Chemical Control Strategies Research Articles

Potential of Small Molecules Piperidine and Pyrrolidine Against Copper-Resistant Xanthomonas perforans, Causal Agent of Bacterial Spot of Tomato.

Bacterial spot of tomato (BST), caused by Xanthomonas perforans, is an economically important disease of tomatoes in Florida. Due to the heavy reliance on copper-based bactericides for control of BST, copper-resistant strains of X. perforans are widely distributed in Florida, leading to reduced efficacy of copper-based bactericides for disease control. There is a need for alternative chemical control strategies to effectively manage this disease in tomato production. In this study, two small molecules, piperidine and pyrrolidine, were evaluated for their efficacy against the copper-resistant X. perforans strain GEV 485 in laboratory, greenhouse, and field experiments. In in vitro experiments, piperidine and pyrrolidine at concentrations as low as 2 mg/L and 16 mg/L, respectively, significantly (P<0.001) reduced bacterial populations within 4 h of incubation compared to the untreated control, while Kocide 3000, the grower copper-based bactericide standard, at 0.9 g/L and 2.1 g/L (full label rate) did not significantly reduce bacterial populations. When tested as foliar sprays in the greenhouse, pyrrolidine at 128 mg/L significantly (P <0.001) reduced disease severity compared to the untreated control, with an equivalent efficacy to Kocide 3000 (copper hydroxide at 2.1 g/L). Kocide 3000 at 1.0 g/L, in combination with piperidine at 64 mg/L and pyrrolidine at 64 and 128 mg/L significantly improved the efficacy in disease control compared to untreated controls and Kocide 3000 at 1.0 g/L alone. In field trials, both small molecules demonstrated equivalent or superior efficacy to ManKocide (copper hydroxide + mancozeb) against X. perforans compared to the untreated control. This study demonstrated for the first time the potential of piperidine and pyrrolidine for controlling bacterial spot of tomato.

Thiacloprid-silica nano-delivery system enhances toxicity against Aphis gossypii and improves non-target biosafety

Nanotechnology aligns with the requirements of sustainable development of agriculture, and nano-pesticides offer a promising approach to controlling agricultural pests and increasing productivity. Non-target predators also play a crucial role in pest controls and enhancing the efficacy of pesticide on target organisms. Reducing the toxicity of pesticides to non-target organisms is key to of coordinating chemical control and biological control methods. Therefore, it is essential to assess the toxicity of nano-pesticides on non-target predators. In this study, a carbon dots-doped mesoporous silica nano-delivery system (Thi@CD-MSN) was successfully developed using CD-MSN as carrier material and thiacloprid (Thi) as a model pesticide. The results demonstrated that the synthesized Thi@CD-MSN exhibited a relatively high loading efficiency (33.58%). Laboratory bioassay experiments revealed that Thi@CD-MSN demonstrated effective insecticidal activity (LC50 = 21.67 mg/L) in controlling Aphis gossypii Glover. Besides, the acute toxicity of Thi@CD-MSN on Chrysoperla pallens larvae was significantly lower than that of Thi, as was its toxicity to 4T1 cells. These findings suggest that CD-MSN can serve as an ecological safety carrier for pesticide delivery, improving the effective utilization of Thi while reducing the risks to non-target predators. These results are essential for comprehending the effects of nano-pesticides on non-target predators, providing informative data for implementing biological and chemical control strategies. It strengthens the safety evaluation of nano-pesticides.

Fungicide Sensitivity and Non-Target Site Resistance in Rhizoctonia zeae Isolates Collected from Corn and Soybean Fields in Nebraska.

Rhizoctonia zeae was recently identified as the major Rhizoctonia species in corn and soybean fields in Nebraska and was shown to be pathogenic on corn and soybean seedlings. Fungicide seed treatments commonly used to manage seedling diseases include prothioconazole (demethylation inhibitor), fludioxonil (phenylpyrrole), sedaxane (succinate dehydrogenase inhibitor), and azoxystrobin (quinone outside inhibitor; QoI). To establish the sensitivity of R. zeae to these fungicides, we isolated this pathogen from corn and soybean fields in Nebraska during 2015 to 2017 and estimated the relative effective concentration for 50% inhibition (EC50) of a total of 91 R. zeae isolates from Nebraska and Illinois. Average EC50 for prothioconazole, fludioxonil, sedaxane, and azoxystrobin was 0.219, 0.099, 0.078, and > 100 µgml-1, respectively. In planta assays showed that azoxystrobin did not significantly reduce the disease severity on soybean (P > 0.05). The cytochrome b gene of R. zeae did not harbor any mutation known to confer QoI resistance and had a type-I intron directly after codon 143 suggesting that a G143A mutation is unlikely to evolve in this pathogen. For prothioconazole, fludioxonil, and sedaxane, EC50 of isolates did not differ significantly among years of collection (P > 0.05) and their single discriminatory concentrations were identified as 0.1 µgml-1. This is the first study to establish non-target site resistance of R. zeae to azoxystrobin and the sensitivity of R. zeae to commonly used seed treatment fungicides in Nebraska. This information will help to guide strategies for chemical control of R. zeae and monitor sensitivity shifts in future.

Dual RNA sequencing during Trichoderma harzianum-Phytophthora capsici interaction reveals multiple biological processes involved in the inhibition and highlights the cell wall as a potential target.

Phytophthora capsici is a destructive oomycete pathogen, causing huge economic losses for agricultural production. The genus Trichoderma represents one of the most extensively researched categories of biocontrol agents, encompassing a diverse array of effective strains. The commercial biocontrol agent Trichoderma harzianum strain T-22 exhibits pronounced biocontrol effects against many plant pathogens, but its activity against P. capsici is not known. T. harzianum T-22 significantly inhibited the growth of P. capsici mycelia and the culture filtrate of T-22 induced lysis of P. capsici zoospores. Electron microscopic analyses indicated that T-22 significantly modulated the ultrastructural composition of P. capsici, with a severe impact on the cell wall integrity. Dual RNA sequencing revealed multiple biological processes involved in the inhibition during the interaction between these two microorganisms. In particular, a marked upregulation of genes was identified in T. harzianum that are implicated in cell wall degradation or disruption. Concurrently, the presence of T. harzianum appeared to potentiate the susceptibility of P. capsici to cell wall biosynthesis inhibitors such as mandipropamid and dimethomorph. Further investigations showed that mandipropamid and dimethomorph could strongly inhibit the growth and development of P. capsici but had no impact on T. harzianum even at high concentrations, demonstrating the feasibility of combining T. harzianum and these cell wall synthesis inhibitors to combat P. capsici. These findings provided enhanced insights into the biocontrol mechanisms against P. capsici with T. harzianum and evidenced compatibility between specific biological and chemical control strategies. © 2024 Society of Chemical Industry.

Safety evaluation and sublethal effect of broflanilide on Aphidius gifuensis.

Ensuring the safety of insecticides to natural enemy insects of pests is crucial for integrating chemical and biological control strategies. Broflanilide, a novel meta-diamide insecticide, exhibits high insecticidal activity against Myzus persicae (Sulzer) (Hemiptera: Aphididae). To integrate chemical and biological control against M. persicae, we assessed the toxicity of broflanilide to Aphidius gifuensis, and evaluated its safety and sublethal effects. The LC10, LC25, and LC50 values of broflanilide against A. gifuensis were 0.733 mg/L, 1.613 mg/L, and 3.852 mg/L, respectively. The selectivity toxicity ratio of broflanilide to A. gifuensis was 1.516, indicating higher toxicity to M. persicae compared to A. gifuensis. The risk quotient of broflanilide to A. gifuensis adults was 6.18. The percent reduction in the emergence of the parasitoid pupae was -1.15, with a risk grade of 1. The sublethal concentration of broflanilide had no significant influence on the intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R0), and mean fecundity (F) of A. gifuensis in the F1 generation. The mean generation time (T) increased by 0.51 days and 0.39 days in the LC10 and LC25 treatments, respectively; the difference between LC10 treatment and the control was significant, while the difference between LC25 treatment and the control was not significant. The results showed that the sublethal concentration of broflanilide did not have a significant inhibitory effect on the population growth of A. gifuensis.

Plant-induced bacterial gene silencing: a novel control method for bacterial wilt disease.

Ralstonia pseudosolanacearum, a notorious phytopathogen, is responsible for causing bacterial wilt, leading to significant economic losses globally in many crops within the Solanaceae family. Despite various cultural and chemical control strategies, managing bacterial wilt remains a substantial challenge. This study demonstrates, for the first time, the effective use of plant-induced bacterial gene silencing against R. pseudosolanacearum, facilitated by Tobacco rattle virus-mediated gene silencing, to control bacterial wilt symptoms in Nicotiana benthamiana. The methodology described in this study could be utilized to identify novel phytobacterial virulence factors through both forward and reverse genetic approaches. To validate plant-induced gene silencing, small RNA fractions extracted from plant exudates were employed to silence bacterial gene expression, as indicated by the reduction in the expression of GFP and virulence genes in R. pseudosolanacearum. Furthermore, treatment of human and plant pathogenic Gram-negative and Gram-positive bacteria with plant-generated small RNAs resulted in the silencing of target genes within 48 hours. Taken together, the results suggest that this technology could be applied under field conditions, offering precise, gene-based control of target bacterial pathogens while preserving the indigenous microbiota.

Mosquito suppression via Filippov incompatible insect technique

Mosquito-borne diseases persist as a global health challenge despite ongoing control efforts, necessitating the exploration of alternative control approaches. This research proposes a Filippov incompatible insect technique (IIT) model with a threshold policy control for suppressing mosquito population. The model implements biological and chemical control strategies only when wild mosquito density surpasses an economic threshold. The biological strategy involves releasing Wolbachia-infected male mosquitoes, offering advantages such as a shortened lifespan and disease blocking. Simultaneously, moderate insecticide and larvicide spraying serve as a chemical approach to expedite the control process. The model provides economic advantages by minimizing control costs and environmental benefits through the integration of biological strategies, thus reducing reliance on chemicals. By employing Filippov's convex method, we identify necessary conditions for the existence of sliding segments and determine the dynamics of the switching line. Theoretical analysis reveals the model's long-term dynamics, including sliding bifurcations, pseudo-equilibria, and their stability. The model exhibits boundary equilibrium bifurcations and transcritical bifurcations in both free and controlled systems. Varying threshold values significantly impact the control outcomes effectiveness. The main findings demonstrate that integrated strategies efficiently decrease the population density of wild mosquitoes.

Point mutations in the voltage-gated sodium channel gene conferring pyrethroid resistance in China populations of the Dermanyssus gallinae.

Dermanyssus gallinae, the poultry red mite (PRM), is a worldwide ectoparasite posing significant economic challenges in poultry farming. The extensive use of pyrethroids for PRM control has led to the emergence of pyrethroid resistance. The objective of this study is to detect the pyrethroid resistance and explore its associated point mutations in the voltage-gated sodium channel (VGSC) gene among PRM populations in China. Several populations of D. gallinae, namely CJF-1, CJP-2, CJP-3, CSD-4 and CLD-5, displayed varying degrees of resistance to beta-cypermethrin compared to a susceptible field population (CBP-5). Mutations of VGSC gene in populations of PRMs associated with pyrethroid resistance were identified through sequencing its fragments IIS4-IIS5 and IIIS6. The mutations I917V, M918T/L, A924G and L925V were present in multiple populations, while no mutations were found at positions T929, I936, F1534 and F1538. The present study confirmed the presence of extremely high levels of pyrethroid resistance in PRM populations in China, and for the first time detected four pyrethroid resistance mutations in the VGSC gene. Identifying pyrethroid resistance in the field population of PRM in China can be achieved through screening for VGSC gene mutations as an early detection method. Our findings underscore the importance of implementing chemical PRM control strategies based on resistance evidence, while also considering the management of acaricide resistance in the control of PRMs. © 2024 Society of Chemical Industry.

A comprehensive review of Pseudocercospora fruit and leaf spot (angular leaf spot): Current status, advances and future directions for sustainable citrus production

AbstractPseudocercospora fruit and leaf spot (PFLS), also known as angular leaf spot of citrus, is a devastating fungal disease that poses a significant threat to citrus production, profitability and food security in sub‐Saharan Africa and the Arabian Peninsula. In the present review, we explore current knowledge regarding PFLS management initiatives, including cultural practices, chemical control strategies and biological interventions. Furthermore, this review highlights the challenges faced in controlling PFLS and emphasizes the urgent need for sustainable and cost‐effective solutions to combat the disease. We discuss recent advancements and emerging prospects in understanding PFLS, including novel approaches for disease management and the potential for developing resistant citrus cultivars through breeding programmes or genetic modification. By synthesizing existing research findings and identifying gaps in knowledge, this review aims to provide a comprehensive understanding of PFLS and its impact on food security. We emphasize the importance of collaborative efforts, knowledge exchange and developing integrated disease management strategies to control PFLS and mitigate its detrimental effects on citrus production and farmers' livelihoods in affected regions.

Agricultural Practices for Biodiversity Enhancement: Evidence and Recommendations for the Viticultural Sector

Agricultural expansion and intensification worldwide has caused a reduction in ecological infrastructures for insects, herbaceous plants, and vertebrate insectivores, among other organisms. Agriculture is recognized as one of the key influences in biodiversity decline, and initiatives such as the European Green Deal highlight the need to reduce ecosystem degradation. Among fruit crops, grapes are considered one of the most intensive agricultural systems with the greatest economic relevance. This study presents a compilation of management practices to enhance biodiversity performance, which applies generally to the agricultural sector and, in particular, to viticulture, concerning the diversity of plants, semi-natural habitats, soil management, and the chemical control strategies and pesticides used in agricultural cultivation. Through a critical review, this study identifies a set of recommendations for biodiversity performance and their corresponding effects, contributing to the dissemination of management options to boost biodiversity performance. The results highlight opportunities for future investigations in determining the needed conditions to ensure both biodiversity enhancement and productive gains, and understanding the long-term effects of innovative biodiversity-friendly approaches.

Integrated parasite management (IPM) and the pasture ecosystem: Optimizing outcomes for cattle, insect biodiversity, and soil health

Concerns over the negative environmental impacts of livestock parasiticide treatments and the widespread development of resistance has precipitated a move towards integrated parasite management (IPM). However, within the pasture ecosystem management strategies are likely to impact multiple processes in complex ways. This study investigates the impacts of IPM strategies on pest flies, gastrointestinal nematode (GIN) parasites, beneficial dung insects, and soil health. Twenty-nine grazing dairy farms participated in the study, representing different chemical and nonchemical parasite management and grazing strategies (continuous, rotational, or management intensive rotational (MIG)). Cattle managed using rotational grazing and MIG had significantly lower FEC than continuously grazed cattle. Farms using chemical parasiticides had significantly fewer pest flies, however farms releasing parasitoid wasps as biological control also had reduced abundances. Dung inhabiting beetle abundance was significantly correlated with reduced pest flies and GIN. Beneficial insects were negatively impacted on farms that used parasiticides. Continuously grazed pastures had higher beneficial insect abundances only on farms that did not use chemical parasiticides. Pastures managed under MIG had lower soil bulk density and higher active carbon compared to continuous grazing. There were positive associations between soil health and tunneling dung insects (Onthophagus spp. dung beetles). Finding optimal strategies will be context dependent, however the results of this study indicate that grazing strategies can control gastrointestinal parasites and improve soil health outcomes, natural enemies such as parasitoid wasps and dung inhabiting beetles can suppress pest fly populations, and the impacts of chemical control strategies may be mitigated through thoughtful implementation.

Resistance to natural tick infestation varies with age and coat and hair traits in a tropically adapted beef cattle breed

Rhipicephalus (Boophilus) microplus causes considerable livestock production losses. Knowledge of the traits that influence tick resistance contributes to the development of breeding strategies designed to improve herd productivity. Within this context, this study evaluated the resistance of Caracu, a tropically adapted cattle breed, to R. microplus. Tick count, hair length, coat thickness, and coat color were evaluated in 202 naturally tick-infested females (cows and heifers) over a period of 18 months. Blood samples were collected from all animals during the winter season for hematological analysis. Data were analyzed using Pearson correlations, generalized linear models, and principal component analysis. Correlation coefficients of tick count with coat color, coat thickness, and hair length were estimated within each season. Hematological parameters were only included in the winter season analysis and were analyzed by the restricted maximum likelihood method using log-transformed data. No differences in blood parameters were observed between animals with and without ticks. However, tick count was negatively correlated with erythrocytes (−0.29) and hematocrit (−0.24) and positively correlated with mean corpuscular hemoglobin (0.21) and mean corpuscular hemoglobin concentration (0.25). These findings suggest that higher tick counts lead to a decrease in erythrocytes but also to an increase in the amount of hemoglobin per erythrocyte, which could reduce the damage caused by low erythrocyte levels due to tick hematophagy, delaying or preventing anemia. Although tick infestation on pasture was demonstrated by the infestation of all staff members during herd management, none of the animals exhibited high tick counts, providing evidence of resistance of Caracu animals to R. microplus. Tick infestation was influenced by age class (cows > heifers), season (spring and summer > fall and winter), coat thickness (>1.5 mm > <1.5 mm), and hair length (>6 mm > <6 mm). Three components were extracted by principal component analysis, which accounted for 69.46% of data variance. The findings of this study will contribute to the development of efficient strategies aimed at reducing economic losses due to tick infestation and could be applied in animal breeding to select for tick resistance traits, reducing chemical control strategies and consequently improving sustainable livestock production.

Thrips Species Composition in Ontario Greenhouse Floriculture: Innovative Identification Tools and Implications for Integrated Pest Management.

Proper species identification is the keystone of successful integrated pest management (IPM). However, efforts to identify thrips species in Canadian greenhouses have not been formally made since the 1980s. In response to recent increases in crop damage, we sampled thrips communities from eight commercial floriculture greenhouses in the Niagara region (Ontario, Canada) from May until August 2016. Selected sites were revisited in 2017, 2018, and 2019 to determine changes in species composition over time. Western flower thrips (Frankliniella occidentalis (Pergande)), along with onion thrips (Thrips tabaci Lindeman), constituted the majority of species found. Other pest species (less than 8% of specimens across all sampling years) included poinsettia thrips (Echinothrips americanus Morgan), chrysanthemum thrips (Thrips nigropilosus Uzel), and Frankliniella fusca (Hinds). Further investigations of thrips outbreaks in Ontario from 2016 to 2023 revealed other important species, including Thrips parvispinus (Karny), Hercinothrips femoralis (Reuter), and Scirtothrips dorsalis Hood. The current biocontrol strategies used in Ontario floriculture crops for western flower thrips do not adequately control onion thrips or other thrips pests in ornamental crops, making identification a fundamental step in determining whether biocontrol or chemical control strategies should be implemented. However, traditional taxonomic keys are inaccessible to non-specialists due to their technical difficulty. Using the data gathered in these surveys, we developed a simplified, illustrated identification key for use by growers and IPM consultants.

Increasing the tolerance of Trichoderma harzianum T-22 to DMI fungicides enables the combined utilization of biological and chemical control strategies against plant diseases

Demethylase inhibitors (DMIs) targeting CYP51 proteins in fungi are often used for plant disease management. Trichoderma harzianum, a widely used biocontrol agent, however, is sensitive to DMIs. This negates their combined use as a strategy in practices. Increasing the tolerance of T. harzianum to DMIs represents a feasible solution to this problem. In this regard, the overexpression of a CYP51B variant in Mycosphaerella graminicola (MgCYP51B-v) conveys increased tolerance to DMIs. Molecular docking indicated a distinct decrease in the affinity of MgCYP51B-v with DMIs. Since CYP51B proteins are conserved in M. graminicola and T. harzianum, we attempted to increase DMI tolerance in T. harzianum by heterologously expressing MgCYP51B-v. A series of T. harzianum mutants were obtained that were able to develop colonies on tebuconazole-amended medium. Two representative mutants were selected for further studies that confirmed that they were resistant to tebuconazole with resistance factors (RFs) of approximately 10.0. The mutants maintained a similar level of resistance after ten rounds of subculture without fungicide, indicating that the fungicide resistance was stably inherited. The mutants also exhibited increased tolerance to other DMIs, including metconazole, ipconazole, hexaconazole, and prochloraz. Further assessment indicated that the DMI resistance in the mutants did not have any impact on their fitness. The improved compatibility between T. harzianum and DMIs enables the utilization of a combined strategy in which these disease control agents are used together. Such a strategy has the potential to provide synergistic disease control and prevent or delay the development of fungicide resistance.

Bacteria-based Sodium Alginate Formulation to Control Toxic Microcystis Blooms

Cyanobacterial bloom formation in freshwaters is a major socio-economic and health concern across the globe. Presently used chemical and physical control strategies are inefficient in complete removal of blooms and chemical application often lead to secondary pollution in water. Hence, the current study aimed to develop a bacteria-based formulation to control toxic bloom-forming Microcystis aeruginosa in freshwaters. Two bacterial strains, Exiguobacterium acetylicum and Pseudomonas previously isolated from Sri Lankan freshwaters and characterized for M. aeruginosa cell lysis and their microcystin (MC) toxin degradation were used in the study. Initially, suitability of bacterial strains to develop into solid formulations was evaluated through biofilm formation, antibiotic sensitivity and strain compatibility. Both strains formed biofilms on the surface of microtiter plates indicating their ability to attach and colonize on solid surfaces. The multiple antibiotic resistance indices for both strains were below the threshold risk level (0.2) against the seven tested classes of antibiotics. This result indicates that there is a low risk in introducing these bacterial strains to the natural environment. Further, plate assay showed that the two strains were compatible to stay together showing no antagonistic effect on the growth of each other. Having fulfilled all three criteria tested, the two strains were immobilized into beads (~5 mm) prepared from sodium alginate at 1:1 ratio of 1×108 cells/mL bacterial inoculum. Different weights (1.0, 2.0, 3.0 g) of bacteria-immobilized beads were enclosed in sachets made with Cambrella synthetic fabric. They were introduced to M. aeruginosa grown in BG-11 medium (OD=0.2, 730 nm) and kept at 26 °C. During incubation, growth stimulation of M. aeruginosa was visually observed in 1.0 and 2.0 g beads-containing cultures, whereas, gradual discoloration of colonies was observed with 3.0 g of beads. Microscopic observations also proved complete disintegration of M. aeruginosa colonies and lysis of cells in discolored cultures. After 15 days, M. aeruginosa cell lysis was estimated as a measure of chlorophyll degradation. The highest (8.4%) cell lysis was observed in cultures containing 3.0 g of beads. This indicates that bacteria cell lysis activity depends on the load of bacteria-immobilized beads. Degradation of MC toxin was estimated by enzyme-linked immunosorbent assay. The highest (57.6%) MC degradation was observed in cultures with 3.0 g of beads after 15 days of incubation. The efficiency of bacteria release from beads was tested by placing sachets in sterilized water. At 15 days, bacterial count in water was x107 CFU/mL, with all loadings of immobilized-bacteria indicating highly efficient bacteria release from the formulation. In conclusion, this study highlights that bacteria-based sodium alginate formulations can be made as a source of inoculum to control M. aeruginosa growth and MC degradation. &#x0D; Keywords: Bacteria-based formulations, Cell lysis, Microcystis blooms, Microcystin

Compatibility of two novel insecticides dimpropyridaz and Beauveria bassiana PPRI 5339 with the beneficial insect Nesidiocoris tenuis (Reuter)

Nesidiocoris tenuis is a zoophytophagous insect widely used commercially as a biological control agent against different pests and crops under greenhouse conditions. For a successful Integrated Pest Management (IPM) strategy, it is crucial to know the compatibility of available and new crop protection products with biological control agents. The aim of this study was to evaluate and classify the lethal and sublethal effects of different crop protection products on the biological control agent N. tenuis, including the novel insecticides dimpropyridaz and Beauveria bassiana strain PPRI 5339, in accordance with the International Organisation for Biological and Integrated Control (IOBC) directives. Dimpropyridaz, B. bassiana PPRI 5339, the adjuvant fatty acid esters and the combination of B. bassiana PPRI 5339 with the adjuvant have been classified as harmless (IOBC 1 < 25% of mortality and beneficial capacity). The evaluation of reproduction and capacity for increase (rc) showed no significant sublethal effects between the previous compounds and the untreated control. Flupyradifurone, sulfoxaflor, and dimethoate were classified as harmful (IOBC 4 > 75% of mortality and beneficial capacity). The compatibility of these two new products (dimpropyridaz and B. bassiana PPRI 5339) with Nesidiocoris tenuis is of great importance because it adds new tools to be used in IPM programmes in which chemical and biological control strategies are used together.

Chemical Control Strategies for Managing Froghopper (Spittle Bug) Populations: Current Insights and Future Directions

Chemical Control Strategies for Managing Froghopper (Spittle Bug) Populations: Current Insights and Future Directions

Enhancing Sugar Beet (Beta vulgaris L.) Yield and Quality: Evaluating the Efficiency of Chemical and Mechanical Weed Control Strategies

Weeds exert a pronounced influence on the sugar beet yield, leading to the potential for substantial reductions in agricultural productivity. In pursuit of addressing this issue, two experiments were conducted at the Faculty of Agriculture in Giza, Egypt, during the winter seasons of 2020/2021 and 2021/2022 to investigate the efficacy of various pre- and post-herbicides applied differently in active ingredient percentages, forms, and on weed target types, and mechanical weed treatments on weed traits and sugar beet crop performance. (1) In this context, five herbicidal treatments, including pre-emergence (S-Metoachlor) and post-emergence applications of Betanal Max Pro (Desmedipham 4.7% + Ethofumesate 7.5% + Lenacil 2.7% + Phenmedipham 6%), Tegrospecial (Desmedipham 20% + Phenmedipham 20%) for total annual weeds, C Factor (Haloxyfop-R-Methyl 7.5% + Fluazifop-p-putyl 15%), and Clictar (Clethodium 24%) for grassy weeds, were assessed alongside mechanical weeding and a weedy check (control). (2) The evaluations encompassed growth parameters, juice quality, and beet yields to comprehensively assess the treatment effects. (3) Notably, weed control measures, especially regarding three total annual weeds herbicides and the cultivation when using both grassy weed herbicides, consistently produced the highest improvements in sugar beet root’s fresh and dry weights, root dimensions, sucrose content, purity, sugar recovery, as well as the root and recoverable sugar yields, across both seasons. (4) However, it is important to note that the application of Clethodium 24% and Haloxyfop-R-Methyl 7.5% + Fluazifop-p-putyl 15% resulted in elevated levels of sodium, potassium, amino nitrogen, impurities, and sucrose loss to molasses. These findings underscore the substantial influence of herbicide use and mechanical weeding on sugar beet’s growth, juice quality, and yield, with S-Metoachlor, Desmedipham 20% + Phenmedipham 20% and Desmedipham 4.7% + Ethofumesate 7.5% + Lenacil 2.7% + Phenmedipham 6%—showing promise as effective weed control options, albeit with certain associated drawbacks.

Evaluation of Fungicides as Protective and Curative Treatments against Canker Disease of Eucalyptus urograndis Caused by Chrysoporthe deuterocubensis in Malaysia

Over the years, Eucalyptus plantations have rapidly expanded in Sarawak, Malaysia, accounting for 19% of the total forest plantation area. In a routine forest health surveillance conducted in 2022 at Sarawak, Malaysia, tree stands of Eucalyptus urograndis (Eucalyptus grandis × Eucalyptus urophylla hybrid) were detected with symptoms of stem canker disease caused by Chrysoporthe infection. Given the limited information on the chemical control of Chrysoporthe stem canker disease, there is a growing need to develop effective chemical control strategies to protect and cure Chrysoporthe infection on E. urograndis trees. Therefore, this study aimed to identify the causal pathogen of this stem canker disease in 7-year-old E. urograndis trees in Sarawak, Malaysia, and evaluate the efficacy of various fungicides as curative or protectant treatments on canker infection using artificial inoculation methods. Fungal isolates were first collected and subjected to molecular identification and pathogenicity analysis. Then, in vitro efficacy tests were evaluated using five licensed fungicides: thiram, prochloraz manganese chloride, copper hydroxide, dimethomorph, and mancozeb. Subsequently, the performance of these fungicides was assessed through preventive and curative field experiments on 10-year-old E. urograndis trees using the artificial inoculation technique. Based on the morphological and phylogenetic analysis of the ITS1/ITS4, β-tubulin 2 (BT2), and the combined ITS1/ITS4 and BT2 sequences extracted from 20 fungal isolates, Chrysoporthe deuterocubensis was identified as the causal pathogen of the canker disease, with isolate CHRY18 recording the highest virulence. The in vitro efficacy tests showed that prochloraz manganese chloride achieved 100% inhibition against C. deuterocubensis at 1.0 mg/mL. In the preventive experiment, thiram significantly inhibited C. deuterocubensis infection, yielding the shortest lesion length (19.40 mm) compared to the non-treated control (47.48 mm) at 20 weeks post-inoculation. In the curative experiment, a significant reduction of 54.7% in lesion length was observed in inoculated symptomatic trees after 20 weeks of post-fungicide treatment with copper hydroxide. In conclusion, this study demonstrated prochloraz manganese chloride, thiram, and copper hydroxide as effective chemical controls of C. deuterocubensis stem canker on E. urograndis.

Control of two-spotted spider mite, Tetranychus urticae, on strawberry by integrating with cyetpyrafen and Phytoseiulus persimilis

The two-spotted spider mite (TSSM, Tetranychus urticae Koch) is a significant agricultural pest, particularly in strawberries. Management of TSSM has traditionally relied on synthetic acaricides, but to mitigate dependency on these chemicals, the control of TSSM on strawberry is often combined with biological control measures and chemical control strategies. The predatory mite, Phytoseiulus persimilis, is a promising biological control agent, preying on all TSSM developmental stages. In this study, we examined the toxicity of six common acaricides on TSSM and P. persimilis, and cyetpyrafen was selected due to its highest relative toxicity value. Then, we examined the compatibility of cyetpyrafen with P. persimilis for TSSM management on strawberries. The results suggested that cyetpyrafen revealed no substantial differences in prey consumption or longevity when compared to the control, though minor effects on the development durations of protonymphs and deutonymphs were noted in the subsequent generation. Additionally, cyetpyrafen's toxicity on key pollinators, such as Apis mellifera and Bombus terrestris, was found to be low. Thus, an integrated strategy combining cyetpyrafen (0.83 mg/L) with P. persimilis (predator–prey ratio of 1:30) was examined under laboratory and field conditions. Laboratory trials demonstrated a reduction in mites per leaf from 32.72 to 14.50 within 3 days, correlating to a 70.23% control efficiency. This efficacy increased to 96.04% by day 9 and was sustained until the experiment concluded on day 27. Field trials similarly showed a reduction in TSSM from 53.93 to 9.63 mites/leaf by day 6, achieving an 83.64% control efficiency, and culminated in a 98.46% reduction by day 10. These findings suggested that an integrated approach utilizing cyetpyrafen in conjunction with P. persimilis can be an effective alternative for TSSM management on strawberry plants.