Fungal community and toxigenic taxa in chestnut fruits in postharvest conditioning process and storage.

BACKGROUND: Chestnut fruit quality is affected by fungal contamination. The study of the patterns of contamination in the postharvest is crucial to individuate the critical phases and propose solutions. To understand how fungal colonization varies on fruits, the composition of mycobiota was investigated in postharvest handling and in between tissues (shell and kernel). RESULTS: Fungal sequences were clustered into 308 operational taxonomic units (OTUs). Biodiversity was higher in shell than kernel tissues. Results evidenced the risk of new contamination in specific phases such as the 'cold bath' and storage. Genera known as mycotoxin producers were detected in all phases. Specifically, 47 OTUs belonging to Penicillium, eight to Fusarium and two to Aspergillus genera were identified. While Fusarium spp. was sensitive to 'warm bath' phase, Penicillium spp. was largely insensitive and accumulated in storage conditions. Surprisingly, Aspergillus spp. was poorly represented. Aflatoxin, ochratoxin A, fumonisins and T-2/HT-2 detection was performed for shell and kernel, and process phases. Higher contamination was observed on shell than in kernel samples. While aflatoxins were within the European Union (EU) limits for dry fruits, Ochratoxin exceeded the EU limits. The present study represents the first report of fumonisins and T-2/HT-2 detection in chestnuts. CONCLUSION: Fungal contamination taxa is high in chestnut fruits following postharvest handling and storage. A parametrization of process phases such as the 'warm bath' is functional to reduce the risk for some taxa. For other spoilage and mycotoxigenic genera strict sanitation procedures of equipment and water must be individuated and implemented to reduce their impact. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effect of Entomopathogenic Fungi to Eggs and Nymphs Survival of Halyomorpha halys (Hemiptera: Pentatomidae) Under Laboratory Conditions.

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) is becoming a major pest of Greece's agricultural production, including tree fruit. Until now, the control of this pest has been based on conventional methods, with the application of chemical insecticides being the primary option. However, the wide distribution of H. halys, in combination with the large area of tree fruit production in Greece, raise the need for alternative control methods. In this study, we investigated the possibility of implementing microbial control agents for managing H. halys. Eggs and nymphs of H. halys were treated with 15 native entomopathogenic fungal isolates and their virulence was evaluated in the laboratory. After treatment, egg hatching time was recorded for 7 days and ranged from 4.5 to 7.0 days. Nymphal survival was recorded daily for 7 days following application and ranged from 2.1 to 6.6 days for second instar nymphs and 3.7 to 6.8 days for fourth instar ones. Beauveria varroae isolate displayed the highest toxicity to all H. halys stages that were tested and could be considered a promising biocontrol agent of this insect. Please check and confirm that the authors and their respective affiliations have been correctly identified and amend if necessary.οκ.

Analyzing On-Farm Spatiotemporal Distribution of Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) Populations from a Precision Agriculture Perspective.

The brown marmorated stink bug, Halyomorpha halys Stål (Hemiptera: Pentatomidae), is native to Japan, China, Taiwan, and Korea. Its dispersion from Asia to the United States of America and Europe caused serious damage to fruit, vegetables, and high-value crops. In Greece, damages are reported in kiwi orchards in the regions of Pieria and Imathia, which are the main production areas of kiwifruit. Greek kiwifruit production is expected to increase twofold within the next years. The aim of this research is to study the terrain and canopy properties that may have an impact on the development of H. halys populations. Thus, five kiwi orchards in total were selected in the regions of Pieria and Imathia. Τen traps were installed from early June to late October within each selected kiwi orchard-two types of traps at every side of the orchards and the center. The installed traps were examined weekly and the number of the captured H. halys was recorded. During the same days, sentinel satellite images were analyzed to calculate the vegetation index, NDVI (Normalised Difference Vegetation Index), and NDWI (Normalised Difference Water Index). The results showed population variability within the kiwi orchards since the population of H. halys was higher in areas with high NDVI and NDWI values. Additionally, our research revealed that H. halys prefers to develop populations at higher altitudes at both regional and field scales. The results of this research can be used to reduce damages by H. halys in kiwi orchards using different rates of pesticides depending on the prediction of the population size. There are multiple benefits of the proposed practice, such as a reduction in the production cost of kiwifruits, an increase in farmers' profit, and environmental protection.

Impact of 'brown rot' caused by Gnomoniopsis castanea on chestnut fruits during the post-harvest process: critical phases and proposed solutions.

BACKGROUND: The brown rot fungus, Gnomoniopsis castanea, is the main organism responsible for the outbreak of chestnut postharvest decay that is threatening the sustainability of the chestnut market in Europe. Currently, no specific strategy is available to mitigate the impact and remediate the high losses of fruits in postharvest storage. In the present study, the different phases of chestnut handling in a standard facility plant were analyzed by evaluating the amount of fruit rot and infection by G. castanea at each phase. RESULTS: The warm bath (48 °C) was identified as the critical phase, requiring strict parametrization to effectively inactivate G. castanea in fruits. Laboratory tests indicated that maintaining fruits at 50 °C for a maximum of 45 min provided optimal conditions to completely inactivate G. castanea inoculum during postharvest handling. However, the warm bath at 50 °C and over was not effective in inactivating the complex of fungal taxa responsible for contamination and development of molds. Higher temperatures and extended treatment times caused significant losses in fruit quality, as indicated by taste panel evaluation. Upscaling of postharvest facilities is discussed and critically evaluated. CONCLUSION: The warm bath (50 °C for 45 min) is effective in completely inactivating G. castanea in fruits but did not reduce the impacts of the complex of molds responsible for external contamination and mycotoxin production. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

First Report of Native Parasitoids of Halyomorpha halys (Hemiptera: Pentatomidae) in Greece.

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) is an endemic species of East Asia; it was introduced into Europe in 2007. It has a wide range of hosts as it feeds on over 170 host plant species and significantly impacts crop production. In Greece, H. halys causes significant losses in the production of kiwi, peaches, and green beans; thus, control of this species (including biological control) is essential. Here, we focus on the potential impact of native natural enemies of H. halys in Greece. From June to October 2020, we sampled naturally field-laid H. halys egg masses to recover native parasitoids. A total of 20 egg masses of H. halys were collected from infested fields from different locations in northern Greece. Out of 529 eggs, 45 parasitoids managed to hatch successfully. The overall parasitism rate was 8.5%. We found two species of Hymenopteran egg parasitoids attacking H. halys eggs-Anastatus bifasciatus (Geoffrey) (Hymenoptera: Eupelmidae) and Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae), with the former comprising 58% of all parasitoids that were recovered. These results contribute to the knowledge about the natural enemy community that attacks H. halys in Greece, and the use of these native egg parasitoids in biological control programs may be a viable H. halys management strategy.

A Temperature Conditioned Markov Chain Model for Predicting the Dynamics of Mosquito Vectors of Disease.

Understanding and predicting mosquito population dynamics is crucial for gaining insight into the abundance of arthropod disease vectors and for the design of effective vector control strategies. In this work, a climate-conditioned Markov chain (CMC) model was developed and applied for the first time to predict the dynamics of vectors of important medical diseases. Temporal changes in mosquito population profiles were generated to simulate the probabilities of a high population impact. The simulated transition probabilities of the mosquito populations achieved from the trained model are very near to the observed data transitions that have been used to parameterize and validate the model. Thus, the CMC model satisfactorily describes the temporal evolution of the mosquito population process. In general, our numerical results, when temperature is considered as the driver of change, indicate that it is more likely for the population system to move into a state of high population level when the former is a state of a lower population level than the opposite. Field data on frequencies of successive mosquito population levels, which were not used for the data inferred MC modeling, were assembled to obtain an empirical intensity transition matrix and the frequencies observed. Our findings match to a certain degree the empirical results in which the probabilities follow analogous patterns while no significant differences were observed between the transition matrices of the CMC model and the validation data (ChiSq = 14.58013, df = 24, p = 0.9324451). The proposed modeling approach is a valuable eco-epidemiological study. Moreover, compared to traditional Markov chains, the benefit of the current CMC model is that it takes into account the stochastic conditional properties of ecological-related climate variables. The current modeling approach could save costs and time in establishing vector eradication programs and mosquito surveillance programs.

Evaluation of Two Predictive Models for Forecasting Olive Leaf Spot in Northern Greece.

Olive leaf spot (Venturia oleaginea) is a very important disease in olive trees worldwide. The introduction of predictive models for forecasting the appearance of a disease can lead to improved disease management. One of the aims of this study was to investigate the effect of temperature and leaf wetness on conidial germination of local isolates of V. oleaginea. The results showed that a temperature range of 5 to 25 °C was appropriate for conidial germination, with 20 °C being the optimum. It was also found that at least 12 h of leaf wetness was required to start the germination of V. oleaginea conidia at the optimum temperature. The second aim of this study was to validate the above generic model and a polynomial model for forecasting olive leaf spot disease under the field conditions of Potidea Chalkidiki, Northern Greece. The results showed that both models correctly predicted infection periods. However, there were differences in the severity of the infection, as demonstrated by the goodness-of-fit for the data collected on leaves of olive trees in 2016, 2017 and 2018. Specifically, the generic model predicted lower severity, which fits well with the incidence of the disease symptoms on unsprayed trees. In contrast, the polynomial model predicted high severity levels of infection, but these did not fit well with the incidence of disease symptoms.

Studies on Diaporthe eres as a New Pathogen of Peach Trees in Greece.

Phomopsis sp., the imperfect stage of the genus Diaporthe, is an increasingly common fungal pathogen of peach (Prunus persica). This study is the first report of the occurrence of a shoot blight and canker disease of peach in Greece caused by the fungus Diaporthe eres. The pathogen caused distinct cankers with abundant gumming on shoots of peach and nectarine trees. The rate of development of D. eres in vitro was reduced as temperatures increased from 25 to 30°C or decreased from 25 to 15°C, and was totally inhibited at 35 and 10°C. Storage at 10°C of peach fruit inoculated with D. eres controlled the development of fruit rot. Pathogenicity tests showed that 27 peach and nectarine cultivars grown in Imathia Prefecture, Greece, were equally susceptible to D. eres. The fungicides thiophanate methyl, carbendazim, tebuconazole, iprodione, and the mixture of cyprodinil:fludioxonil were evaluated against the development of D. eres and the disease symptoms. Thiophanate methyl, carbendazim, and tebuconazole significantly inhibited the growth of D. eres whereas iprodione and the mixture of cyprodinil:fludioxonil were less effective in inhibiting mycelial growth and disease symptoms. The sensitivity of 24 isolates of D. eres to carbendazim, thiophanate methyl, and tebuconazole was also tested. The results showed that most of the isolates used were sensitive to these fungicides, with some isolates showing a level of insensitivity. In general, the disease caused by D. eres could be a threat for peach cultivation in Greece and its management should be investigated in the field.