Apple ring rot, one of the most common apple postharvest diseases during storage, is caused by Botryosphaeria dothidea. Presently, the disease management is primarily dependent on chemical fungicide application. Here we demonstrated an endophyte bacterium Bacillus tequilensis QNF2, isolated from Chinese leek (Allium tuberosum) roots considerably suppressed B. dothidea mycelial growth, with the highest suppression of 73.56 % and 99.5 % in the PDA and PDB medium, respectively in vitro confront experiments. In in vivo experiments, B. tequilensis QNF2 exhibited a control efficacy of 88.52 % and 100 % on ring rot disease on postharvest apple fruits inoculated with B. dothidea disc and dipped into B. dothidea culture, respectively. In addition, B. tequilensis QNF2 volatile organic compounds (VOCs) also manifested markedly inhibition against B. dothidea mycelial growth and the ring rot on postharvest apple fruits. Moreover, B. tequilensis QNF2 severely damaged the mycelial morphology of B. dothidea. Finally, B. tequilensis QNF2 significantly repressed the expression of six pathogenicity-related genes, such as adh, aldh, aldh3, galm, pdc1, pdc2, involved in glycolysis/gluconeogenesis of B. dothidea. The findings of the study proved that B. tequilensis QNF2 was a promising alternative for controlling apple ring rot of postharvest apple fruit.

Fusarium graminearum is a destructive fungal pathogen that seriously threatens wheat production and quality. In the management of fungal infections, biological control is an environmentally friendly and sustainable approach. Here, the antagonistic strain ZK-9 with a broad antifungal activity was identified as Bacillus amyloliquefaciens. ZK-9 could produce extracellular enzymes such as pectinase, protease, cellulase, and amylase, as well as plant growth-promoting substances including IAA and siderophore. Lipopeptides extracted from strain ZK-9 had the high inhibitory effects on the mycelia of F. graminearum with the minimum inhibitory concentration (MIC) of 0.8 mg/mL. Investigation on the action mechanism of lipopeptides showed they could change the morphology of mycelia, damage the cell membrane, lower the content of ergosterol and increase the relative conductivity of membrane, cause nucleic acid and proteins leaking out from the cells, and disrupt the cell membrane permeability. Furthermore, metabolomic analysis of F. graminearum revealed the significant differences in the expression of 100 metabolites between the lipopeptides treatment group and the control group, which were associated with various metabolic pathways, mainly including amino acid biosynthesis, pentose, glucuronate and glycerophospholipid metabolism. In addition, strain ZK-9 inhibited Fusarium crown rot (FCR) with a biocontrol efficacy of 82.14 % and increased the plant height and root length by 24.23 % and 93.25 %, respectively. Moreover, the field control efficacy of strain ZK-9 on Fusarium head blight (FHB) was 71.76 %, and the DON content in wheat grains was significantly reduced by 69.9 %. This study puts valuable insights into the antifungal mechanism of lipopeptides against F. graminearum, and provides a promising biocontrol agent for controlling F. graminearum.

To discover novel natural product-based insecticides, a series of (+)-nootkatone-based amine derivatives 3a-t were prepared and evaluated for their insecticidal activities against Mythimna separata Walker, Myzus persicae Sulzer, and Plutella xylostella Linnaeus. Insecticidal assays showed that most of the title (+)-nootkatone derivatives exhibited stronger insecticidal activities against three insect pests than the precursor (+)-nootkatone after the introduction of amine groups on the parent (+)-nootkatone. Compounds 3a, 3d, 3h, 3m, 3n, 3p, and 3r displayed more promising growth inhibitory (GI) effect against M. separata than the commercially available botanical insecticide toosendanin. Compound 3o exhibited the most potent aphicidal activity with an LD50 value of 0.011 μg/larvae, which was 2.09-fold higher than the positive control rotenone. Additionally, compounds 3g and 3n showed more promising larvicidal activity against P. xylostella with LC50 values of 260 and 230 mg/L, respectively, superior to that of rotenone (460 mg/L). Moreover, derivatives 3g and 3n exhibited better control efficacy toward P. xylostella than rotenone under greenhouse conditions. Preliminary mechanistic studies revealed that derivative 3n could inhibit the activity of glutathione S-transferase (GST) in P. xylostella and thus exerted larvicidal activity, and molecular docking further demonstrated that 3n could interact well with some amino acid residues of GST. Finally, the toxicity assay suggested that derivatives 3g and 3n were relatively less toxic to nontarget organisms. These findings will provide insights into the development of (+)-nootkatone derivatives as green pesticides.

Saposhnicovia divaricata (Trucz.) Schischk. is one of the traditional medicinal herbs in northeast China, and its roots are used for medicinal purposes. In 2020, a fungus isolated from S. divaricata seeds was observed to cause root rot of seedlings, leaf spot and stem spot of adult plants in Shuangyashan, Heilongjiang, China. Based on morphological and molecular data, isolates of all fungi were identified as Alternaria alternata. To our knowledge, this is the first report of A. alternata isolated from S. divaricata seeds in China. The carrying rate of S. divaricata seeds from 20 different collection sites reached 100% in 70% of the sites in Hulunbeier area, Inner Mongolia, China. The A. alternata isolate could infect the roots of cucumber, sorghum, mung bean and maize seedlings and cause root rot. Considering the control of seed-associated fungal diseases, prochloraz 45% EW had the best control effect of 92.6%, followed by flusilazole 400 g L-1 EC (88.9%) and azoxystrobin·propiconazole 18.7% SE (70.7%) of 15 fungicides. Further field control efficacy showed that 45% prochloraz EW had an 80% control efficacy on the disease at a dose of 0.225 g L-1. It is recommended that soaking seeds and spraying are the best treatments for controlling seed-associated fungi and leaf spot on S. divaricata caused by A. alternata. Therefore, above methods can effectively prevent the occurrence of fungal diseases of S. divaricata and provide a method to reduce reinfestation in the field.

BACKGROUND: Effective utilization of plant protection UAVs in peanut cultivation management necessitates a comprehensive grasp of how application volume rates and pesticides influence peanut leaf spot and rust control. This study aimed to compare the effects of application volume rates and pesticides on droplet deposition, disease, leaf retention rate and peanut yield. A T20 plant protection unmanned aerial vehicle (UAV) sprayer was used to apply four various pesticide doses. In comparison, a knapsack sprayer was used to spray with an application volume rate of 450 L ha-1.
RESULTS: The results showed a significant difference in droplet deposition between the plant protection UAVs and the electric knapsack sprayer. In the pesticide treatment with an application volume rate of 15.0 L ha-1, there was no significant difference in the deposition on the peanut canopy of each pesticide treatment, but there was a significant difference in the deposition on the ground in the treatment with adding vegetable oil adjuvant. The treatment with added vegetable oil additives showed the worst performance. The treatment with an application volume rate of 22.5 L ha-1 showed the best performance, with the leaf spot control effect being only 0.3% lower than that of the electric knapsack sprayer.
CONCLUSIONS: Plant protection UAV spraying is feasible to control peanut diseases. Considering the operational effectiveness of the plant protection UAV and application volume rate, it is recommended to use an application volume rate of 22.5 L ha-1 without adding vegetable oil adjuvants for field operations. © 2024 Society of Chemical Industry.

Tree peony black spot (TPBS), mainly caused by Alternaria suffruticosae, is a common leaf disease on the ornamental peony, which poses a great threat to the flower buds in the current year and the flowering quality in the next year. However, there is only one fungicide registered for the control of this disease, difenoconazole. In order to avoid the severe problem of pathogen resistance caused by long-term use of difenoconazole, it is necessary to screen more chemical fungicides for the prevention and control of TPBS. In this study, the biological activities of flutolanil, phenamacril, pyraclostrobin, and boscalid on mycelial growth, conidial germination, germ tube elongation, and sporulation quantity of A. suffruticosae were determined, and the field control efficacy was tested to evaluate the preventive and therapeutic activities. Difenoconazole was used as a control simultaneously. The results showed that pyraclostrobin had the strongest inhibitory effects on the conidial germination, mycelium growth, germ tube elongation, and sporulation quantity, with the average EC50 values of 0.0517, 0.5343, 0.0008, and 0.8068 μg/ml, respectively. The inhibitory activity of flutolanil on the four developmental stages of A. suffruticosae was weaker than that of the other three fungicides. Compared with flutolanil, boscalid, the other succinate dehydrogenase inhibitor, had more strong inhibitory effects on the mycelial growth and sporulation quantity, with the average EC50 values of 3.8603 and 1.4760 μg/ml, respectively. Phenamacril had a moderate inhibitory level and had more inhibitory activity on conidial germination and germ tube elongation, with the average EC50 values of 31.5349 and 5.2597 μg/ml, respectively. All of the four fungicides had no significant effects on the shape of spores and germ tubes. The control fungicide difenoconazole had the strongest inhibitory activity on mycelial growth, and the average EC50 value was only 0.3297 μg/ml. However, its inhibitory activity on the other three growth stages was not high. In the field trials, pyraclostrobin had high control efficacy on TPBS even at low concentrations, reaching a minimum of 62.6293%, which was higher than that of difenoconazole. The other three fungicides had higher control efficacy at high concentrations but decreased significantly at low concentrations. Considering the dosage and control efficacy, pyraclostrobin was the first choice for the control of TPBS. Pyraclostrobin is the preferred alternative fungicide to difenoconazole for the prevention and control of TPBS in production.

BACKGROUND: The use of unmanned aerial vehicles (UAVs) for the application of plant protection products (PPPs) in paddy fields is becoming increasingly prevalent worldwide. Despite its growing usage, UAV spraying for rice pest control faces practical challenges, including limited canopy penetration, uneven deposition, and significant spray drift. This study investigated the impact of two tank-mix adjuvants, Wonderful Rosin (Adjuvant-1) and Tiandun (Adjuvant-2), at six volume concentrations, on the spray liquid\'s physicochemical properties, spray drift, plant deposition, and the biological efficacy of rice insecticides using a quadrotor UAV sprayer.
RESULTS: The physicochemical characteristics of the spray liquid influenced spray performance and biological efficacy. Incorporating Adjuvant-1 and Adjuvant-2 led to a decrease in surface tension and contact angle while increasing the viscosity of the spray solution. These alterations in surface tension and viscosity contributed to an optimized droplet size distribution, reduced spray drift, enhanced deposition uniformity and penetration, and improved control efficacy against the rice planthopper in UAV applications. The highest control efficacy was observed at a concentration of 0.5%, showing an improvement of 35.12% (Adjuvant-1) and 20.23% (Adjuvant-2) over applications without tank-mix adjuvant 7 days after treatment.
CONCLUSIONS: The judicious selection of tank-mix adjuvants for UAV PPP applications can significantly enhance spray performance and biological efficacy in controlling rice insects. This study\'s findings offer valuable insights for integrating tank-mix adjuvants into UAV spraying applications. © 2024 Society of Chemical Industry.

One of the phytopathogens that cause severe damage to jalapeño pepper is Leveillula taurica (Lév.) Arnaud, the causative agent of powdery mildew. Synthetic fungicides are currently employed for its control, contributing to adverse effects on human health and the environment. The main objective of this research was to identify the causal agent of powdery mildew and assess the efficacy of chitosan in powdery mildew control on jalapeño pepper. The following treatments were evaluated in laboratory and greenhouse conditions: T1 = 0.0125% chitosan, T2 = 0.0025% chitosan, T3 = 0.05% chitosan, T4 = 0.1% chitosan, T5 = 0.2% chitosan, T6 = tebuconazole 25% (1.8 mL/L water), and T7 = control (water). Symptomatology results indicated that L. taurica is indeed the causative agent of powdery mildew. Treatments T4 and T5 exhibited the lowest percentages of incidences and severity, hence achieving higher control efficacy in the laboratory (57.70 ± 3.85 and 65.39 ± 3.85) and greenhouse (56.67 ± 4.08 and 70 ± 8.16%) compared to T6 (control efficacy, 38.46 ± 0.00% in the laboratory and 50 ± 0.00% in the greenhouse). The chitosan derived from shrimp had a significant impact on the cell walls of L. taurica spores and mycelium. Consequently, chitosan emerges as a viable organic alternative to fungicides for controlling powdery mildew in jalapeño pepper.

Chemical fertilizer and pesticide are necessary in agriculture, which have been frequently used, sometimes even at the same time or in combination. To understand the interactions of them could be of significance for better use of these agrochemicals. In this study, the influence of chemical fertilizers (urea, potassium sulfate, ammonium sulfate and superphosphate) on the control efficacy and environmental behavior of abamectin was investigated, which could be applied in soil for controlling nematodes. In laboratory assays, ammonium sulfate at 1 and 2 g/L decreased the LC50 values of abamectin to Meloidogyne incognita from 0.17 mg/L to 0.081 and 0.043 mg/L, indicating it could increase the contact toxicity. In greenhouse trial, ammonium sulfate at 1000 mg/kg increased the control efficacy of abamectin by 1.37 times. Meanwhile, the combination of abamectin with ammonium sulfate could also promote the tomato seedling growth as well as the defense-related enzyme activity under M. incognita stress. The persistence and mobility of abamectin in soil were significantly elevated by ammonium sulfate, which could prolong and promote the control efficacy against nematodes. These results could provide reference for reasonable use of abamectin and fertilizers so as to increase the control efficacy and minimize the environmental risks.

BACKGROUND: Ralstonia solanacearum, a notorious and refractory bacterial plant pathogen, threatens multiple vegetable crops and causes significant economic loss in agriculture. Long-term use of traditional medicines not only increases the problem of drug resistance, but also causes great environmental pollution. Therefore, there is an urgent need to develop new agents with high efficacy and low toxicity.
RESULTS: In this study, we have synthesized and characterized graphitic carbon nitride incorporated copper oxide composite (g-C3N4@CuO), which showed higher antimicrobial effect than graphitic carbon nitride nanosheets (g-C3N4 nanosheets) and copper oxide nanoparticles (CuONPs). Ralstonia solanacearum exposed to g-C3N4@CuO exhibited higher levels of oxygen toxicity, cell membrane damage, DNA damage, motility disruption and even cell death compared to g-C3N4 nanosheets and CuONPs. In addition, g-C3N4@CuO was more effective in the control of tobacco bacterial wilt than g-C3N4 nanosheets and CuONPs.
CONCLUSIONS: Thus, this study provides a new perspective on g-C3N4@CuO control of bacterial diseases in crops, and the mechanism is related to the destruction of cell membrane damage and motility disruption. © 2024 Society of Chemical Industry.