Postharvest Fungicides Research Articles

Profiling Metabolites with Antifungal Activities from Endophytic Plant-Beneficial Strains of Pseudomonas chlororaphis Isolated from Chamaecytisus albus (Hack.) Rothm.

Fungal phytopathogens represent a large and economically significant challenge to food production worldwide. Thus, the application of biocontrol agents can be an alternative. In the present study, we carried out biological, metabolomic, and genetic analyses of three endophytic isolates from nodules of Chamaecytisus albus, classified as Pseudomonas chlororaphis acting as antifungal agents. The efficiency of production of their diffusible and volatile antifungal compounds (VOCs) was verified in antagonistic assays with the use of soil-borne phytopathogens: B. cinerea, F. oxysporum, and S. sclerotiorum. Diffusible metabolites were identified using chromatographic and spectrometric analyses (HPTLC, GC-MS, and LC-MS/MS). The phzF, phzO, and prnC genes in the genomes of bacterial strains were confirmed by PCR. In turn, the plant growth promotion (PGP) properties (production of HCN, auxins, siderophores, and hydrolytic enzymes, phosphate solubilization) of pseudomonads were bioassayed. The data analysis showed that all tested strains have broad-range antifungal activity with varying degrees of antagonism. The most abundant bioactive compounds were phenazine derivatives: phenazine-1-carboxylic acid (PCA), 2-hydroxy-phenazine, and diketopiperazine derivatives as well as ortho-dialkyl-aromatic acids, pyrrolnitrin, siderophores, and HCN. The results indicate that the tested P. chlororaphis isolates exhibit characteristics of biocontrol organisms; therefore, they have potential to be used in sustainable agriculture and as commercial postharvest fungicides to be used in fruits and vegetables.

Peer review of the pesticide risk assessment of the active substance clove oil.

The conclusions of the EFSA following the peer review of the initial risk assessments carried out by the competent authority of the rapporteur Member State, Malta, for the pesticide active substance clove oil are reported. The context of the peer review was that required by Regulation (EC) No 1107/2009 of the European Parliament and of the Council. The conclusions for the amendment of approval were reached on the basis of the evaluation of the representative use of clove oil as a preharvest nematicide on tomatoes and cucumbers (permanent greenhouse use). The representative use evaluated for the renewal of approval of clove oil was as post-harvest fungicide and bactericide on apples, pears and peaches (indoor uses). The reliable endpoints appropriate for use in regulatory risk assessment are presented. Endpoints not relevant to the scope of the proposed amendment of approval conditions will be addressed in the context of the renewal of approval procedure of clove oil running in parallel (AIR IV, EFSA Q-2016-00809). Missing information identified as being required by the regulatory framework is listed. Concerns are reported where identified.

Avirulent Isolates of Penicillium chrysogenum to Control the Blue Mold of Apple Caused by P. expansum.

Blue mold is an economically significant postharvest disease of pome fruit that is primarily caused by Penicillium expansum. To manage this disease and sustain product quality, novel decay intervention strategies are needed that also maintain long-term efficacy. Biocontrol organisms and natural products are promising tools for managing postharvest diseases. Here, two Penicillium chrysogenum isolates, 404 and 413, were investigated as potential biocontrol agents against P. expansum in apple. Notably, 404 and 413 were non-pathogenic in apple, yet they grew vigorously in vitro when compared to the highly aggressive P. expansum R19 and Pe21 isolates. Whole-genome sequencing and species-specific barcoding identified both strains as P. chrysogenum. Each P. chrysogenum strain was inoculated in apple with the subsequent co-inoculation of R19 or Pe21 simultaneously, 3, or 7 days after prior inoculation with 404 or 413. The co-inoculation of these isolates showed reduced decay incidence and severity, with the most significant reduction from the longer establishment of P. chrysogenum. In vitro growth showed no antagonism between species, further suggesting competitive niche colonization as the mode of action for decay reduction. Both P. chrysogenum isolates had incomplete patulin gene clusters but tolerated patulin treatment. Finally, hygromycin resistance was observed for both P. chrysogenum isolates, yet they are not multiresistant to apple postharvest fungicides. Overall, we demonstrate the translative potential of P. chrysogenum to serve as an effective biocontrol agent against blue mold decay in apples, pending practical optimization and formulation.

Postharvest Application of Novel Bio-Based Antifungal Composite Edible Coatings to Reduce Sour Rot and Quality Losses of ‘Valencia’ Oranges

Sour rot, caused by Geotrichum citri-aurantii, can produce significant postharvest losses of citrus fruits and, currently, cannot be effectively controlled by the postharvest fungicides registered in EU countries. Therefore, novel antifungal edible coatings (ECs) based on citrus pectin and beeswax and enriched with eugenol (EG), geraniol (GR), propolis extract (PR) or essential oils (EOs) from Satureja montana (SA), Cinnamomum zeylanicum (CI), or Commiphora myrrha (CM), were developed as alternatives to reduce sour rot and preserve the postharvest quality of ‘Valencia’ oranges. These natural agents were incorporated into the EC formulation and then applied to inoculated oranges. ECs enriched with EG (2–8 g/kg), GR (4 and 8 g/kg), PR (5–20 g/kg), and CM EO (15 g/kg) reduced disease incidence and severity by 75 to 100% compared to uncoated oranges after 20 days of incubation at 20 °C. ECs containing EG (8 g/kg), GR (4 g/kg), and PR (20 g/kg) reduced weight loss and retained firmness of oranges after 14 days of shelf life at 20 °C. Furthermore, all tested ECs maintained the fruit’s sensory and physicochemical quality. Overall, the EG-enriched pectin EC performed best, showing potential as a safe, bio-based alternative to conventional waxes containing synthetic fungicides for the management of citrus postharvest sour rot.

Flow patterns and pathways of legacy and contemporary pesticides in surface waters in tropical volcanic catchments

Severe water pollution issues due to legacy and contemporary pesticides exist in tropical regions and are linked to cash crops requiring intensive plant protection practices. This study aims to improve knowledge about contamination routes and patterns in tropical volcanic settings to identify mitigation measures and analyse risk. To this aim, this paper analyses four years of monitoring data from 2016 to 2019 of flow discharge and weekly pesticide concentrations in the rivers of two catchments grown predominantly with banana and sugar cane in the French West Indies. The banned insecticide chlordecone, applied in banana fields from 1972 to 1993, was still the major source of river contamination, while the currently used herbicide glyphosate, its metabolite aminomethylphosphonic acid (AMPA), and postharvest fungicides also exhibited high contamination levels. A value of 0.5 of the Gustafson Ubiquity Score (GUS) was shown to separate contaminant and noncontaminant pesticides, indicating a high vulnerability to pollution by pesticides in this tropical volcanic context. The patterns and routes of river exposure to pesticides differed markedly between the pesticides in accordance with the hydrological behaviour of volcanic islands and the history and nature of pesticide uses. Concerning chlordecone and its metabolites, observations confirmed previous findings of a main subsurface origin of river contamination by this compound but also showed large erratic short-term variations, suggesting the influence of fast surface transport processes such as erosion for legacy pesticides with large sorption capacity. Concerning herbicides and postharvest fungicides, observations have suggested that surface runoff and fast lateral flow in the vadose zone control river contamination. Accordingly, mitigation options need to be considered differently for each type of pesticide. Finally, this study points out the need for developing specific exposure scenarios for tropical agricultural contexts in the European regulation procedures for pesticide risk assessment.

Efficacy of the cyclolipopeptides fengycin and iturin A against postharvest pome fruit pathogens

Botrytis cinerea (gray mold) and Penicillium expansum (blue mold), are major pome fruit postharvest pathogens and their control relies heavily on the use of one postharvest fungicide (fludioxonil). This study aimed to evaluate the efficacy of the cyclolipopeptides (CLPs), in the form of fengycin and iturin A, in crude metabolite extracts from Bacillus amyloliquefaciens as an alternative biofungicide. The crude extract containing CLPs was applied with an edible coating (i.e., zein as a carrier) as a postharvest treatment against B. cinerea on “Packham’s Triumph” pears and P. expansum on “Cripps Pink” apples. Treatments were applied either as dips in combination with a zein edible coating at pH 2.0 or pH 8.0, or as sprays with a zein edible coating at pH 2.0 or pH 8.0. The efficacy of CLP applications was measured in comparison to the standard registered synthetic fungicide fludioxonil at a concentration of 299.0 mg/L. Treatments were applied to the fruit either preventatively (as sprays) or curatively (as dips or sprays). The lowest mean blue mold incidence (68.6%) was achieved when the edible coating containing the crude extract of B. amyloliquefaciens (CLP at pH 2.0) was applied as a curative dip treatment. B. cinerea infection was reduced by 92.6%, resulting in a 5.7% gray mold incidence for the curative application of CLPs at pH 2.0. This result was not significantly different from the inhibitory action of the fungicide fludioxonil. These results indicate that CLPs are an effective alternative biofungicide that can be used for the control of B. cinerea on pome fruit, especially if their formulation and application are improved and optimized.

Fungicide Resistance of Alternaria alternata and A. arborescens Isolates from Mandarin Fruit and Its Influence on Control of Postharvest Alternaria Rot.

Alternaria rot, caused by Alternaria alternata and A. arborescens, is one of the common postharvest diseases affecting mandarin fruit in California. Fungicide resistance profilings of A. alternata and A. arborescens to quinone outside inhibitors (QoIs), fludioxonil, pyrimethanil, imazalil, and propiconazole were examined in this study. Of the 100 isolates of A. alternata and A. arborescens, 40 were identified as resistant to QoI fungicides according to a PCR-restriction fragment length polymorphism based on a cytochrome b partial gene. Effective concentrations of fludioxonil that caused a 50% reduction in fungal growth relative to the control (EC50) were 0.089 ± 0.020 and 0.101 ± 0.032 µg/ml for 43 A. alternata and 19 A. arborescens isolates, respectively. EC50 values of pyrimethanil, imazalil, and propiconazole for the 70 A. alternata isolates tested were 0.373 ± 0.161, 0.492 ± 0.133, and 1.135 ± 0.407 µg/ml, respectively. EC50 values of pyrimethanil, imazalil, and propiconazole for 30 A. arborescens isolates were 0.428 ± 0.190, 0.327 ± 0.180, and 0.669 ± 0.452 µg/ml, respectively. Control tests on mandarin fruit inoculated with representative isolates of both species showed that fludioxonil, pyrimethanil, imazalil and propiconazole significantly reduced disease incidence and severity. Azoxystrobin significantly reduced Alternaria rot severity and incidence on mandarin fruit inoculated with sensitive isolates but not with resistant isolates, regardless of Alternaria spp. There were no significant differences in Alternaria rot control effectiveness if treatment with any of the fungicides tested was delayed after inoculation by 6 or 12 h. These results could help in the development of postharvest fungicide programs to control Alternaria rot on mandarin fruit during storage.

Evaluation of imazalil dissipation/migration in postharvest papaya using low-temperature partition extraction and GC–MS analysis

Methods involving solid-liquid extraction with low-temperature partition and analysis by gas chromatography coupled to mass spectrometry (GC–MS) were validated to investigate the dissipation/migration of residues of the postharvest fungicide imazalil in papaya skin, pulp, and seeds. The fruits were stored for 23 days (14 °C). Every two days, fruits from the control group and those treated with imazalil had their skin, outer pulp, inner pulp, and seeds separated and then analyzed by GC–MS. After the 23rd day, about 70% of the imazalil had dissipated. Most of the remaining residue was found in the skin; however, the small amount migrating into the pulp was above the maximum residue levels allowed by the regulatory agencies. Imazalil residue was also detected in seeds at concentrations lower than the LOQ (0.025 mg kg−1). Mass loss was the only quality parameter that showed a significant difference between the fruits of the control and study groups.

Tavaborole-Induced Inhibition of the Aminoacyl-tRNA Biosynthesis Pathway against Botrytis cinerea Contributes to Disease Control and Fruit Quality Preservation.

The inhibitory effect of tavaborole on the invasion of Botrytis cinerea in grapes and tomatoes, as well as the potential mechanism involved, was discovered in this study. Our findings showed that tavaborole inhibited Botrytis cinerea spore germination and mycelial expansion in vitro and that the control efficiency in vivo on fruit decay was dose-dependent, which was effective in reducing disease severity and maintaining the organoleptic quality of the fruit, such as reducing weight loss and retaining fruit hardness and titratable acid contents during storage. Furthermore, the precise mechanism of action was investigated further. Propidium iodide staining revealed that Botrytis cinerea treated with tavaborole lost membrane integrity. For further validation, cytoplasmic malondialdehyde accumulation and leakage of cytoplasmic constituents were determined. Notably, the inhibitory effect was also dependent on inhibiting the activities of aminoacyl-tRNA synthetases involved in the aminoacyl-tRNA biosynthesis pathway in Botrytis cinerea. The above findings concluded that tavaborole was effective against Botrytis cinerea infection in postharvest fruit, and a related mechanism was also discussed, which may provide references for the drug repurposing of tavaborole as a postharvest fungicide.

Postharvest Rot of Pomegranate Fruit in Southern Italy: Characterization of the Main Pathogens.

Pomegranate (Punica granatum L.) is an emerging crop in Italy and particularly in southern regions, such as Apulia, Basilicata, and Sicily, due to favorable climatic conditions. The crop is affected by several pathogenic fungi, primarily in the field, but also during postharvest phases. The most important postharvest fungal diseases in pomegranate are gray and blue molds, black heart and black spot, anthracnose, dry rot, and various soft rots. The limited number of fungicides allowed for treatment in the field and the lack of postharvest fungicides make it difficult to control latent, quiescent, and incipient fungal infections. Symptomatic pomegranates from southern Italy were sampled and isolated fungi were morphologically and molecularly characterized. The data obtained revealed that various species of Penicillium sensu lato (including Talaromyces genus), Alternaria spp., Coniella granati, and Botrytis cinerea were the principal etiological agents of postharvest pomegranate fruit diseases; other relevant pathogens, although less represented, were ascribable to Aspergillus sect. nigri, Colletotrichum acutatum sensu stricto, and Cytospora punicae. About two thirds of the isolated pathogens were responsible for latent infections. The results obtained may be useful in planning phytosanitary control strategies from the field to storage, so as to reduce yield losses.

Penicillium spp. - prouzrokovači plave truleži uskladištenih plodova jabuke

Blue mold, caused by the fungal species of genus Penicillium, is one of the most significant post harvest apple diseases. It is estimated that apple blue mold causes multimillion-dollar losses annually. It can affect any apple variety, due to mechanical damage, inadequate protection or storage conditions. Various Penicillium species can cause apple blue mold, but the most significant is Penicillium expansum. Besides economic losses, Penicillium species cause a threat to human health, due to mycotoxin production. To prevent the apple blue mold, the application of preventive measures is necessary, such as careful handling of fruits during harvest, and maintaining hygienic conditions in the storage. Most of the current preharvest fungicides are applied days before harvest and may not be effective in combating this disease, since Penicillium infections usually occur after the harvest. Therefore, post harvest fungicide applications remain the most effective chemical way to control blue mold. In addition to chemical protection, efforts are made to provide efficient biological solutions for the control of this disease. The incidence of apple blue mold is significantly reduced since controlled atmosphere storages are in use, but it still remains the most important post harvest disease of apple fruits.

Assessment of a Postharvest Treatment with Pyrimethanil via Thermo-Nebulization in Controlling Storage Rots of Apples

Apples are very susceptible to infections from various fungal pathogens during the growing season due to prolonged exposure to environmental influences in the field. Therefore, a strict and targeted fungicide strategy is essential to protect fruit and trees. Increased environmental and health concerns and pathogen resistance have resulted in a rising demand to reduce fungicide usage and residues on marketed fruit. Thus, producers must develop new plant protection strategies to conform to the legal and social demands while still offering high-quality apples. This study assessed the efficacy of a post-harvest fungicide treatment with pyrimethanil via thermo-nebulization for controlling storage rots and compared the results to those of standard pre-harvest fungicide strategies. The results showed that a single post-harvest application of pyrimethanil successfully controlled storage rots and is comparable to strategies using multiple pre-harvest fungicide applications. The control of fungal rot was sustained even after 5 months of storage and 2 weeks of shelf life. Thermo-nebulization into the storage facility allowed for a lower dosage of fungicide to be used compared to pre-harvest applications, while still maintaining optimal rot control. Residue analyses showed that the post-harvest fungicide treatment did not exceed legal or retailer’s standards.

Baseline Sensitivity of Alternaria alternata and A. arborescens to Natamycin and Control of Alternaria Rot on Stored Mandarin Fruit.

Alternaria rot caused by Alternaria alternata and A. arborescens is one of the major postharvest diseases on mandarin fruit in California. In this study, natamycin, a newly registered biofungicide, was evaluated for its potential as a postharvest treatment to control Alternaria rot on mandarin fruit. The baseline sensitivities of A. alternata and A. arborescens to natamycin were determined. Effective concentration inhibiting 50% of fungal growth (EC50) values of natamycin for 70 A. alternata isolates ranged from 0.694 to 1.275 µg/ml (mean = 0.921 µg/ml) in a conidial germination assay and from 2.001 to 3.788 µg/ml (mean = 2.797 µg/ml) for 40 A. alternata isolates in a mycelial growth assay. EC50 values of natamycin for 30 A. arborescens isolates ranged from 0.698 to 1.203 µg/ml (mean = 0.923 µg/ml) in a conidial germination assay and from 2.035 to 3.368 µg/ml (mean = 2.658 µg/ml) for 20 A. arborescens isolates in a mycelial growth assay. Control tests on detached mandarin fruit showed that natamycin at both low (460 µg/ml) and high (920 µg/ml) recommended rates significantly reduced disease incidence and severity on mandarin fruit inoculated with Alternaria isolates, regardless of species. High rate of natamycin significantly reduced disease incidence and severity compared with the nontreated control even when natamycin treatment was delayed for 6, 12, and 18 h after inoculation. Our results suggested that natamycin can be an effective postharvest fungicide for control of Alternaria rot on mandarin fruit.

Postharvest Quality Evolution in Long Shelf-Life “Vesuviano” Tomato Landrace

“Vesuviano” or “piennolo” tomato is among the most famous Italian small tomato landraces and is cultivated on the slopes of Vesuvio volcano (Southern Italy). The “piennolo” tomato is an interesting case with regard to its potential sustainability, as it is traditionally grown in water-deficit conditions with a low fertilizer input. Fruits with a high firmness and a thick skin can be stored for 3–4 months at room temperature (“long shelf-life” or LSL tomato) without postharvest fungicide applications. The aim of this research was to study the retention, changes in quality, and nutritional traits of “Vesuviano” tomatoes over 120 days of “natural” storage. The dry matter, soluble sugar, organic acids, volatile compounds, and carotenoid contents were evaluated at harvesting and in fruits stored for 40, 80, and 120 days. Slight decreases in dry matter content, soluble sugars, and sweetness index were found, while the organic acids levels remained relatively stable. Moreover, interesting increases in the concentrations of certain flavor volatiles, alcohols, aldehydes, and terpenes were detected. Regarding carotenoids, the total lycopene levels exhibited a 1.5-fold increase from harvest to 120 days. The unchanged lycopene cis-isomer levels and the β-carotene/total lycopene ratio is characteristic of relatively stable isomerization activity and indicated an optimal ripening pattern up until the end of the “natural” storage period. These results, which demonstrate good overall quality retention of this LSL tomato, represent a well-grounded reason to enhance the cultivation and marketing of this genetic resource, the fruits of which can be appreciated by consumers during the winter–early spring, when high-quality fresh tomatoes are not available on the markets.

Bioprocess performance, transformation pathway, and bacterial community dynamics in an immobilized cell bioreactor treating fludioxonil-contaminated wastewater under microaerophilic conditions

Fludioxonil is a post-harvest fungicide contained in effluents produced by fruit packaging plants, which should be treated prior to environmental dispersal. We developed and evaluated an immobilized cell bioreactor, operating under microaerophilic conditions and gradually reduced hydraulic retention times (HRTs) from 10 to 3.9 days, for the biotreatment of fludioxonil-rich wastewater. Fludioxonil removal efficiency was consistently above 96%, even at the shortest HRT applied. A total of 12 transformation products were tentatively identified during fludioxonil degradation by using liquid chromatography coupled to quadrupole time-of-flight Mass spectrometry (LC-QTOF-MS). Fludioxonil degradation pathway was initiated by successive hydroxylation and carbonylation of the pyrrole moiety and disruption of the oxidized cyanopyrrole ring at the NH-C bond. The detection of 2,2-difluoro-2H-1,3-benzodioxole-4-carboxylic acid verified the decyanation and deamination of the molecule, whereas its conversion to the tentatively identified compound 2,3-dihydroxybenzoic acid indicated its defluorination. High-throughput amplicon sequencing revealed that HRT shortening led to reduced α-diversity, significant changes in the β-diversity, and a shift in the bacterial community composition from an initial activated sludge system typical community to a community composed of bacterial taxa like Clostridium, Oligotropha, Pseudomonas, and Terrimonas capable of performing advanced degradation and/or aerobic denitrification. Overall, the immobilized cell bioreactor operation under microaerophilic conditions, which minimizes the cost for aeration, can provide a sustainable solution for the depuration of fludioxonil-contaminated agro-industrial effluents.

Optimisation of postharvest fungicide application in citrus packhouses: low-tech but high impact

Optimisation of postharvest fungicide application in citrus packhouses: low-tech but high impact

Prevalence and distribution of Penicillium expansum and Botrytis cinerea in apple packinghouses across Washington State and their sensitivity to the postharvest fungicide pyrimethanil

ISHS IV International Symposium on Postharvest Pathology: Next Generation Innovation and Commercial Solutions for Postharvest Pathology to Reduce Losses, Enhance Quality, and Ensure Product Safety Prevalence and distribution of Penicillium expansum and Botrytis cinerea in apple packinghouses across Washington State and their sensitivity to the postharvest fungicide pyrimethanil

Current technologies to control fungal diseases in postharvest papaya (Carica papaya L.)

Papaya ( Carica papaya L.) is a fruit with a natural short shelf life due to its rapid ripening and high susceptibility to fungal diseases, increasing the need for postharvest treatments. The use of heat treatment combined with fungicides in the packinghouse followed by refrigeration during storage and transportation helps to delay the ripening and growth of phytopathogens. However, it is not enough to mitigate the problem, especially when papayas are kept at room temperature. Fungicides are effective to control fungi, but their possible adverse environmental and human health effects have stimulated interest in finding safe and natural substitutes. The purpose of this article is to present the recent advances and trends in the control of postharvest phytopathogens, mainly the use of edible coatings as a safe alternative to preserve and extend the useful life of papaya. The use of biopolymer coatings has gained considerable attention due to their ability to extend the shelf life of fruits. These coatings are a new type of biodegradable primary packaging made from biological compounds such as polysaccharides, proteins, lipids and other polymers. The coatings are considered inert since they form only a physical barrier, separating papayas from their immediate environment, controlling the transfer of gas and moisture. Active coatings can contain supplementary ingredients with additional properties, such as antioxidant and antifungal activity. The application of edible coatings has promising potential to extend papayas' shelf life, in lieu of synthetic fungicides, thus reducing the economic losses from deterioration. • The most important postharvest fungal diseases of papaya are described. • Anthracnose is one of the main concerns related to postharvest papaya. • Alternatives to postharvest fungicides for papaya are discussed. • Edible coatings are the focus for papaya fruit treatment.

Postharvest fungicide sensitivity of South African Botrytis cinerea isolates causing grey mould on pears

ISHS IV International Symposium on Postharvest Pathology: Next Generation Innovation and Commercial Solutions for Postharvest Pathology to Reduce Losses, Enhance Quality, and Ensure Product Safety Postharvest fungicide sensitivity of South African Botrytis cinerea isolates causing grey mould on pears

Mixing postharvest fungicides and sanitizers results in unpredictable survival of microbes that affect cantaloupes

Postharvest treatments with sanitizers and fungicides are applied to increase the quality, safety and shelf life of fresh produce including cantaloupes (also known as rockmelons). The primary role of sanitizers during cantaloupe washing is to prevent cross contamination of potentially pathogenic bacteria in washwater. Postharvest fungicide sprays or dips are employed to inhibit spoilage-causing fungi. While assessing the compatibility of these antimicrobials based on the measurement of active ingredients levels provides some indication of antimicrobial capacity, there is limited data on whether the interaction between these chemicals in wash water modifies their overall efficacy against relevant microorganisms. The aim of this research was to determine how chlorine- and peroxyacetic acid-based sanitizers interact with commercial guazatine- and imazalil-based fungicide formulations used on cantaloupes, and whether mixing these augments or suppresses anti-microbial activity against relevant human pathogens and spoilage fungi in wash water. The results were unpredictable: while most combinations were antimicrobial, the chlorine-based sanitizer when mixed with the guazatine-based fungicide had significantly reduced efficacy against pathogenic Salmonella spp. (~2.7 log) and the fungal spoilage organisms, Trichothecium roseum and Rhizopus stolonifera. Mixing the chlorine-based sanitizer with an imazalil-based fungicide produced a range of outcomes with antagonistic, indifferent and synergistic interactions observed for the fungal species tested. The peroxyacetic acid-based sanitizer led to indifferent interactions with the guazatine-based fungicide, while antagonism and synergy were observed when mixed with the imazalil-based fungicide. This study demonstrates that mixing postharvest agrichemicals used in the cantaloupe industry may increase the risk of microbial contamination and thereby potentially compromise food safety and quality.