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.,
Lloyd Nackley is a plant ecologist who applies a systems approach to improve nursery and greenhouse management. Nackley's research program at Oregon State University focuses on addressing four challenges facing nursery and greenhouse production in Oregon: irrigation application, pest... Read More →
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.
