse-off mode and a reduced, i.e.,

Crapemyrtle bark scale (CMBS; Acanthococcus lagerstroemiae) is an invasive phloem-feeding insect that diminishes both the aesthetic appeal and economic value of crapemyrtle (Lagerstroemia sp.), the most widely planted flowering tree in the United States. Conventional control methods, including pruning, scrubbing infested bark, and applying systemic or contact insecticides, offer limited effectiveness due to the insect’s waxy covering, cryptic life stages, and prolific reproduction. Additionally, chemical treatments raise concerns about non-target effects and environmental contamination. To facilitate the development of targeted and sustainable control strategies, we are elucidating the molecular mechanisms governing CMBS development. We have assembled a high-quality reference genome and conducted bulk RNA sequencing across multiple life stages. Building on these resources, we now aim to apply single-cell RNA sequencing (scRNA-seq) to resolve cell-type-specific gene expression patterns throughout development. This high-resolution analysis will uncover key regulatory pathways, informing the identification of novel molecular targets for environmentally responsible CMBS management. We will report on the results of these investigations at the meeting.

Commercial pest control companies as well as homeowners are currently searching for alternatives to the herbicide glyphosate due to negative press and changing consumer preferences. These non-selective alternatives are almost exclusively contact-action herbicides (no systemic activity) and the most common options (diquat, pelargonic acid, acetic acid, plant oils, etc.) have been shown to be effective on annual weeds when label directions are followed. However, labels on individual products often recommend a wide range of application rates (concentrations of the herbicide) and application volumes depending upon weed size, creating confusion for users in terms of what rate and/or application volume is needed for optimal control while keeping costs low. The objective of this research was to evaluate four glyphosate alternatives (acetic acid, caprylic capric acid, diquat, and pelargonic acid) at both high and low labeled application rates and at three different application volumes including 50, 100, and 200 gallons per acre (1.2, 2.3, and 4.6 gallons per 1,000 ft2) to determine how efficacy differed based on these different treatment variables. Two weed species including yellow nutsedge (Cyperus esculentus) and garden spurge (Euphorbia hirta) were used for the evaluation to observe differences between an annual broadleaf (spurge) and a perennial sedge species (yellow nutsedge). Plants were allowed to grow for approximately 6 weeks, at which time herbicides were applied. Data collected included visual control ratings at 1, 2, and 4 weeks after treatment (WAT) and shoot weights collected at 5 WAT. Results differed by weed species and herbicide and on different evaluation dates. For yellow nutsedge, application volume was the most common significant main effect with similar control being achieved at both high and low label rates when the higher application volumes were used. For garden spurge, application volume was mostly insignificant with the high rate providing more consistent control regardless of application volume. Results indicate that for larger or perennial weed species, higher application volumes are more critical to success, given that adequate and label rates are used, as they were needed to achieve more thorough coverage to contact more shoot biomass. In contrast, for the smaller prostrate growing garden spurge, rate was most important as thorough coverage was achieved at the lowest application volumes. This research begins to help us better understand these alternative herbicides and develop recommendations for the most effective and efficient use of these products in Florida landscapes.

Tobacco hornworms (Manduca sexta) are among very destructive insects that feed mainly on plants in Solanaceae plants. The larva stage is the most destructive, feeding on leaves and fruits, and as few as one to three insects can cause 100% loss. Damage caused by hornworms to the stem creates an environment for pathogens to grow, which ultimately kills the entire plant. Synthetic pesticides have been most effective in controlling insect pests but are harmful to the environment and humans. Plant-based biopesticides that are biodegradable, affordable, and eco-friendly may be a sustainable option to mitigate the problem. Several plants have been used as insecticides and have successfully controlled several insects. Due to the increasing demand for safe and biodegradable insecticides, there is a growing interest in sustainable pest control measures, and therefore there is a need to increase the number of plant sources to reduce the gap between demand and supply. Industrial hemp is among potential plants with phytocompounds that can be used as an anti-feeding agent against insects. However, little is known about the ability of the hemp phytocompound as an anti-feeding agent against tobacco hornworms. This study aimed to determine the antifeeding properties of industrial hemp extract against tobacco hornworms in vitro. The ethanolic hemp extracts were prepared at 50, 25, 12.5, 6.25, 3.125, and 1.56 mg/ml. Extracts were incorporated into the artificial diet, fourth instar larvae were introduced into the diet and raised in the growth chamber at 27±2°C, 60±10% RH and photoperiod 12:12 hour light/dark for four days. The relative growth rate differed significantly between concentrations. The growth rate was -0.05 g/g/day at 50 mg/ml, indicating insect body shrinkage, and 0.11g/g/day at 25 mg/ml, indicating slow growth compared to the negative control, which increased by 0.19g/g/day. The highest concentration (50mg/ml) inhibited larvae growth by 100%, similar to Malathion, which was used as a positive control in the study, 25mg/ml inhibited growth by 71%, 12.5mg/ml by 59%, 6.25mg/ml by 51%. Furthermore, an antifeedant index of 68% at 50mg/ml and 62% at 25mg/ml was reported. The findings indicate that industrial hemp extract is a strong antifeedant against tobacco hornworms and, therefore, a strong source of insecticide to control the insect, and thus, a potential contribution to sustainable agriculture.