Response of soil phosphatase activity and soil phosphorus fractions to the application of chloropicrin and azoxystrobin in ginger cultivation.

BACKGROUND: Soil fumigation can change soil nutrient cycling processes by affecting soil beneficial microorganisms, which is a key issue for soil fertility. However, the effect of combined application of fumigant and fungicide on soil phosphorus (P) availability remains largely unclear. We investigated the effects of the fumigant chloropicrin (CP) and the fungicide azoxystrobin (AZO) on soil phosphatase activity and soil P fractions in ginger production using a 28-week pot experiment with six treatments: control (CK), a single application of AZO (AZO1), double applications of AZO (AZO2), CP-fumigated soil without AZO (CP), CP combined with AZO1 (CP + AZO1) and CP combined with AZO2 (CP + AZO2). RESULTS: AZO application alone significantly increased the soil labile P fractions (Resin-P + NaHCO3 -Pi + NaOH-Pi) at 9 weeks after planting (WAP) but decreased the soil phosphatase activity at 28 WAP. CP fumigation significantly reduced the soil phosphatase activity but increased the proportions of soil labile P fractions (Resin-P + NaHCO3 -Pi + NaHCO3 -Po) to total P (TP) by 9.0-15.5% throughout the experiment. The combined application of CP and AZO had a synergistic effect on soil phosphatase activity and soil P fractions compared with a single application. CONCLUSION: Although AZO application and CP fumigation can increase soil available P in the short term, they might negatively affect soil fertility in the long run by inhibiting soil phosphatase activity. Soil microbial activities, especially microorganisms related to P cycling, may be responsible for the variations in soil P availability, but further research is needed. © 2023 Society of Chemical Industry.

Effects of chloropicrin fumigation and azoxystrobin application on ginger growth and phosphorus uptake.

Soil chloropicrin (CP) fumigation helps to increase crop yields by eliminating soil-borne diseases which inhibit plant growth. However, little is known about the effect of the CP fumigation combined with fungicide application on plant growth and nutrient uptake. In this study, we conducted a mesocosm experiment with six treatments: CK (untreated soil), AZO1 (a single application of azoxystrobin (AZO)), AZO2 (double applications of AZO), CP (CP fumigation with no AZO), CP+AZO1 (CP combined with AZO1) and CP+AZO2 (CP combined with AZO2) to investigate the effects of CP fumigation and AZO application on ginger growth and phosphorus (P) uptake. Results showed that a single application of AZO had no significant effect on ginger height, biomass and P uptake whether treated with or without CP fumigation, whereas double applications of AZO combined with CP fumigation significantly improved ginger height and the total amount of P in root (P < 0.05). Meanwhile, AZO residues were similar in all treatments with the same number of applications, with less than 50% remaining in the soil after 7 days applied, indicating that CP fumigation treatment did not influence AZO degradation in ginger cultivation. In addition, although the differences in P use efficiency observed across the different treatments were not significant, they nevertheless suggest that the P budget and soil microbial activity may contribute to those differences. Therefore, further studies should be done to link P cycling with microbial communities, and how these related to fumigation and fungicide application.

Fungicide and insecticide exposure adversely impacts bumblebees and pollination services under semi-field conditions.

Sulfoximines, the next generation systemic insecticides developed to replace neonicotinoids, have been shown to negatively impact pollinator development and reproduction. However, field-realistic studies on sulfoximines are few and consequences on pollination services unexplored. Moreover, the impacts of other agrochemicals such as fungicides, and their combined effects with insecticides remain poorly investigated. Here, we show in a full factorial semi-field experiment that spray applications of both the product Closer containing the insecticide sulfoxaflor and the product Amistar containing the fungicide azoxystrobin, negatively affected the individual foraging performance of bumblebees (Bombus terrestris). Insecticide exposure further reduced colony growth and size whereas fungicide exposure decreased pollen deposition. We found indications for resource limitation that might have exacerbated pesticide effects on bumblebee colonies. Our work demonstrates that field-realistic exposure to sulfoxaflor can adversely impact bumblebees and that applications before bloom may be insufficient as a mitigation measure to prevent its negative impacts on pollinators. Moreover, fungicide use during bloom could reduce bumblebee foraging performance and pollination services.

Treating honey bees with an extremely low frequency electromagnetic field and pesticides: Impact on the rate of disappearance of azoxystrobin and λ-cyhalothrin and the structure of some functional groups of the probabilistic molecules.

The purpose of these laboratory tests was to assess the impact of 50 Hz EMF (electromagnetic field) on the disappearance of azoxystrobin (active ingredient (AI) of Amistar 250 SC) and λ-cyhalothrin (AI of Karate Zeon 050 CS) in the body of honey bees (Apis mellifera) and the structure of some functional groups of the probabilistic molecules in their organisms. Amistar 250 SC (an azoxystrobin-based fungicide; ABF) and Karate Zeon 050 CS (a λ-cyhalothrin-based insecticide; CBI) are plant protection products (PPPs) applied to bee-pollinated-crops. Chromatographic methods were used to assess the rate of AI disappearance. EMF affected the rate of disappearance of azoxystrobin and λ-cyhalothrin in bees within 6 h of intoxication. When these substances were used separately their disappearance in the presence of EMF slowed from 12.6% to 10.5% h-1 and from 9.2% to 4.8% h-1, respectively, and accelerated when used in a mixture, from 14.1% to 14.7% h-1 and from 9.3% to 11.5% h-1 respectively. Fourier Transform Infrared (FTIR) spectroscopy was used to analyze changes in the functional groups of the probabilistic molecules of the tested bees. To obtain the information about the spectra variations we used the Principal Component Analysis. It has been shown, that EMF statistically significantly interferes with amide I and II, symmetric PO32- group from DNA, RNA and phospholipids vibrations. It also increased the number of changes of functional groups of the probabilistic molecules caused by ABF, but at the same time limited the changes in the functional groups studied in bees treated with CBI and a mixture containing both of them. In addition, exposure to EMF in bees treated with fungicide or insecticide, separately, and with both preparations caused differences (p < 0.05) in the secondary structure of proteins compared to controls. The obtained results indicate that EMF may affect the rate of metabolism and the detoxification process of pesticides in bees, depending on the AI of PPPs, applied individually or together. However, further detailed research is required to explain the mechanism of EMF as a detoxification modulator.

Simultaneous determination and risk assessment of metalaxyl and azoxystrobin in potato by liquid chromatography with tandem mass spectrometry.

A liquid chromatography with tandem mass spectrometry method was developed and validated to simultaneously determine metalaxyl and azoxystrobin in soil, potato, and potato foliage samples. The samples were extracted by 20 mL of acetonitrile and purified with dispersive solid-phase extraction using octadecyl silane as sorbent. The method showed good linearity (determination coefficients ≥ 0.9926) for metalaxyl (2.5-500 ng/mL) and azoxystrobin (5-1000 ng/mL). The limits of detection and quantification for both fungicides were 1.5-20 µg/kg. The average recoveries in soil, potato, and potato foliage were 83.07-92.87% for metalaxyl and 82.71-98.53% for azoxystrobin. The intra- and inter-day relative standard deviations were all less than 9%. The method was successfully applied on the residual analysis of metalaxyl and azoxystrobin in field trial samples. The results showed that the concentrations of metalaxyl and azoxystrobin in potato samples collected from Guizhou and Hunan were below 50 and 100 µg/kg (maximum residue limit set by China), respectively, at 5 days after the last application. When following the recommended application manual, metalaxyl and azoxystrobin do not present health concerns to the population because the risk quotients are far below 100%. All the above data could help and promote the safe and proper use of metalaxyl and azoxystrobin in potato.

Dynamic residual pattern of azoxystrobin in Swiss chard with contribution to safety evaluation.

This study aimed at quantifying the residual amount of azoxystrobin in Swiss chard samples grown under greenhouse conditions at two different locations (Gwangju and Naju, Republic of Korea). Samples were extracted with acetonitrile, separated by salting out, and subjected to purification by using solid-phase extraction. The analyte was identified using liquid chromatography-ultraviolet detection. The linearity of the calibration range was excellent with coefficient of determination 1.00. Recovery at three different spiking levels (0.1, 0.5, and 4 mg/kg) ranged between 82.89 and 109.46% with relative standard deviation <3. The limit of quantification, 0.01 mg/kg, was considerably much lower than the maximum residue limit (50 mg/kg) set by the Korean Ministry of Food and Drug Safety. The developed methodology was successfully used for field-treated leaves, which were collected randomly at 0-14 days following azoxystrobin application. The rate of disappearance in/on Swiss chard was ascribed to first-order kinetics with a half-life of 8 and 5 days, in leaves grown in Gwangju and Naju greenhouses, respectively. Risk assessments revealed that the acceptable daily intake percentage is substantially below the risk level of consumption at day 0 (in both areas), thus encouraging its safe consumption.

Two new fatty acids esters were detected in ginseng stems by the application of azoxystrobin and the increasing of antioxidant enzyme activity and ginsenosides content.

Panax ginseng C.A. Meyer is a valuable herb in China that has also gained popularity in the West because of its pharmacological properties. The constituents isolated and characterized in ginseng stems include ginsenosides, fatty acids, amino acids, volatile oils, and polysaccharides. In this study, the effects of fungicide azoxystrobin applied on antioxidant enzyme activity and ginsenosides content in ginseng stems was studied by using Panax ginseng C. A. Mey. cv. (the cultivar of Ermaya) under natural environmental conditions. The azoxystrobin formulation (25% SC) was sprayed three times on ginseng plants at different doses (150ga.i./ha and 225ga.i./ha), respectively. Two new fatty acids esters (ethyl linoleate and methyl linolenate) were firstly detected in ginseng stems by the application of azoxystrobin as foliar spray. The results indicated that activities of enzymatic antioxidants, the content of ginsenosides and two new fatty acids esters in ginseng stems in azoxystrobin-treated plants were increased. Azoxystrobin treatments to ginseng plants at all growth stages suggest that the azoxystrobin-induced delay of senescence is due to an enhanced antioxidant enzyme activity protecting the plants from harmful active oxygen species (AOS). The activity of superoxide dismutase (SOD) in azoxystrobin-treated plants was about 1-3 times higher than that in untreated plants. And the effects was more significant (P=0.05) when azoxystrobin was applied at dose of 225ga.i./ha. This work suggests that azoxystrobin plays an important role in delaying of senescence by changing physiological and biochemical indicators and increasing ginsenosides content in ginseng stems.

Dissipation rates and residues of fungicide azoxystrobin in ginseng and soil at two different cultivated regions in China.

The maximum residue limit (MRL) for fungicide azoxystrobin in ginseng has not yet been established in China. This is partially due to the lack of its dissipation and residue data at China's main ginseng production areas. In this work, the dissipation rates and residue levels of azoxystrobin in ginseng roots, plant parts (stems and leaves), and soil in Beijing and Jilin Province, China were determined using gas chromatograph-mass spectrometry (GC-MS). The mean half-life of azoxystrobin in ginseng plant parts was 1.6 days with a dissipation rate of 90 % over 21 days. The mean half-life in soil was 2.8 days with a dissipation rate of 90 % over 30 days. Dissipation rates from two geographically separated experimental fields differed, suggesting that these were affected by local soil characteristics and climate. Maximum final residues of azoxystrobin in ginseng roots, plant parts, and soil were determined to be 0.343, 9.40, and 0.726 mg kg(-1), respectively. Our results, particularly the high residues of azoxystrobin observed in ginseng plant parts, provide a quantitative basis for revising the application of this pesticide to ginseng.