Soil Solarization Research Articles

Effects of High Tunnel Soil Solarization on Sclerotinia sclerotiorum in the Temperate Climate of Central Kentucky.

Diseases caused by Sclerotinia spp. can affect a wide range of plants, including vegetables, with yield losses ranging from 10 to 50%. Sclerotinia diseases can be especially problematic in high tunnels where high-value vegetable crops are planted in early spring to extend the growing season, achieve earlier harvest, and bring higher profits. Fungicide applications and crop rotations are limited due to product application restrictions and constraints on time, crop resistance, and profitability. Soil solarization is a cultural management method that uses transparent polyethylene to raise soil temperatures via solar irradiation to kill pathogens, pests, and weeds. A two-year study was conducted in a Kentucky high tunnel to determine the maximum temperature potential of solarization at various soil depths at different durations during different seasons and to identify temperatures at which S. sclerotiorum sclerotia lose viability. The experiment included solarization treatments of 2, 4, and 6 weeks and a non-solarized control implemented in spring, summer, and fall. Sclerotia and temperature data loggers were buried at 5.1, 10.2, and 15.2 cm soil depths. The number of hours at which soil temperatures reached ≥ 40 °C was greatest in summer in both years, followed by fall, and then spring. The highest average daily maximum soil temperature reached was 48.9°C, which occurred during the summer 6-week solarization in Year 1. The viability of buried sclerotia was overall lower in solarized treatments compared to non-solarized treatments in both years. In general, the 2-week solarization treatment had significantly higher percent sclerotial germination than the 4-week and 6-week treatments, which were not significantly different from one another. The viability of sclerotia was progressively higher with burial depth. In both years, sclerotia germination was significantly lower in summer compared to spring and fall.

Advances and Challenges in Pest Management for Protected Cultivation in India: Integrative Approaches and Future Prospects

Poly house farming in India has transformed agriculture by enabling year-round crop production and protecting crops from adverse weather. However, the controlled environment of poly houses represents unique challenges in pest management, making it crucial to implement effective strategies to maintain crop health and yield. Integrated Pest Management (IPM) offers a comprehensive approach that combines cultural, biological and chemical practices to control pests while minimizing environmental impact. The advantages of protected cultivation include increased productivity, improved produce quality and efficient resource utilization. Despite these benefits, poly house farming faces limitations such as high initial costs, the need for meticulous planning and ongoing crop protection requirements. Pest identification is vital for effective management, as misidentification can lead to inappropriate control measures. Common pests in poly houses include insects, slugs, mites, nematodes, pathogens and weeds. Pest monitoring strategies such as scouting, using monitoring tools and record-keeping are essential for timely and effective management interventions. Management strategies encompass physical, biological and chemical methods. Physical approaches include the use of sticky and pheromone traps, while biological control involves the release of natural predators and entomopathogens. Chemical management involves both biorational pesticides and conventional chemicals, with IPM emphasizing the integration of these methods to reduce reliance on harmful chemicals. Preventive measures like insect-proof screens and soil solarization, along with curative measures and advanced technologies like video camera networks and decision support systems, are pivotal for effective pest control. Future prospects include improving technology standards, enhancing computerized control systems, and fostering research and government support to advance protected cultivation in India.

Integrated Farming System: A Sustainable Approach towards Modern Agriculture

Integrated farming system (IFS) is an integrated approach towards sustainable agriculture in this modern era. It is the integration of various agricultural enterprises or practices such as crops, livestock, Poultry, fish, agroforestry, horticulture, vermicomposting, Mushroom cultivation and beekeeping, in a single farming system. IFS is considered as the efficient tool for enhancing the profitability of farming systems especially for small and marginal farmers. The purposes or objectives of the IFS are: It enhances the productivity per unit area; Agriculture waste management; Soil health management and soil conservation; Generation of diversified income round the year; less use of chemicals; Increasing the yield of all integrated components and food security. IFS include various components or enterprises. These enterprises not only increase the farmer’s income but also increase employment generation of a family. The juadicious integration of these agricultural enterprises improves the socio-economic status of the farmers. The crop production component of IFS includes the cultivation of various economically important crops such as cereals, pulses, vegetables, fruits, and herbs. To maintain the soil health & fertility and management of Plant diseases and pests, various cultural methods such as intercropping, crop rotation, soil solarisation, organic amendment, Mulching, etc. Mushroom cultivation is also one of the important enterprises in IFS that contribute towards increase in farmer’s income. Another important component of IFS includes the rearing of different types of livsestock such as cows, goats, sheep, Duckery, Piggery, Apiary, and poultry. Livestock provides a source of income and produces manure, which can be used as fertilizer for crops. Biogas is another enterprise which is the use of agricultural and animal waste to produce energy. This Bioenergy helps to reduce the dependence on fossil fuels and provide a source of income for farmers. There are various models that can be used in IFS like Horticulture+ Piggery+ Fisheries+ Plantation crops and Agriculture+ Horticulture+ Poultry+ Fishery+ Mushroom. Hence, Integrated Farming System is a promising approach for increasing productivity, increasing farmer’s income by utilizing the agricultural and animal waste, recycling farm by-products and efficient utilization of available resources.

Identification of hub genes and potential networks by centrality network analysis of PCR amplified Fusarium oxysporum f. sp. lycopersici EF1α gene

BackgroundFusarium wilt is a devastating soil-borne fungal disease of tomato across the world. Conventional method of disease prevention including usage of common pesticides and methods like soil solarisation are usually ineffective in the treatment of this disease. Therefore, there is an urgent need to identify virulence related genes in the pathogen which can be targeted for fungicide development.ResultsPathogenicity testing and phylogenetic classification of the pathogen used in this study confirmed it as Fusarium oxysporum f. sp. lycopersici (Fol) strain. A recent discovery indicates that EF1α, a protein with conserved structural similarity across several fungal genera, has a role in the pathogenicity of Magnaporthe oryzae, the rice blast fungus. Therefore, in this study we have done structural and functional classification of EF1α to understand its role in pathogenicity of Fol. The protein model of Fol EF1α was created using the template crystal structure of the yeast elongation factor complex EEF1A:EEF1BA which showed maximum similarity with the target protein. Using the STRING online database, the interactive information among the hub genes of EF1α was identified and the protein–protein interaction network was recognized using the Cytoscape software. On combining the results of functional analysis, MCODE, CytoNCA and CytoHubba 4 hub genes including Fol EF1α were selected for further investigation. The three interactors of Fol EF1α showed maximum similarity with homologous proteins found in Neurospora crassa complexed with the known fungicide, cycloheximide. Through the sequence similarity and PDB database analysis, homologs of Fol EF1α were found: EEF1A:EEF1BA in complex with GDPNP in yeast and EF1α in complex with GDP in Sulfolobus solfataricus. The STITCH database analysis suggested that EF1α and its other interacting partners interact with guanosine diphosphate (GDPNP) and guanosine triphosphate (GTP).ConclusionsOur study offers a framework for recognition of several hub genes network in Fusarium wilt that can be used as novel targets for fungicide development. The involvement of EF1α in nucleocytoplasmic transport pathway suggests that it plays role in GTP binding and thus apart from its use as a biomarker, it may be further exploited as an effective target for fungicide development. Since, the three other proteins that were found to be tightly associated Fol EF1α have shown maximum similarity with homologous proteins of Neurospora crassa that form complex with fungicide- Cycloheximide. Therefore, we suggest that cycloheximide can also be used against Fusarium wilt disease in tomato. The active site cavity of Fol EF1α can also be determined for computational screening of fungicides using the homologous proteins observed in yeast and Sulfolobus solfataricus. On this basis, we also suggest that the other closely associated genes that have been identified through STITCH analysis, they can also be targeted for fungicide development.

Enhanced activity of Trichoderma asperellum introduced in solarized soil and its implications on the integrated control of strawberry-black root rot

An effective method for maintaining the activity and longevity of microorganisms in adverse conditions is microencapsulation. In the present study, synthetic alginate pellets were developed as carriers for the biocontrol agent Trichoderma asperellum. In two field experiments, solarization was applied for three weeks to loamy clay soil that was naturally infested with strawberry-black root rot fungi (Fusarium solani, Rhizoctonia solani and Machrophomina phaseolina). Following solarization, T. asperellum-based alginate pellets or spore suspension were added to the soil. Data reveal that, three weeks solarization of irrigated soil increased its maximum temperature reached by 11–14.2 °C (1–10 cm depth), 11.6–13.1 °C (11–20 cm depth) and 10.1–12.2 °C (21–30 cm depth). In either trial, solarization also successfully lowers the vitality of strawberry-black root rot fungi directly after the solarization phase. When compared to controls, strawberry-black root rot was substantially less common in solarized plots. In two field trials, soil solarization followed by inoculation with alginate pellets based on T. asperellum led to the greatest reductions in black root rot incidence (59.3 and 74.1 %) and severity (72.5 and 75.2 %), as compared to un-solarized control plots. In vivo studies, this treatment dramatically increased the activity of defensive enzymes (peroxidase and chitinase) and strawberry yield (60.5 and 60.0 %, respectively), as compared to non-solarized control plots. In two field studies, the rhizosphere population of native Trichoderma spp. Developed more in solarized soils after the application of alginate pellets based on T. asperellum (86.5 and 83.6 %, respectively), compared to the non-solarized control.

Soil Solarization Efficiently Reduces Fungal Soilborne Pathogen Populations, Promotes Lettuce Plant Growth, and Affects the Soil Bacterial Community.

Lettuce is the most cultivated leafy vegetable in Greece; however, due to the adopted intensive cropping system, its cultivation is susceptible to many soilborne pathogens that cause significant yield and quality losses. In the current study, the impact of various soil disinfestation methods such as solarization, chemical disinfestation, and application of a biofungicide were evaluated in a commercial field that has been repeatedly used for lettuce cultivation. The populations of soilborne pathogens Rhizoctonia solani, Pythium ultimum, Fusarium oxysporum, and Fusarium equiseti were measured via qPCR before and after the implementation of the specific disinfestation methods. Although all the tested methods significantly reduced the population of the four soilborne pathogens, soil solarization was the most effective one. In addition, solarization reduced the number of lettuce plants affected by the pathogens R. solani and F. equiseti, and at the same time, significantly influenced the growth of lettuce plants. Amplicon sequence analysis of 16S rRNA-encoding genes used to study the soil bacterial community structure showed that Firmicutes, Proteobacteria, and Actinobacteria were the predominant bacterial phyla in soil samples. In general, solarization had positive effects on Firmicutes and negative effects on Proteobacteria and Actinobacteria; soil fumigation with dazomet increased the relative abundance of Firmicutes and Proteobacteria and reduced the corresponding values of Actinobacteria; and biofungicide had no significant effects on the three predominant bacterial phyla. The bacterial community composition and structure varied after the application of the soil disinfestation treatments since they imposed changes in the α- and β-diversity levels. The results of this study are expected to contribute towards implementing the most effective control method against the most common soilborne pathogens in intensively cultivated fields, such as those cultivated with leafy vegetables.

Soil solarisation delivers near zero levels of Fusarium pseudograminearum in cereal crown rot reference sites

The development of commercial varieties that are resistant or tolerant to crown rot caused by Fusarium species is an important goal for cereal breeding programs internationally. Ideally, this research requires experimental sites that are initially free from Fusarium in order to establish treatment plots that compare growth in the presence and absence of these soil- and stubble-borne pathogens. Specifically, the assessment of tolerance requires control plots free of disease to determine the reduction in crop yield in plots where the disease is present. The ability of soil solarisation to reduce the background Fusarium pseudograminearum level occurring at experimental sites in comparison to current stubble management techniques was investigated across three field trials at Wellcamp in Queensland. Stubble from a susceptible durum (Triticum turgidum ssp. durum) cultivar inoculated with F. pseudograminearum was incorporated by cultivation into the trial sites to establish a significant background level of inoculum prior to the application of all subsequent treatment plots. In these trials, solarisation over a period of twelve weeks reduced the presence of F. pseudograminearum to low detection levels when compared to the traditional crown rot management techniques of cultivation or growth of the non-host cover crops mungbean (Vigna radiata) and soybean (Glycine max). No negative effects of solarisation were observed on a subsequent crop of bread wheat (Triticum aestivum), with significantly higher yields observed in the solarised treatments. Solarisation has the potential to deliver near zero level crown rot reference sites for experimental purposes in one short application between cropping seasons.

Enhancing the effects of solarization-based approaches to suppress Verticillium dahliae inocula affecting tomato in greenhouse

The main concerns regarding the management of soilborne pathogens of vegetable crops through fumigants are due to their detrimental effects on the human health and environment. Due to global restrictions, soil solarization alone or combined with low-impact measures are being re-evaluated as eco-friendly alternatives to replacement of phasing-out or banned fumigants. Three experiments were performed to compare the performance of traditional and innovative films in increasing thermal performance under different partially opened or kept closed greenhouses. The effects of treatment alone or combined with Brassica pellet (Biofence®) incorporation were tested in suppressing microsclerotia of Verticillium dahliae, causing wilt of tomato and vegetable crops. Although inducing different thermal regimes at depths 15 and 30-cm depths, all films were effective in reducing microsclerotia in soil compared to the bare plots under different greenhouse conditions. The performances achieved in closed greenhouse were better than those achieved in greenhouses with the side openings kept open. In these latter conditions, green-colored ethylene-vinyl-acetate (EVA) and uncolored EVA film well performed when combined with Brassica pellet, achieving better results than those obtained in the plots mulched with film or amended alone, respectively. Smoky gray low-density polyethylene (LDPE), followed by uncolored EVA and polyamide virtually impermeable film (PA-VIF) were the most effective in reducing/suppressing V. dahliae microsclerotia within 3-to-8 weeks of treatment in closed greenhouse whereas green EVA showed lesser performance. PA-VIF and EVA green film are attractive since they may be used in combination with biofumigants or left on as mulching for weed control of crops. This paper indicates that sustainable solarization-based approaches with different films alone or integrated with Brassica incorporation can also be successfully pursued against thermo-tolerant pathogens as V. dahliae. Moreover, our findings preliminarily show that the choice of film and treatment duration should be modulated based on the greenhouse operative conditions.

Integrated Management of Rhizome Rot and Wilt Disease Complex of Ginger (Zingiber officinale) – A Review

This review article focuses on integrated management options for ginger diseases, especially rhizome rot and wilt. We compiled the results of several strategies, including chemical treatments, cultural practices, soil solarization, organic additions, and biological management for rhizome rot and wilt disease complex of ginger. Effective approaches includes (i) raise the temperature by soil solarization, (ii) additions of soil amendments like wood sawdust, oil cakes, neem cakes that prevent soil pathogen and simultaneously improve soil health, (iii) cultural techniques such as soil selection, crop rotation and intercropping, (iv) biological control using Trichoderma species is another useful method to lower infestation and increase ginger yield, and (v) use of chemical control measures such as Ridomil MZ, Metalaxyl, and Streptomycin. The above-listed aspects can be integrated to develop integrated management strategies that aid in developing a treatment strategy for management for rhizome rot and wilt disease complex of ginger.

Rapid Detection of a Downy Mildew Pathogen, Peronospora destructor, in Infected Onion Tissues and Soils by Loop-Mediated Isothermal Amplification.

Downy mildew of onion caused by a soil-inhabiting water mold, Peronospora destructor, is one of the most devastating diseases that can destroy entire onion fields in a matter of days. In this study, we developed a loop-mediated isothermal amplification (LAMP) assay that allows for rapid detection of P. destructor by visual inspection. The internal transcribed spacer 2 region of P. destructor was used to design primer sets for LAMP reactions. The optimal temperature and incubation time were determined for the most efficient primer set. In the optimized condition, the LAMP assay exhibited at least 100 times more sensitivity than conventional PCR, detecting femtogram levels of P. destructor genomic DNA (gDNA). Detection of the pathogen from a small number of spores without gDNA extraction further confirmed the high sensitivity of the assay. For specificity, the LAMP assay was negative for gDNA of other fungal pathogens that cause various diseases on onion and oomycetes, whereas the assay was positive for gDNA extracted from onion tissues showing the typical downy mildew symptoms. Finally, we examined the efficacy of the LAMP assay in detection of P. destructor in soils. Soils collected from onion fields that had been contaminated with P. destructor were solarized for 60 days. Whereas the LAMP assay was negative for the solarized soils, we were able to detect P. destructor that oversummers in fields. The LAMP assay developed in this study enables rapid detection and diagnosis of downy mildew of onion in infected tissues and in soil.

Synergistic strategies for sustainable crop protection: harnessing soil solarization and biofumigants to combat damping-off pathogens in Solanaceous vegetable crops

Synergistic strategies for sustainable crop protection: harnessing soil solarization and biofumigants to combat damping-off pathogens in Solanaceous vegetable crops

Characterization of Bacillus velezensis DCJ 2 isolated from the rhizosphere soil of aglaonema ‘Maria’ and investigation of its plant growth-promoting effects

Aglaonema ‘Maria’ is one of the key foliage plants that has gained high demand in foreign destinations in the last few years. This study was conducted to characterize Bacillus velezensis DCJ 2, assess its plant growth promotion effect and investigate the effectiveness of different delivery methods of the bacterial inoculum for the growth promotion of Aglaonema ‘Maria’. In this context, DCJ 2, isolated from the rhizosphere soil of A. Maria was screened to investigate its potential as a plant growth-promoting bacterium. The pure culture of DCJ 2 maintained on nutrient agar was utilized for morphological, biochemical and physiological examinations. The molecular characterization of the strain was performed with different primer pairs targeting 16SrRNA, gyrA, pgsB and sugar kinase genes of DCJ 2. A pot experiment was carried out to investigate the plant growth promotion effect. It was conducted in the greenhouse as per the complete randomized block design with eight treatments and five replicates. . Healthy plants of A. ‘Maria’ established in field soil and solarized soil were treated with 100 ml of the suspension of the DCJ 2 at the rate of 10 8 CFU/ml either as a soil drench or foliar spray. The partial 16SrRNA, gyrA, pgsB and sugar kinase gene sequences of DCJ 2, BLAST searched in the NCBI database revealed that it has a high similarity to Bacillus velezensis. The pot experiment showed that the application of strain DCJ 2 as a soil drench to solarized soil (Treatment 6) yielded a significant increase in growth parameters at p=0.05. Based on molecular analysis, morphological, biochemical, and physiological reactions, DCJ 2 was identified as Bacillus velezensis. This study revealed that B. velezensis DCJ 2 has the potential to boost the growth of A. Maria and hence serve as a base for developing a biofertilizer.

Effect of Various Weed Management Options on Weed Dry Matter, Yield Attributes and Yield of Sweet Corn (Zea mays L. saccharata) under Organic Production System

A field experiment was conducted at Instructional cum Research Farm, Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.) during kharif 2019 entitled “Effect of various weed management options on weed dry matter, yield attributes and yield of sweet corn (Zea mays L. saccharata) under organic production system”. The soil of the experimental site was clayey in texture, neutral in reaction and low in nitrogen, medium in phosphorus and high in potassium. The experiment was laid out in Randomized Block Design with three replications. The weed flora of the experimental site was dominated by Echinocloa colona, Alternanthera sessilis, Parthenium hysterophorus, Cyperus iria. Results revealed that the highest green cob yield of sweet corn was recorded in stale seed bed + reduced spacing (upto 25%) + mulching with paddy straw + 20 DAS hand weeding (7.63t ha-1 ) which was 83.48% higher than the weedy check. The green cob yield in stale seed bed + reduced spacing (upto 25%) + mulching with paddy straw + 20 DAS hand weeding was found to be at par with mulching with waste polythene bags (ITK-practices) (7.45t ha- ), hand weeding twice carried out at 20 and 40 DAS (7.33 t ha-1) and soil solarization with 25µ polythene mulch during summer + one hand weeding at 20 DAS(6.94t ha-1). Although grain yield in other weed management practices was significantly lower than stale seed bed + reduced spacing (upto 25%) + mulching with paddy straw + 20 DAS hand weeding treatments but higher than weedy check. Similarly, As regards total weed dry weight at harvest, the total lowest weed dry weight was observed in stale seed bed + reduced spacing (upto 25%) + mulching with paddy straw + hand weeding at 20 DAS(3.45gm-2) followed by mulching with waste polythene bags (ITK- practices)(4.71 gm-2), hand weeding at 20 and 40 DAS (4.96gm-2)and soil solarization with 25µ polythene mulch during summer + one hand weeding at 20 DAS(5.08 gm-2). However, higher WCE was noticed in these treatment over weedy check. The weedy check was significantly inferior in all the yield attributes and green cob yield of sweet corn.

Sunlight can have a stronger influence than air temperature on soil solarisation: observational evidence from Australia

Soil solarisation is a method for pest and weed control pioneered in agriculture, and it is increasingly being adopted by restoration practitioners. Solarisation works by covering moist soil during hot periods with a sheet of clear plastic. The success of soil solarisation depends in large part on increasing the temperature of the topsoil. Topsoil temperature depends on several physical variables, including soil moisture content, ambient temperature, and sunlight intensity. In restoration scenarios, solarisation can be used to reduce weed and pathogen loads prior to planting target plants. It is rarely possible to have tight control over all the variables that are important for solarisation; however, practitioners can time interventions to maximise seasonal temperature and sunlight intensity. In this study, we investigated how these two key physical variables – temperature and sunlight – contributed to the success of soil solarisation. We found that while both ambient temperature and sunlight contributed to soil temperature, the data suggests that sunlight was the more influential driver of soil temperature. These results show that, when planning for soil solarisation during ecological restoration, land managers can benefit by considering sunlight as well as air temperature. The result that sunlight may be the more influential driver of soil temperature empowers land managers to better plan solarisation using sunlight projections, even when temperature is not optimal or is unpredictable.

Management of Fusarium Wilt of Tomato (Fusarium oxysporum f. sp. lycopersici) and Related Soil-borne Diseases using Eco-friendly Methods: A Review

Tomato is rich in vitamins, minerals and contains anti-oxidant compounds, like vitamin C and lycopene that has significant role in human health as it has anti-cancer properties. Tomato production is significantly affected by several factors amongst which Fusarium Wilt is one of the major and widespread fungal soil borne diseases in Nigeria. Difficulty in controlling this disease is attributable to long survivability of the pathogen and its existence in diverse pathogenic races. Conventional strategies, such as the use of resistant cultivars and synthetic fungicides, are not completely effective in managing tomato wilt caused by Fusarium oxysporum f. sp. lycopersici and because of unintended effects of chemicals on the environments its application is highly cautioned. This paper has examined many non-pesticide approaches such as application of bio-control agents, use of suppressive soils, composts/vermicomposts and their extracts, animal manure and urine, soil solarization, botanical extracts, good agricultural practices and integrated disease management strategy to control Fusarium wilt and other related soil borne diseases. It is worth noting that no single method can effectively control such diseases. In order to achieve a sustainable and eco-friendly disease management strategy the use of integrated approach is highly recommended. This review will provide farmers with diverse methods to be integrated as management package for Fusarium wilt and related diseases.

Thermal-Time Hazard Models of Seven Weed Species Germinability following Heat Treatment

Determining the amount of heat units required to kill weed seeds is a crucial aspect for the success of weed control through soil solarization. Lab experiments were designed to determine the duration of exposure for weed seeds that is required to suppress germination at temperatures (40, 45, 50, 55, and 60 °C) in the range of those typically achieved during soil solarization in California. The species tested were annual sowthistle (Sonchus oleraceus L.), bristly oxtongue (Picris echioides L.), nettleleaf goosefoot (Chenopodium murale L.), redroot pigweed (Amaranthus retroflexus L.), common purslane (Portulaca oleracea L.), little mallow (Malva parviflora L.), and redstem filaree (Erodium cicutarium L.). Germination tests were performed to assess the germinability of the weed seeds. The germination suppression by the lab-simulated solarization temperatures differed among the species based on their seasonality. The cool-season annuals S. oleraceus and P. echioides were more susceptible to the heat treatments than the warm-season annuals P. oleracea, A. retroflexus, and C. murale. The hard-seeded weed species M. parviflora and E. cicutarium were the least susceptible to the heat treatments. The germination rates of S. oleraceus, P. echioides, and C. murale were reduced at all of the temperatures that were tested. The germination rates for A. retroflexus and M. parviflora were not affected by temperatures below 40 °C. The germination rates for P. oleracea were not affected by temperature below 45 °C and the germination of E. cicutarium was not affected by any of the temperatures that were tested. The duration (hours) of exposure and percent of germination suppression of the weed seeds were used to create thermal-time hazard models for weed seeds using logistic regression.

Soil solarization as a non-chemical weed control method in tree nursery production systems of the Pacific Northwest, USA

IntroductionHerbicide application in tree nurseries is limited because of the potential for chemical injury to the large diversity of trees species grown, the lack of registered products, and increasing restrictions on herbicide use, necessitating the costly practice of hand weeding. Soil solarization can reduce the weed seedbank by trapping solar energy under clear plastic film, resulting in high soil temperatures lethal to imbibed weed seeds and seedlings. The objective of this study was to determine if soil solarization would be an effective weed management strategy in Pacific Northwest, USA, tree production systems.MethodsField studies were conducted at three commercial tree nurseries in Oregon and Washington over two years to test soil solarization in reducing the naturally occurring weed seedbank and the time required to hand weed fields. Further field and laboratory tests were conducted with five weed species: Poa annua, Polygonum pensylvanicum, Amaranthus retroflexus, Portulaca oleracea, and Cyperus esculentus. Weed seeds and tubers were buried in packets at 5 and 10 cm to determine their viability after 6 weeks of solarization. A laboratory study was conducted with all but C. esculentus to quantify the exposure time at 45, 50, and 55°C required for 90% death (T90).ResultsSoil solarization was particularly effective in reducing the emergence of naturally occurring weeds in the fall and winter, when weed emergence was reduced by 94-96%. Emergence was reduced 67-81% during the subsequent spring and early summer. Nine to ten months after solarization, solarized areas had a 52 – 69% reduction in hand weeding time compared to non-solarized areas. In field trials with buried seed and tuber packets, mortality differed by location and depth, with P. annua and P. pensylvanicum having the greatest percent seed mortality followed by A. retroflexus and variable results for P. oleracea and C. esculentus. In lab studies, seed mortality differed depending on species and temperature; however, at 55°C, there was a relatively rapid drop in seed viability for all species, and T90 values ranged from 1.2 to 41 h whereas at 45°C the range was 47 to > 3000 h. Similar to the field studies, P. annua and P. pensylvancium were more sensitive to heat, followed by A. retroflexus and P. oleracea.ConclusionSoil solarization can be an effective weed management tool in reducing the weed seedbank in Pacific Northwest tree nurseries and other fall-sown crops but may not work for certain, thermotolerant weed species such as C. esculentus.

The identification, characterization, and management of Rotylenchulus reniformis on Cucumis melo in China

The reniform nematode, Rotylenchulus reniformis, is a sedentary root parasite that poses a significant threat to agricultural production in tropical and subtropical regions worldwide. In 2021–2022, a population of R. reniformis was identified in a melon greenhouse in Jimo District, Qingdao, China. To characterize this population, we employed morphological, morphometric, and molecular methods, which confirmed the identity of the nematodes as R. reniformis. Our investigation revealed that R. reniformis successfully infected the roots of melon plants and laid eggs, which could have led to significant crop damage. This report represents the first documented example of R. reniformis infecting melon plants in China. We evaluated several control strategies to combat this nematode, and our results indicated that soil solarization and the use of fosthiazate or chitooligosaccharide copper in combination with soil solarization were effective measures for managing R. reniformis in a greenhouse setting. In addition, combining soil solarization with chitooligosaccharide copper promoted melon plant growth and increased the relative abundance of microorganisms with biocontrol potential.

Impact of Phytopythium vexans on Plant Health: Hosts, Symptoms, Detection, and Management

Abstract Phytopythium vexans is an emerging phytopathogenic oomycete reported to be causing diseases in plants from multiple genera and families. It is a soil and water-inhabiting oomycete with sexual and asexual life cycles present in the environment. Sexual stages produce oospores whereas asexual stages produce zoospores. This pathogen has been reported to be infecting crops in Africa, Asia, Europe, North America, Oceania, and South America. Mainly root and crown regions of numerous perennial woody plants, herbaceous and weedy annual cereal crops, forest plants, ornamental plants, and fruit trees are reported to be infected. Certain names for the symptoms of pathogen infections associated with the host have been used such as replant disease, decline, and sadness syndrome. Young plants that are vegetatively propagated if infected die off in severe cases whereas in the case of older plants, the roots and crown regions are mainly affected by this pathogen. Infections typically display symptoms of brown necrosis in the roots and stem, with a soft, watery rotting mass inside in case of heavily infected samples. Upon gentle pulling, the outer bark sloughs off, revealing the extent of the damage. It also causes damping-off of seedlings. The pathogen moves within water and hence has the potential to induce chains of disease outbreaks in nurseries and greenhouses. A saturated soil for longer periods of time favors tissue colonization and disease progress since the water-loving infectious zoospores of this pathogen can swim to distances that directly favor the pathogen. Higher nitrogen content in the soil, reduced availability of oxygen in the soil, and decreased ability of the plant to grow at lower temperatures created by water stagnation are additional epidemiological factors that favor the disease development. An integrated approach, which includes early detection of the pathogen using culture-based assay/molecular approaches, use of preventive and curative fungicides/biofungicides, and cultural practices, is recommended for the management of Phytopythium . Use of cover crops, soil solarization, crop rotation with non-hosts, and biofumigation to suppress or kill the pathogen are recommended. Testing of irrigation water for the presence of pathogens and treatment using a combination of different measures such as filtration plus UV, ozone, and heat is also recommended. Information © The Authors 2023

Risk assessment of Bacillus cereus in lettuce grown in open-field and greenhouse farming systems in China: A comparative study

Abstract Objectives Bacillus cereus isolates from vegetables can cause diarrheal syndrome food poisoning. Lettuce, the most highly consumed ready-to-eat vegetable, poses a significant risk of B. cereus exposure. Hence, B. cereus monitoring and evaluation during cultivation are essential for preventing foodborne illnesses caused by this food–pathogen combination. However, the impact of different cultivation practices on B. cereus contamination in lettuce currently remains unclear. Furthermore, a validity indicator for the experimental models cannot be effectively validated under field conditions. Materials and Methods Herein, we assessed the risk of B. cereus exposure using lettuce grown under two different cultivation farming systems in China (open-field versus greenhouse) using a quantitative microbial risk assessment model. Tukey’s mean comparison method and kernel density estimation frequency distribution statistics were used for model validation using environmental samples and lettuce. Results The mean concentration of B. cereus in open-field-grown lettuce was significantly higher than that in greenhouse-grown lettuce (P<0.05). No significant differences were observed between measured, formula-calculated, and risk assessment values in environmental samples or lettuce (P>0.05), verifying the accuracy of the risk model. Conclusion Soil solarization, complete manure treatment, usage of mulch films, and irrigation water quality should be considered in agricultural practices to control B. cereus concentrations in lettuce. Overall, we found that B. cereus was more abundant in open-field-grown lettuce, and we provide a risk evaluation framework that can guide farmers and policy-makers to control B. cereus contamination in farm-to-fork lettuce chains in China.