Fungicide Application Research Articles

Yield and Growth Response of Selected Potato Cultivars to Different Mulch and Fungicide Applications, and Various Localities Under Rainfed Conditions

AbstractThere is a stark yield gap between sub-Saharan African (SSA) potato productivity compared to other regions, leading to food security challenges. Hence, there is an immediate need to improve SSA potato yield. Research trials were under smallholder settings to determine effective management practices on the integration of selected potato cultivars, fungicides, mulch application, and different localities. Tested factors mulch application (mulch, not mulch), fungicide (sprayed and unsprayed) and different potato cultivars (Electra, Mondial, Panamera, and Sababa) were laid in a randomized complete block design in under five localities (Gobizembe, Hlathikhulu, Mbalenhle, Mbhava, and Stezi), and replicated three times over two consecutive seasons. Data collection included climatic data, emergence, days to flowering, plant height, physiological maturity, stem number yield, and yield components. Integration of Electra, fungicide (sprayed or unsprayed), and mulch application (mulch or not mulch) under humid, low atmospheric water demand, dominated by sandy soils and high-altitude locality had higher yields with the highest of 64.2 t ha−1 and a harvest index of 90.2%. In the locality that is on a south-facing slope, with the lowest altitude, clayed soils had the lowest yield of 13.4 t ha−1 from Mondial cultivar under unsprayed and no mulch. Electra cultivar showed consistent performance under different practices and yielded more across localities. Hence, it is recommended that effective management practices such as Electra together with fungicide (spraying or unsprayed) and mulch (mulch or not mulch) can be adopted to increase potato yield under rainfed conditions.

Synergistic growth suppression of Fusarium oxysporum MLY127 through Dimethachlon Nanoencapsulation and co-application with Bacillus velezensis MLY71

Fusarium oxysporum is a destructive plant pathogen with robust survival mechanisms, complicating control efforts. This study aimed to develop nanoformulated fungicides, screen antagonistic bacteria, and evaluate their combined efficacy. A novel self-emulsifying nanoemulsion (DZW) was formulated using zein and benzaldehyde-modified wheat gluten (BgWG) as carriers for dimethachlon (DTN). The preparation process optimized material ratios and emulsification techniques. Concurrently, antagonistic bacterial strains against F. oxysporum were screened via the plate standoff method, identifying Bacillus velezensis MLY71 as both antagonistic and compatible with DTN. The DZW nanoemulsion achieved a particle size of 93.22 nm, an encapsulation efficiency (EE) of 90.57%, and a DTN loading capacity (LC) of 67.09%, with sustained release over 96 h. The combination of DTN (0.04 mg·mL⁻¹) and B. velezensis MLY71 (1 × 10⁴ CFU·mL⁻¹) achieved a 76.66% inhibition rate against F. oxysporum MLY127, 1.71 times greater than DTN alone, indicating significant synergy. At a DTN concentration of 0.20 mg·mL⁻¹, the combination of DZW and MLY71 showed a synergy coefficient of 1.33. This synergy was also observed in soil environments, indicating its adaptability for controlling soil-borne pathogens. As sustainable management continues to gain attention in agricultural disease control, this study offers a promising strategy for achieving higher efficacy with the same fungicide dose or satisfactory control with reduced fungicide application. The excellent drug-loading performance of BgWG also expanded the applications of the wheat by-product gluten.

Control of Apple Scab in Commercial Orchards Through Primary Inoculum Management

Apple scab, caused by Venturia inaequalis, is one of the most important diseases in apples in all production regions and its sustainable control is still a challenge. The aim of this work was to optimize the control of apple scab through different environmentally friendly inoculum management strategies, specifically the removal of fallen leaves in winter and the treatment of ground leaves with the biological agent Trichoderma asperellum (T34 BIOCONTROL®) to inhibit or prevent inoculum development in commercial orchards. The results obtained from 4 years of trials in commercial orchards demonstrated that the combination of fungicide treatments and leaf litter management, particularly through aspiration, significantly reduced the development of apple scab in comparison with strategies commonly used by growers that are based solely on fungicide application. Both the incidence and severity of the disease in leaves and fruit decreased by over 90% when inoculum management and fungicide treatments were combined. These results highlight that reducing the source of inoculum by removing fallen leaves is an effective strategy that complements fungicide or biological control agent applications. In conclusion, combining eco-friendly strategies with standard fungicides and monitoring environmental conditions can help to reduce the frequency of phytosanitary applications, ultimately contributing to the goal of minimizing their use in the control of apple scab.

Exploring the Potential Fungicidal Applications of a Cu(II) Complex with Schiff Base and Carboxylates against Fusarium equisetum

Exploring the Potential Fungicidal Applications of a Cu(II) Complex with Schiff Base and Carboxylates against <i>Fusarium equisetum</i>

The Mechanisms of Developing Fungicide Resistance in Fusarium graminearum Causing Fusarium Head Blight and Fungicide Resistance Management.

Fusarium head blight (FHB), primarily caused by Fusarium graminearum, is one of the economically significant diseases in small grains. FHB causes severe damage to wheat production and grain quality. Several management strategies have been developed to control FHB, and chemical control through fungicides plays a significant role. Although fungicides have effectively controlled F. graminearum in the field, the continuous exposure causes a selection pressure in the pathogen population towards fungicide resistance. Several studies have identified fungicide-resistant F. graminearum isolates and fungicide-resistance mechanisms. Although new fungicides with a new mode of action can be introduced into the market, developing a new fungicide is time-consuming, and extra efforts are needed for testing, approvals, and registrations. Therefore, it is essential to strategize the methods to delay the fungicide resistance. This review focuses on the impact of several fungicide applications currently used on FHB, focusing on Fusarium graminearum, the status of the fungicide sensitivity for fungicide classes, the resistance mechanisms against fungicides, and the mitigation strategies to delay the development of fungicide resistance in the pathogen population. Studying the fungicide resistance mechanisms and the mitigation strategies will be helpful in the future to use the available fungicides against F. graminearum without losing its effectiveness.

DESEMPENHO DA PRODUTIVIDADE DE MILHO A PARTIR DE APLICAÇÃO DE FUNGICIDA EM DIFERENTES ESTÁGIOS FENOLÓGICOS

Corn (Zea mays L.) is a crucial crop in terms of global production and economic value, but it is susceptible to fungal diseases such as common rust (Puccinia sorghi) and cercosporiosis (Cercospora zeae-maydis), which can reduce grain production and quality. Effective control of these diseases is vital for food security and agricultural economy. Proper management of corn fungal diseases depends on the plant's phenological stages, from planting to grain maturity. The application of fungicides at strategic moments during the plant's life cycle is essential to prevent infections and reduce disease impact. A study conducted in Patos de Minas, Minas Gerais, during 2023, evaluated the effect of fungicide application at different phenological stages of corn on final productivity. The results showed that fungicide application at multiple phenological stages (V4, V8, and VT) resulted in greater above-ground height, lower severity of fungal diseases, higher productivity, and uniform stalk diameter compared to the control treatment. This integrated disease management method proved effective in protecting plants against fungal diseases, promoting healthier and more vigorous growth, and increasing final corn productivity. These findings highlight the importance of fungicide application at strategic moments in the corn development cycle to maximize productivity and promote more efficient and sustainable agriculture.

Droplet Digital PCR: A New Molecular Method to Detect G1105S/V Mutations in Plasmopara viticola CesA3 Gene.

Plasmopara viticola is the causal agent of Grapevine Downy Mildew (GDM), which is a devastating disease of grapevines in humid temperate regions. The most employed method for protecting grapevines against GDM is the application of chemical fungicides. In Spain, Carboxylic Acid Amides (CAAs) are a fungicide group currently utilized in GDM control. In P. viticola, resistance to CAAs is conferred by G1105S and G1105V mutations in the CesA3 gene. Droplet digital polymerase chain reaction (ddPCR) is an innovative technique that combines PCR and droplet microfluidics to disperse the sample into thousands of water-in-oil droplets in which an amplification reaction is individually performed. In this study, we set up a ddPCR protocol to quantify S1105 and V1105 mutations conferring resistance to CAAs in P. viticola. The optimal PCR conditions were established, and the sensitivity and precision of the protocol were assessed. Four P. viticola populations coming from commercial vineyards in northern Spain were analyzed, and different allele frequencies were found in the analyzed samples corresponding to the different fungicide management strategies, ranging from 7.72% to 100%. Knowing the level of mutated alleles allows for designing resistance management strategies suited for each location. This suggests that similar ddPCR assays could be developed for studying mutations implicated in fungicide resistance in other fungicide groups and plant pathogens.

Characterization of autochthone biological control agents for pear protection against the brown spot of pear disease caused by Stemphylium vesicarium

AbstractStemphylium vesicarium is an important phytopathogen for many plant species, that switches between necrotrophic and saprophytic lifestyles. In the last decade, it has severely affected pear production worldwide, causing the so-called brown spot of pears (BSP), which led to the replacement of several pear orchards in northern Italy with consequent important economic losses. In the field, the management of the disease still relies on fungicide application, though several resistant genotypes of the pathogen emerged through the years. In the present study, three different bacterial species have been isolated from an infected orchard and evaluated as potential biological control agents (BCAs) against a local isolate of Stemphylium vesicarium. Two bacterial isolates belonging to the Bacillus genus demonstrated a significant ability to inhibit S. vesicarium growth in vitro, both through direct antagonism and the emission of volatile organic compounds (VOCs). The cell-free supernatant from one of these isolates exhibited a strong biocontrol activity, particularly through compounds extracted in acidic conditions. The protective effectiveness of the two most promising BCAs was further validated on detached pear fruits infected with S. vesicarium. Overall, the findings suggest that these two BCAs have the potential to be developed into a bio-based alternative to fungicides to control BSP, thus contributing to a more sustainable pear production.

Crop rotation and fungicides impact microbial biomass, diversity and enzyme activities in the wheat rhizosphere

Sustainable crop production systems should promote large and diverse soil microbial communities to enhance biological soil processes rather than depend solely on chemical interventions that include pesticide applications. Crop rotation increases above-ground temporal diversity which, relative to monoculture, usually increases soil microbial diversity. But comparisons between short and long crop rotations that also include pesticide effects are rare. A 5-yr (2013-2017) field study was conducted to investigate crop rotation and fungicide effects on the soil microbiome and activity. There were nine rotations, with or without fungicide applications, that included four 2-yr rotations (wheat preceded by canola, barley, pea, or flax), four 3-yr rotations where barley or canola were added to the 2-yr rotations, and one rotation where canola and wheat were stacked (canola-canola-wheat-wheat). In 2017, soil microbial biomass, composition, diversity and enzyme activities were measured in the rhizosphere of the final wheat crop in each rotation. Fungicides reduced fungal richness (the number of different fungal taxa) in the wheat rhizosphere (e.g., Chao1 indices of 64.0 vs. 79.9) especially in 2-yr rotations, but rotation length/type and the crops that preceded wheat had different effects on different taxa. Two of the three most predominant prokaryotic phyla, Proteobacteriota and Actinobacteriota, responded differently to rotation length: 3-yr rotations enriched the former (27.4% vs. 20.1% relative abundances), but 2-yr rotations enriched the latter (19.9% vs. 28.3% relative abundances). Relative to oilseed crops preceding the sampled wheat, a field pea preceding crop enriched Actinobacteriota (31.7% vs. 24.8% relative abundances) and the most abundant fungal class, Sordariomycetes (39.1% vs. 22.1% relative abundances), in addition to increasing microbial biomass carbon (MBC) and arylsulphatase activity by 33% and 57%, respectively. Correlations of the relative abundances of fungal or prokaryotic genera with β-glucosidase and arylsulphatase activities were similar (both positive or negative), but they were the opposite of correlations with acid phosphomonoesterase, suggesting a close link between C and S cycling. Besides the nutrient cycling implications of these soil microbial characteristics, there is need to study their biological disease control significance.

Microplastic diversity increases the abundance of antibiotic resistance genes in soil

The impact of microplastics on antibiotic resistance has attracted widespread attention. However, previous studies primarily focused on the effects of individual microplastics. In reality, diverse microplastic types accumulate in soil, and it remains less well studied whether microplastic diversity (i.e., variations in color, shape or polymer type) can be an important driver of increased antibiotic resistance gene (ARG) abundance. Here, we employed microcosm studies to investigate the effects of microplastic diversity on soil ARG dynamics through metagenomic analysis. Additionally, we evaluated the associated potential health risks by profiling virulence factor genes (VFGs) and mobile genetic elements (MGEs). Our findings reveal that as microplastic diversity increases, there is a corresponding rise in the abundance of soil ARGs, VFGs and MGEs. We further identified microbial adaptive strategies involving genes (changed genetic diversity), community (increased specific microbes), and functions (enriched metabolic pathways) that correlate with increased ARG abundance and may thus contribute to ARG dissemination. Additional global change factors, including fungicide application and plant diversity reduction, also contributed to elevated ARG abundance. Our findings suggest that, in addition to considering contamination levels, it is crucial to monitor microplastic diversity in ecosystems due to their potential role in driving the dissemination of antibiotic resistance through multiple pathways.

The Effect of Variety and Fungicide Application on Yellow Rust (&amp;lt;i&amp;gt;Pucciniastriiformis&amp;lt;/i&amp;gt;f.sp&amp;lt;i&amp;gt;tritici&amp;lt;/i&amp;gt;) Disease of Bread Wheat (&amp;lt;i&amp;gt;Triticumaestivum&amp;lt;/i&amp;gt;L.) in East &amp;lt;i&amp;gt;Gojjam&amp;lt;/i&amp;gt;, Ethiopia

The study was conducted to evaluate effects of bread wheat variety and fungicide application on yellow rust epidemics under natural field conditions at Debre Markos University research site, East Gojjam Zone in the main cropping season of 2021/2022 year. Three different fungicides (Tilt (25EC), Natura (250 EW), and Takeoff (293 SC) including fungicide unsprayed combined with five improved wheat varieties (Honkolo, Wane, Liben, Lemu and Kakaba) were used in the experiment and the experiment was laid out in RCBD design with factorial arrangement and replicated three time. Disease data’s (severity, AUDPC, incidence and grain yield were recorded. The maximum disease incidence (100 %), initial and final disease severity (39.75 at 57 DAP and 66.66% at 78 DAP) and AUDPC (1770.71 %-day) recorded from fungicide unsprayed plot on Honkolo variety. But the lowest disease incidence (1.50 %), initial and final severity (1.89 % at 57 DAP and 2.36 % at 78 DAP) and AUDPC (78.93 % - day) were recorded from the combination of Liben variety with Natura (250% EW) fungicide treatment. Moreover, the maximum grain yield (6.00 t/ha) was obtained from combination of Kakaba variety and Natura (250 EW) fungicide treatment plot. While the minimum yield (3.00 t/ha) was recorded from fungicide unsprayed Honkolo variety. Natura (250 EW) fungicide sprayed varieties were effective to against yellow rust and gave the highest values of yield over unsprayed plots and other fungicides application. However, Combination of Kakaba variety and Natura (250 EW) fungicide application was more feasible than other treatments.

Optimizing fungicide application timing for spring dead spot based on soil temperature and season

AbstractSpring dead spot (SDS) (Ophiosphaerella spp.) is the most detrimental disease to warm‐season turfgrasses in areas with cold‐induced dormancy. Fungicide applications do not provide consistent SDS suppression. One reason for this inconsistency is the use of solely calendar‐based fungicide applications instead of considering both calendar date and soil temperature. A field study was conducted at three separate hybrid bermudagrass (Cynodon dactylon (L.) Pers. × transvaalensis Burtt Davy) locations in Virginia to determine the optimal soil temperature and timing for SDS suppression with tebuconazole and isofetamid. Tebuconazole (1.5 kg a.i. ha−1) and isofetamid (4.1 kg a.i. ha−1) were applied at 11 different timings throughout the year based on soil temperatures at a 0‐ to 10‐cm depth. Plots were assessed for SDS severity in the spring and early summer of 2021 and 2022. Two in vitro studies were also conducted with Ophiosphaerella herpotricha and Ophiosphaerella korrae isolates to (1) determine the optimal temperature for growth on potato dextrose agar (PDA) placed on a thermogradient table (13–33°C) and (2) compare the daily growth rate of O. herpotricha and O. korrae isolates at 11, 19, and 27.5°C on PDA. In the field study, isofetamid suppressed SDS more than tebuconazole. Fall applications when soil temperatures were 13°C consistently provided the best SDS suppression. For the in vitro studies, both species grew optimally between 24 and 25°C, yet O. korrae and O. herpotricha growth rates differed at 11°C.

Identification and Application of Streptomyces rapamycinicus CQUSh011 against Potato Late Blight.

Using chemical fungicides is the main strategy for controlling potato late blight (PLB), a devastating pre- and postharvest disease caused by Phytophthora infestans, resulting in environmental pollution and health risks. It is of great importance to develop a biofungicide from microorganisms. Through isolating potato rhizosphere microorganisms, CQUSh011 was found to have antioomycete activity with strong inhibition on vegetative growth and virulence of P. infestans. Morphological and molecular identification indicated that CQUSh011 belongs to Streptomyces rapamycinicus. Based on genome, metabolome, and HPLC quantification, rapamycin and salicylic acid were found to be the two active metabolites against P. infestans. Continuous field trials showed that CQUSh011 has sustainable control efficiency against PLB, and the efficiency was better when combined with Infinito, along with an increased endophytic microbial community and biodiversity in potato roots. The results demonstrated the potential of CQUSh011 as a biofungicide against PLB and provided an alternative strategy for reducing the application of chemical fungicides.

Scab Intensity in Pecan Trees in Relation to Hedge-Pruning Methods.

Pecan is a valuable nut crop cultivated in the southeastern United States. Among the major yield-limiting factors in the region is scab, caused by the plant pathogenic fungus Venturia effusa. Managing scab in tall trees (15 to 25+ m) in pecan orchards is challenging because of the limitations of getting sufficient spray coverage throughout the canopy. We explored the effects of hedge pruning on scab in three orchards: 14-m-tall cv. Desirable trees winter hedge pruned on alternate sides to 11 m (site 1), 18-m-tall cv. Stuart trees hedge pruned on both sides simultaneously to 11 m (site 2), and 15-m-tall cv. Caddo trees winter hedge pruned in winter versus summer to 11 m (site 3). At site 1 and 2, hedge-pruned trees were compared with nonpruned control trees. All trees received recommended fungicide applications to control scab via an air-blast sprayer. Disease incidence and/or severity was assessed at different sample heights on shoots, foliage, and fruit during three seasons (2020, 2021, and 2022). At site 1 the hedge-pruned trees often had significantly or numerically more severe scab on foliage and fruit compared with the control trees, although the differences were mostly small. The frequency of mature fruit with scab severity <10% was greatest on control trees in 2021 and 2022. At site 2, there were few differences between hedge-pruned and control trees (on fruit, scab severity was either significantly less on hedge-pruned trees or not different from the control), but the frequency of mature fruit with scab severity <10% was consistently greatest on hedge-pruned trees. At site 3, scab intensity was low, and there were no significant differences in scab severity between winter- and summer-pruning treatments. At sites 1 and 2, there was generally more severe scab at greater sample heights compared with low in the canopy. At site 3 there was little effect of height on disease. The benefit of hedge pruning likely increases with tree height in scab-susceptible cultivars. If a tree is taller than ∼15 m, a greater proportion of the fruit will be within reach of efficacious spray coverage from air-blast sprayers.

Proteome Profiling of Cucurbita pepo Phyllosphere After Infection by Podosphaera xanthii and Application of Reynoutria sachalinensis Extract

Podosphaera xanthii is the main causal agent of powdery mildew (PM) disease for Cucurbita pepo. Disease control is attained principally by applications of chemical fungicides, along with parallel use of tolerant crop varieties and alternate application of elicitors to control development of disease resistance. To get insight into C. pepo molecular responses to P. xanthii infection and elicitor treatment we studied the proteomic profile differences at the phyllosphere of a zucchini cultivar susceptible to PM, at the onset of P. xanthii (PX) infection and after application of Reynoutria sachalinensis (RS) plant extract, respectively, using a nano-LC-HRMS/MS, Q-Exactive-Orbitrap approach. Analysis of peptide sequences regarding four treatment groups (Control; PX; RS; and RSPX (PX-infected priorly treated with RS)) resulted in 2070 CuGenDB annotations. Three comparisons (treatments vs. Control) encompassed most of the Differentially Expressed Proteins (DEPs). In these three comparisons, KEGG and Gene Ontology functional analyses highlighted unique differentially enriched pathways—some of which included highly expressed proteins—in PX-related (proteasome, pentose phosphate pathway, and carbon fixation), RS-related (biosynthesis of secondary metabolites, flavonoids, and starch and sucrose metabolism), and RSPX-related (pyruvate metabolism and polycomb repressive complex) comparisons, respectively, suggesting distinct mechanisms of early plant responses modulated by PX and RS. Furthermore, in four out of six comparisons the thiamine metabolism pathway was found to be enriched, suggesting a pivotal role in PX-induced responses.

The TOR signalling pathway in fungal phytopathogens: A target for plant disease control.

Plant diseases caused by fungal phytopathogens have led to significant economic losses in agriculture worldwide. The management of fungal diseases is mainly dependent on the application of fungicides, which are not suitable for sustainable agriculture, human health, and environmental safety. Thus, it is necessary to develop novel targets and green strategies to mitigate the losses caused by these pathogens. The target of rapamycin (TOR) complexes and key components of the TOR signalling pathway are evolutionally conserved in pathogens and closely related to the vegetative growth and pathogenicity. As indicated in recent systems, chemical, genetic, and genomic studies on the TOR signalling pathway, phytopathogens with TOR dysfunctions show severe growth defects and nonpathogenicity, which makes the TOR signalling pathway to be developed into an ideal candidate target for controlling plant disease. In this review, we comprehensively discuss the current knowledge on components of the TOR signalling pathway in microorganisms and the diverse roles of various plant TOR in response to plant pathogens. Furthermore, we analyse a range of disease management strategies that rely on the TOR signalling pathway, including genetic modification technologies and chemical controls. In the future, disease control strategies based on the TOR signalling network are expected to become a highly effective weapon for crop protection.

Enhancing of Faba bean (Vicia Faba L.) plant Physiological Tolerance against Rhizoctonia solani damping-off diseases by application of silver nanoparticle and tebuconazole fungicide

The researchers in Egypt have significant difficulty in controlling the development of damping-off disease caused by Rhizoctonia solani in the faba bean plant (Vicia faba L, VF). This is due to the importance of faba beans as a staple food source. Fungicides are used to control either seeds or soil; regrettably, they pollute the ecosystem. As a result, further study is required to identify safe and cost-effective alternatives. In this context, silver nanoparticles were utilized as an inhibitory agent against Rhizoctonia solani and compared to the commercial fungicide Hattric 6% FS (tebuconazole). The minimal inhibitory and fungicidal values for Ag-NPs were 50 and 100 ppm, respectively.Furthermore, Ag-NPs reduced R. solani damping-off intensity. Similarly, Ag-NPs dramatically enhance phenotypic (Shoot length, root length and number of leaves), physiological indicators (soluble sugars, soluble protein and proline), stress markers (Malondialdehyde (MDA), Hydrogen peroxide (H2O2)), protein pattern when compared to infected controls and the chemical fungicide tebuconazole. In conclusion, biosynthesized Ag-NPs are a potentially efficient treatment against R. solani damping-off diseases in Vicia faba, along with a plant growth promoter.

Successful management of Stegasta bosqueella (Lepidoptera Gelechiidae) in peanut with an attract-and-kill strategy.

Rednecked Peanutworm Stegasta bosqueella control is primarily achieved using broad spectrum insecticides targeting the larval stage. However, due to inconspicuous behavior and limited movement of the larvae within the peanut crop, foliar insecticides alone have been insufficient to reduce S. bosqueella populations. The poor effectiveness of chemical products, combined with the necessity of frequent fungicide applications, leads to an overuse of pesticides in peanuts. Given the challenges associated with targeting the larval stage, alternative strategies are needed to improve pest management. Our hypothesis was that by targeting the adult stage, the most mobile stage of the insect, we could decrease the levels of S. bosqueella damage in peanut crops while being less aggressive to the environment. Over 2 years, our study demonstrated that semiochemical-food-based attract and kill treatments significantly reduced the number of S. bosqueella adults captured per food-baited trap per week. This reduction was associated with fewer larvae and decreased plant damage compared to untreated control areas. To optimize this strategy, several key practices must be followed: (a) Prompt treatment application (chemical associated with attractant) should be applied upon detection of an increase in adult trap catches; (b) Timing applications to coincide with peak adult movement (6 pm to 9 pm); and (c) Applying treatments strategically on two peanut rows, 50 m apart, per hectare. The attract-and-kill method can effectively reduce S. bosqueella damage in peanut crops, and has the potential to target other moth species that act as peanut defoliators. © 2024 Society of Chemical Industry.

Sublethal fungicide-insecticide co-exposure affects nest recognition and parental investment in a solitary bee

Fungicides may interact synergistically with insecticides. However, our understanding of the impacts of sublethal insecticide-fungicide combinations on solitary bees is mostly restricted to laboratory studies, providing no information about potential consequences on behavior and reproductive success. We analyzed the effects of a fungicide application, alone and in combination with sublethal levels of an insecticide, on the nesting behavior and reproductive output of the solitary bee Osmia cornuta. We released individually-marked females into oilseed rape field cages, and subsequently sprayed the plants with four treatments: control (water), fungicide (tebuconazole), insecticide (acetamiprid at a sublethal concentration), and mixture (fungicide + insecticide). We recorded nesting activity before and after the sprays and assessed post-spray individual reproductive success. Bees of the single pesticide treatments were unaffected by the sprays and did not differ from control bees in any of the parameters measured. The longevity of bees of the mixture treatment was unaffected. However, these bees showed reduced foraging activity, shorter in-nest pollen-nectar deposition times, and increased difficulty recognizing their nesting cavity, leading to a decrease in provisioning rate, parental investment, and offspring production. Our study demonstrates that co-exposure to a fungicide with otherwise harmless levels of an insecticide caused behavioral effects with consequences on reproductive success. Because longevity was unaffected, these effects would not have been easily detected in a chronic laboratory test. Our results have important implications for bee risk assessment, which should account for exposure to multiple compounds and address behavioral effects and reproductive output under semi-field and/or field conditions.

Labor-saving application of thifluzamide and tricyclazole to seedling trays for integrated control of rice blast and sheath blight

Rice blast (Magnaporthe grisea) and sheath blight (Rhizoctonia solani) are limiting factors for rice production. Co-infection of these pathogens results in a disease complex which is difficult to control. In China, growers are accustomed to applying individual fungicides to manage blast and sheath blight, which require large amounts of labor. Application to seedling trays is a new promising solution for saving labor. In this study, application of combined fungicides with different modes of action to seedling trays to integrate control rice blast and sheath blight was evaluated in vitro assays and field trials. The results showed that the combination of thifluzamide and tricyclazole in the 1:2 ratio had significant synergistic inhibitory effects on the mycelial growth of M. grisea and R. solani, with a synergistic ratio (SR) of 2.17 and 1.49. Results from field trials revealed that thifluzamide + tricyclazole at 1107 and 958.5 g/ha applied to seedling trays was the most effective treatment to reduce the disease index of rice blast with control effects of 83.74–84.96% and 81.34–83.26% in 2022 and 2023, respectively, and no significant differences were observed from tricyclazole at 300 g/ha as foliar sprays twice. Compared to the untreated control, disease index of rice sheath blight was notably reduced by all treatments containing thifluzamide. The highest control was recorded in the treatment of thifluzamide + tricyclazole applied at 1107 g/ha to seedling trays. Moreover, compared to the untreated control, all treatments significantly enhanced rice grain yield by 7.67–17.86% and 3.38–18.91% in 2022 and 2023, respectively. The greatest yield (7429.73 and 7404.73 kg/ha in 2022 and 2023, respectively) was observed from the treatment of thifluzamide + tricyclazole at 1107 g/ha applied to seedling trays, with no significant differences among all the treatments containing tricyclazole. Taken together, these results indicated that seedling tray application of thifluzamide + tricyclazole could be a labor-saving approach to the integrated control of rice blast and sheath blight disease complex, while increasing rice grain yield.