Peach Orchards Research Articles

Bee Diversity and Abundance During Peach Bloom in South Carolina, United States

ABSTRACTPeach (Prunus persica [L.] Batsch) is an important speciality fruit crop in the United States. Peach is self‐compatible, but bee pollination enhances fruit sets and diverse populations improve pollination efficiency. However, the bee diversity and abundance in peach orchards in South Carolina are unknown. To understand this, we sampled bees during peach tree bloom at two locations in South Carolina—the Clemson University Musser Fruit Research Center (MFRC) and a peach farm in Ridge Spring, South Carolina. Overall, a total of 651 bees were collected from peach orchards, of which Bombus (37%) and Apis (32%) were the most dominant genera, followed by Eucera (14%), Andrena (8%) and Habropoda (5%). Diversity indices indicate higher species richness and diversity at the Ridge Spring farm than at MFRC. Dominant species at the MFRC were Apis mellifera (36.77%), Bombus bimaculatus (29.1%), B. griseocolis (12%) and Eucera hamata (8%). In contrast, the Ridge Spring farm was dominated by A. mellifera (24.17%), Habropoda laboriosa (12%), Andrena barbara (12%), E. atriventris (11.72%) and B. bimaculatus (11.35%). In comparing the effectiveness of sampling methods, blue vane traps (BVTs) captured more bees than aerial sweep netting. Furthermore, BVTs predominantly captured larger‐sized bees, while smaller‐sized bees were more frequently collected using sweep netting. Throughout peach bloom, differences in bee abundance were observed over time as well. Our study sheds light on the bee diversity and abundance in South Carolina peach orchards, revealing variations between locations. This knowledge of bee diversity and abundance will provide baseline information on bee communities in peach orchards and will help develop suitable pollinator conservation programs.

Responses of 'Flordaguard' and 'MP-29' Prunus spp. rootstocks to hypoxia and high root zone temperature.

Selecting the right rootstock is crucial for successful fruit production and managing both biotic and abiotic stresses in commercial fruit orchards. To enhance the resilience of peach orchards, this study evaluated the physiological and biochemical responses of Prunus spp. rootstocks , 'Flordaguard' and 'MP-29,' under normoxia (sufficient oxygen content) or short-term hypoxia (low-oxygen content) and ambient or high temperature (40°C) in the root zone. Physiological responses measured were net photosynthesis, stomatal conductance, transpiration, intercellular CO2 concentration, water use efficiency, the leaf chlorophyll index, and the maximum potential quantum efficiency of photosystem II. The leaf concentrations of nitrogen, phosphorus, potassium, magnesium, calcium, sulfur, boron, zinc, manganese, iron, and copper were also analyzed. Reactive oxygen species (ROS) and antioxidants analyzed were superoxide dismutase (SOD) activity, peroxidase (POD) activity, catalase (CAT) activity, ascorbate peroxidase (APX) activity, glutathione peroxidase (GPX) activity, proline content, glycine betaine content (GB), lipid peroxidation (LPO), superoxide (O2 -) concentration, and hydrogen peroxide (H2O2) concentration. When subjected to root zone hypoxia or high temperature individually, 'MP-29' performed better physiologically than 'Flordaguard'. However, when root zone hypoxia and high temperature were combined, 'MP-29' performed better biochemically with enhanced antioxidant activity, osmolyte content, and nutrient absorption. Nutrient analysis of leaves revealed that 'MP-29' had higher N, P, K, Ca, and B concentrations than 'Flordaguard'. Consequently, 'MP-29' demonstrated greater tolerance to short-term exposure to the combined effects of high root zone temperature and hypoxia. This research contributes to identifying a suitable rootstock within the Prunus genus able to withstand root zone conditions that often result from severe weather events commonly experienced in Florida and other parts of the world.

Seasonal activity of plum curculio (Coleoptera: Curculionidae) in small Southeastern peach orchards.

Plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), is a key pest in Southeastern peach production by infesting fruit and decreasing yield. In Northeastern apples, plum curculio was found to have an "edge effect," where more plum curculio are present next to a forested border than in the center of an orchard, and their propensity to fly or walk depended on air temperature. We conducted field studies over 3 seasons (2019-2021) to investigate whether plum curculio in small Southeastern peach plots exhibits the edge effect and to determine its primary mode of movement (flying or walking). Our results revealed that plum curculio did not exhibit the edge effect in Southeastern peaches. Thus, unlike Northeastern apples where plum curculio exhibits the edge effect, the reduced-input application program where insecticide sprays mainly target a few perimeter-row trees instead of the whole orchard for plum curculio management is not recommended for Southeastern peaches. Additionally, we observed that plum curculio in Southeastern peaches did not exhibit a primary mode of movement, and in most of the sampling weeks, the numbers of flying and walking plum curculio were not significantly correlated in the field. These results emphasize that using plum curculio sampling tools that only capture flying or walking plum curculio is not ideal for monitoring plum curculio activity in the Southeast. Overall, our findings indicate that plum curculio in Southeastern small peach plots and Northeastern apples does not exhibit the same behavior (i.e., edge effect and propensity to fly or walk).

Phosphorus-induced restructuring of the ascorbate-glutathione cycle and lignin biosynthesis alleviates manganese toxicity in peach roots.

Manganese (Mn) is indispensable for plant growth, but its excessive uptake in acidic soils leads to toxicity, hampering food safety. Phosphorus (P) application is known to mitigate Mn toxicity, yet the underlying molecular mechanism remains elusive. Here, we conducted physiological and transcriptomic analyses of peach roots response to P supply under Mn toxicity. Manganese treatment disrupted root architecture and caused ultrastructural damage due to oxidative injury. Notably, P application ameliorated the detrimental effects and improved the damaged roots by preventing the shrinkage of cortical cells, epidermis and endodermis, as well as reducing the accumulation of reactive oxygen species (ROS). Transcriptomic analysis revealed the differentially expressed genes enriched in phenylpropanoid biosynthesis, cysteine, methionine and glutathione metabolism under Mn and P treatments. Phosphorus application upregulated the transcripts and activities of core enzymes crucial for lignin biosynthesis, enhancing cell wall integrity. Furthermore, P treatment activated ascorbate-glutathione cycle, augmenting ROS detoxification. Additionally, under Mn toxicity, P application downregulated Mn uptake transporter while enhancing vacuolar sequestration transporter transcripts, reducing Mn uptake and facilitating vacuolar storage. Collectively, P application prevents Mn accumulation in roots by modulating Mn transporters, bolstering lignin biosynthesis and attenuating oxidative stress, thereby improving root growth under Mn toxicity. Our findings provide novel insights into the mechanism of P-mediated alleviation of Mn stress and strategies for managing metal toxicity in peach orchards.

A Machine Learning Approach to Monitor the Physiological and Water Status of an Irrigated Peach Orchard under Semi-Arid Conditions by Using Multispectral Satellite Data

Climate change is making water management increasingly difficult due to rising temperatures and unpredictable rainfall patterns, impacting crop water availability and irrigation needs. This study investigated the ability of machine learning and satellite remote sensing to monitor water status and physiology. The research focused on predicting different eco-physiological parameters in an irrigated peach orchard under Mediterranean conditions, utilizing multispectral reflectance data and machine learning algorithms (extreme gradient boosting, random forest, support vector regressor); ground data were acquired from 2021 to 2023 in the south of Italy. The random forest model outperformed in predicting net assimilation (R2 = 0.61), while the support vector machine performed best in predicting electron transport rate (R2 = 0.57), Fv/Fm ratio (R2 = 0.66) and stomatal conductance (R2 = 0.56). Random forest also proved to be the most effective in predicting stem water potential (R2 = 0.62). These findings highlighted the potential of integrating machine learning techniques with high-resolution satellite imagery to assist farmers in monitoring crop health and optimizing irrigation practices, thereby addressing the challenges determined by climate change.

Assessing the composition and abundance of beneficial fauna trapped in Ceratitis capitata (Diptera: Tephritidae) traps in peach orchards in Tunisia

Experiment on trapping non-target arthropods in conventional delta traps baited with Ceratitis capitata (Wiedemann, 1824) female attractant was undertaken in multi-variety peaches orchards in the north East of Tunisia during the cultivation season (from May 2022 to September 2022). Hence, 24 Delta traps having white sticky panels were placed in the experimental site and inspected generally at weekly interval. Captured insects were determined to family level visually using a manual magnifying glass when possible, or gently removed and identified in the laboratory under binocular microscope either on family or species levels. Results indicated that traps attracted very low number of non-target arthropods compared to Mediterranean fruit fly adults. Collected species belonged to families: Apidae, Halictidae, Colletidae, Megachilidae, Braconidae, Ichneumonidae, Scelionidae, Pteromalidae, Torymidae, Chalcididae, Eucoilidae, Syrphidae, Pompilidae, Crabronidae, Coccinellidae, Chrysopidae and Formicidae. In total, more than 700 adults of Chrysoperla carnea (Stephens, 1836) were attracted and 53 % of captured individuals are parasitic wasp species belonging particularly to Pteromalidae and Scelionidae families. Compared to the highest level of MedFly capture, the effect of delta traps baited with the female attractants on beneficials can be considered as insignificant (Kruskal-Wallis test ANOVA H = 35.6947, P < 0.00001). Hence, trapping grid can be used to monitor the population of MedFly without hazardous effects on beneficial insect fauna.

Prerequisites for cultivating frost-resistant peach varieties in the Right-Bank part of the Western Forest-Steppe of Ukraine

The necessity of cultivating frost-resistant peach varieties in the Forest-Steppe zone of Ukraine arises due to frequent sharp fluctuations in air temperature during the winter-spring period. Their cultivation can mitigate the impact of weather conditions, ensuring stable fruit production of this crop. The study aimed to analyse the prospects for growing peaches (Prunus persica Mill.) using intensive technologies under changing climate conditions. An analysis of the peach-growing situation revealed that it is a widely cultivated drupe in Ukraine and globally. The main countries leading in peach fruit production were identified: China, Italy, Turkey, Greece, and Spain. Despite a 24% increase in global peach production between 2013 and 2023, the demand for this crop has also risen, leading to a deficit and increased imports to Ukraine. Calculations of the scientifically justified annual consumption norms for peaches showed a shortfall of 187 thousand tonnes in production, with current production standing at 11.2 thousand tonnes. Several factors hindering the expansion of peach orchards were identified. The development of frost-resistant varieties by breeders, suitable for cultivation in the Forest-Steppe of Ukraine, alongside changing weather conditions, offers opportunities for the safe cultivation of peaches in the region. An analysis of the weather conditions in the Right-Bank part of the Western Forest-Steppe of Ukraine was conducted. It was found that between 2013 and 2023, there was a significant increase in the total active temperatures, with 2023 recording a maximum of 3,777°C. At the same time, precipitation decreased by 58%, amounting to only 325 mm. Considering the changing weather conditions and the development of new frost-resistant varieties, which have expanded the peach cultivation zone to northern regions of Ukraine, it is essential to prepare and implement specific measures to adapt the horticultural industry to peach cultivation in these new regions to meet domestic market demands. It is recommended to initiate trials in irrigated horticulture and develop new methodological guidelines to provide scientific support for establishing perennial peach orchards in the Right-Bank part of the Western Forest-Steppe of Ukraine

Comparative Fitness of Monilinia fructicola Isolates with Multiple Fungicide-Resistant Phenotypes.

This study characterized 52 isolates of Monilinia fructicola from peach and nectarine orchards for their multiresistance patterns to thiophanate-methyl (TF), tebuconazole (TEB), and azoxystrobin (AZO) using in vitro sensitivity assays and molecular analysis. The radial growth of M. fructicola isolates was measured on media amended with a single discriminatory dose of 1 μg/ml for TF and AZO and 0.3 μg/ml for TEB. Cyt b, CYP51, and β-tubulin were tested for point mutations that confer resistance to quinone outside inhibitors (QoIs), demethylation inhibitors (DMIs), and methyl benzimidazole carbamates (MBCs), respectively. Eight phenotypes were identified, including isolates with single, double, and triple in vitro resistance to QoI, MBC, and DMI fungicides. All resistant phenotypes to TF and TEB presented the H6Y mutation in β-tubulin and the G641S mutation in CYP51. None of the point mutations typically linked to QoI resistance were present in the Monilinia isolates examined. Moreover, fitness of the M. fructicola phenotypes was examined in vitro and in detached fruit assays. Phenotypes with single resistance displayed equal fitness in vitro and in fruit assays compared with the wild type. In contrast, the dual- and triple-resistance phenotypes suffered fitness penalties based on osmotic sensitivity and aggressiveness on peach fruit. In this study, multiple resistance to MBC, DMI, and QoI fungicide groups was confirmed in M. fructicola. Results suggest that Monilinia populations with multiple resistance phenotypes are likely to be less competitive in the field than those with single resistance, thereby impeding their establishment over time and facilitating disease management.

Effects of returning peach branch waste to fields on soil carbon cycle mediated by soil microbial communities.

In recent years, the rise in greenhouse gas emissions from agriculture has worsened climate change. Efficiently utilizing agricultural waste can significantly mitigate these effects. This study investigated the ecological benefits of returning peach branch waste to fields (RPBF) through three innovative strategies: (1) application of peach branch organic fertilizer (OF), (2) mushroom cultivation using peach branches as a substrate (MC), and (3) surface mulching with peach branches (SM). Conducted within a peach orchard ecosystem, our research aimed to assess these resource utilization strategies' effects on soil properties, microbial community, and carbon cycle, thereby contributing to sustainable agricultural practices. Our findings indicated that all RPBF treatments enhance soil nutrient content, enriching beneficial microorganisms, such as Humicola, Rhizobiales, and Bacillus. Moreover, soil AP and AK were observed to regulate the soil carbon cycle by altering the compositions and functions of microbial communities. Notably, OF and MC treatments were found to boost autotrophic microorganism abundance, thereby augmenting the potential for soil carbon sequestration and emission reduction. Interestingly, in peach orchard soil, fungal communities were found to contribute more greatly to SOC content than bacterial communities. However, SM treatment resulted in an increase in the presence of bacterial communities, thereby enhancing carbon emissions. Overall, this study illustrated the fundamental pathways by which RPBF treatment affects the soil carbon cycle, providing novel insights into the rational resource utilization of peach branch waste and the advancement of ecological agriculture.

Effect of Partial Substitution of Chemical Fertilizers with Organic Fertilizers on N2O and NO Emissions from a Peach Orchard

Organic fertilizer substitution has been promoted as a weight loss, efficient, and diversified fertilizer substitution technology in agricultural production. However, there is a lack of comprehensive assessment of the impact of organic fertilizers on N2O and NO emissions from orchards. In this study, N2O and NO emissions from peach orchards were observed annually using static dark box-gas chromatography to compare the effects of chemical fertilizer application alone and partial replacement of chemical fertilizer treatment on NO emissions from peach orchards. The results showed that the partial replacement of chemical fertilizers with organic fertilizers reduced the total N2O and NO emissions from peach orchards by 15.0 % and 9.4 %, respectively. The N2O and NO emission factors were reduced by 21.3 % and 21.1 %. The mineral N content of the soil in the organic fertilizer treatment was lower than that in the chemical fertilizer treatment alone. The organic fertilizer treatment increased the contribution of AOA to nitrification and decreased the contribution of AOB, thus reducing N2O and NO from nitrification. In addition, the results of the dual isotope mixing model[δ18O(N2O/H2O) vs. δ15NSP] indicated that the bacterial denitrification/nitrifying bacterial denitrification (bD/nD) process served as the primary pathway for N2O emissions in peach orchards. Partial substitution with organic fertilizers enhanced soil denitrification, resulting in larger reductions in the amounts of N2O and NO. Therefore, partial substitution of organic fertilizer is a viable measure to mitigate nitrogen oxide emissions from orchards and to achieve green and low-carbon development in agriculture.

Investigation on the effect of “Panatechnology” products on some aphids in orchards

The products of the Panatechnology series are completely natural, obtained by finely grinding rock meal and adding other natural ingredients. They can be applied as complex foliar and soil fertilizers and as agents increasing the natural immunity of plants. The aim of the investigation was to determine the potential effect of these products on some aphids in apple and peach orchards. The study was conducted in 2022 and 2023 in conventional orchards of apples and peaches, in the experimental fields of the Agricultural University – Plovdiv. Several leaf treatments were carried out with products from the Panamin and Panatop series (Immuno Save; Panamin Suspension, etc.) as a comprehensive program to improve plant resistance and growth during the spring period. The experiments have shown that Panamin and Panatop immunostimulants can reduce the rate of attack of some aphids on apple and peach trees to some extent but cannot completely prevent the danger of these pests, especially in a year suitable for their development.

First Report of Calosphaeria pulchella causing Canker and Twig Dieback of Peach (Prunus persica) in California, U.S.A.

California leads the United States in peach (Prunus persica L.) production, with approximately 505,000 tons produced in 2021 and valued at $378.3 million (California Agriculture Statistics Review, 2021-2022). During the spring and summer of 2023, twig and branch dieback were observed in three peach orchards (cvs. Late Ross and Starn) in San Joaquin County, California. Wood cankers and discoloration also occurred in branches, generally initiating at pruning wounds. Approximately 8 symptomatic twigs or branches per orchard were collected to proceed with the isolation of necrotic tissues on acidified potato dextrose agar (APDA). Isolations consistently yielded colonies of the fungal pathogen Calosphaeria pulchella (Pers. : Fr.) J. Schröt. (Réblová et al. 2004; Trouillas et al. 2012). Pure cultures were obtained by transferring single hyphal tips onto new APDA Petri plates. Colonies on APDA grew dark pink to red or purple in their center, with a white margin. Conidiogenesis was phialidic, producing round conidial masses at the tip of phialides. Conidia were produced abundantly on APDA, and were hyaline, allantoid to oblong-ellipsoidal, 4 to 5.5 (7) × 1.2 to 2.3 μm (n = 60). Two representative isolates (SJC-62 and SJC-64) were selected for genomic DNA extraction and sequencing of the internal transcribed spacer region (ITS) using ITS5/ITS4 universal primers and the beta-tubulin (TUB2) gene region using primers Bt2a and Bt2b. Consensus sequences of the two genes for the two isolates (ITS: PP063990, PP063991; TUB2: PP068303, PP068304) were compared to reference sequences (Réblová et al. 2015; Trouillas et al. 2012) using BLAST analysis. The ITS sequences of SJC-62 and SJC-64 were 99.8 and 99.5% identical to that of C. pulchella ex-type strain CBS 115999 (NR145357) and reference strain SS07 (HM237297); the TUB2 sequences were at least 98.5% identical to that of C. pulchella CBS 115999 (KT716476). Pathogenicity tests were conducted in 2- to 3-year-old healthy branches on 7-year-old peach trees, cvs. Loadel, Late Ross and Starn using the two fungal isolates and a control treatment (1 branch per treatment and 3 branches per tree) on each of 8-tree replicates. Branches were inoculated in June 2023 following wounding with a 5 mm cork borer to remove the bark and placing an agar plug from the margin of 10-day-old colonies on APDA directly into the fresh wound. Sterile agar plugs were used as controls. Inoculation sites were covered with petroleum jelly and wrapped with Parafilm to retain moisture. The experiment was completed twice. After four months, cankers and vascular discolorations developed around the inoculation sites. Length of vascular discoloration in inoculated branches averaged 72, 75, and 79 mm, for the Loadel, Starn, and Late Ross cvs., respectively. Calosphaeria pulchella was re-isolated from inoculated branches at 80 to 100% recovery rate, thus fulfilling Koch's postulates. The average length of vascular discoloration in the control was 13.5 mm and no fungi were recovered from control branches. Calosphaeria canker caused by C. pulchella is a global disease of sweet cherry. Recently, it was reported to cause cankers in peach trees in Chile (Grinbergs et al. 2023). To our knowledge, this is the first report of C. pulchella causing cankers and twig dieback of peach trees in the United States. These findings improve our knowledge of the etiology of canker diseases affecting peach trees and is critical for the development of effective disease management strategies.

Hover fly (Diptera: Syrphidae) diversity and seasonality in North Georgia apple and peach orchards.

Crop pollination and natural biological control provided by beneficial insects have an economic worth of hundreds of billions of dollars annually. Apple and peach production in North Georgia are economically important industries that benefit from these ecological services. Hover flies are dual ecosystem service providers that have been relatively understudied in orchard ecosystems. We investigated the diversity and seasonal activity of hover flies in apple and peach orchards at 2 sites in North Georgia from March to October 2020 and 2021. Bowl traps were used to sample hover flies in orchard edge and interior habitats. The aphidophagous species Toxomerus geminatus (Say) (Diptera: Syrphidae) and Toxomerus marginatus (Say) (Diptera: Syrphidae) comprised 86.6% of the total hover flies collected. Apple orchards yielded the greatest hover fly presence, species richness, and Toxomerus spp. abundance. Hover fly richness and diversity were greatest during postbloom, but Toxomerus spp. abundance was greatest during the bloom period. No differences in presence, richness, diversity, or Toxomerus spp. abundance were found between edge and interior habitats. Toxomerus geminatus and T. marginatus were dominant from March through August, with T. geminatus being more abundant than T. marginatus in March, early April, and August. October sampling produced the greatest hover fly richness. Our results suggest that hover flies are abundant in North Georgia orchards and exhibit substantial spatial and temporal variation in richness and diversity. Expanded studies incorporating additional sampling efforts and methods are needed to further characterize the hover fly fauna and their impact on North Georgia apple and peach orchards.

Environmental transport of excess nitrogen fertilizer in peach orchard: Evidence arising from 15N tracing trial

In pursuit of high fruit yield, overwhelming amount of nitrogen (N) fertilizer was unreasonably applied in orchard, resulting in lower fertilizer N uptake and higher environmental loss. It is crucial to propose appropriate fertilization timing and optimal N management by clarifying fruit tree N uptake pattern in orchard systems. Here, a 15N isotope enrichment trial was conducted in peach orchard to assess the transport of applied synthesized fertilizer-N to the plant and environment in the Taihu Lake region. Ammonium sulfate ((NH4)2SO4, 10.12 atom % 15N), as the N source, was applied with four split applications at 382.5 kg N ha−1 during one plant growth cycle. Results showed N deriving from fertilizer (NDFF) accounted for 24.5% in leaves and 38.4% in fruits, respectively. During the annual growth cycle, the applied fertilizer-N uptake and utilization was higher in reproductive growth stage than vegetative growth stage. After harvest, 28.8% of applied fertilizer-N was absorbed by peach tree, 9.5% was lost to the environment through surface runoff, ammonia (NH3) volatilization and nitrous oxide (N2O) emission, 29.6% was retained in the 0–160 cm soil profile, the remaining 32.1% was unaccounted N including N leaching and N loss from the N removal progress. Generally, more applied fertilizer-N moved to the environment in high N input peach orchard. In order to promote optimal N management, the applied fertilizer-N rate should be reduced by 30% and emphasized on fertilization at the reproductive growth period according to tree N uptake pattern.

Staphylococcus warneri, an unconventional plant pathogen involved in canker disease of almond and other Prunus species

AbstractBacterial canker disease of stone fruits is a major concern in stone fruit‐growing countries worldwide. Pseudomonas spp. and Xanthomonas arboricola pv. pruni (Xap) are the primary pathogens involved in this disease. In spring, summer and autumn 2016, symptoms like those produced by Pseudomonas spp. and Xap were observed in almond, apricot, peach and nectarine orchards in central provinces of Iran (Qom, Isfahan, and Chaharmahal and Bakhtiari). Gram‐positive cocci bacterial isolates were obtained from symptomatic trees. Following hypersensitivity and pathogenicity tests, isolates were divided into pathogenic and nonpathogenic groups, demonstrating the pathogenicity of some isolates on saplings of almond, peach and apricot. Multilocus sequence analysis was performed using the partial sequence of 16S rRNA region and four housekeeping genes, namely tuf, gap, dnaJ and rpoB, to determine the taxonomic classification of isolates, and revealed that pathogenic isolates identified as Staphylococcus warneri, while nonpathogenic isolates identified as S. warneri, S. epidermidis, S. hominis and S. saprophyticus. The isolates were further characterized by phenotypic and biochemical tests as well as by antibiotics assays. The unusual nature of the identified microorganism in the present study lies in the fact that, unlike most plant‐pathogenic agents, S. warneri is recognized worldwide as a cause of bacterial infections in humans and animals. Taken together, the bacterial canker disease caused by S. warneri appears to be a newly emerging disease of apricot, peach and almond trees.

Application of an improved U-Net with image-to-image translation and transfer learning in peach orchard segmentation

Peach cultivation holds a significant economic importance, and obtaining the spatial distribution of peach orchards is helpful for yield prediction and precision agriculture. In this study, we introduce a new U-Net semantic segmentation model, utilizing ResNet50 as a backbone network, augmented with an Efficient Multi-Scale Attention (EMA) mechanism module and a LayerScale adaptive scaling parameter. To address style differences between images from Unmanned Aerial Vehicle (UAV), Google Earth, and Sentinel-2 satellite, we incorporate Cycle-Consistent Generative Adversarial Networks (CycleGAN). This synthesis ensures that UAV images conform to a comparable style found in Google Earth and Sentinel-2 images, while feature details of high spatial resolution UAV images are transferred to Google Earth and Sentinel-2 images through transfer learning. The results demonstrate that using ResNet50 as a backbone network for the U-Net model yields higher accuracy compared to using VGG16 for the U-Net model. Specifically, the Mean Intersection over Union (MIoU) values for UAV and Sentinel-2 images are higher by 0.49 % and 0.95 %, respectively. The MIoU values for UAV, Google Earth, and Sentinel-2 images increased by 0.87 %, 1.71 %, and 1.74 %, respectively, with the introduction of EMA. Additionally, with the introduction of LayerScale adaptive scaling parameters, the MIoU values increased by 0.31 %, 0.33 %, and 1.44 %, respectively, further enhancing the segmentation accuracy of the model. After applying CycleGAN and transfer learning, the MIoU increased by 1.02 %, 0.15 %, and 1.57 % for UAV, Google Earth, and Sentinel-2 images, respectively, resulting in MIoU values of 97.39 %, 92.08 %, and 84.54 %. The comparative analysis with DeepLabV3+, PSPNet, and HRNet models demonstrates the superior mapping performance of the proposed method. Moreover, the method exhibits good generalization and mapping speed across six test sites in the research area. Overall, this approach ensures high precision and efficiency in peach orchard mapping, accommodating various spatial resolutions, and holds potential for addressing diverse requirements in peach orchard mapping applications.

Multi-Agent target allocation and safe trajectory planning for artificial pollination tasks

This paper presents an autonomous multi-agent drone system utilized for an artificial pollination task to address the declining bee population and its impact on natural pollination. The main goal is to visit all the targets (flowers) by drones. The system receives the position of the targets located on a vertical fruiting wall from a single sensor mounted on an unmanned ground vehicle (UGV). Then, it determines the sequence of target allocation to minimize the task time and to minimize the accumulated distance each drone travels. The limited payload capacity of each drone and the need to refill stock carried by the UGV are also considered. After allocating the targets, a safe trajectory is generated for each drone to avoid collision with other drones, considering uncertainty in the drones’ positions. When a drone reaches a target, the system allocates a new target, and the cycle repeats until the task is completed. The system is reactive to the evolution of the task and adjusts accordingly. An additional tested factor is the impact of the positioning error on the task time. The system was evaluated through dynamic simulations using real datasets of peach and pear orchards and finally in a laboratory proof-of-concept experiment using a micro-drone system.

Phosphorus Fertilization Can Improve Young Almond Tree Growth in Multiple Replant Settings

Young almond (Prunus amygdalus) orchards replanted where old orchards of stone fruits (Prunus sp.) have been removed are subject to physical, chemical, and biotic stressors. Among biotic challenges, for example, is almond/stone fruit replant disease (ARD; formally known as Prunus replant disease), which specifically suppresses the growth and yields of successive almond and other stone fruit plantings and is caused, in part, by a soil microbial complex. During four orchard trials representing different almond replant practices and scenarios in the San Joaquin Valley in California, we examined the impacts of phosphorus (P) fertilization on the growth of replanted almond. During all trials, P was applied to tree root zones just after replanting, and the impact was assessed according to trunk cross-sectional area (TCSA) growth for 2 years. Expt. 1 was performed where a previous almond orchard was cleared using whole orchard recycling (i.e., the old orchard was “chipped” and then turned into the soil). The land was replanted without preplant soil fumigation. We tested separate fertilizer treatments based on various P, nitrogen, micronutrient, and “complete” formulations. Expt. 2 was also performed where an old almond orchard was recycled, but the soil was preplant-fumigated before replanting. Here, we tested only P fertilization. Expts. 3 and 4 were conducted where an old peach (Prunus persica) orchard was removed. Here, P and nitrogen fertilizer treatments were tested among additional factors, including preplant soil fumigation (Expts. 3, 4) and whole orchard recycling chips (Expt. 4). During all four trials, P fertilization (P at 2.2 to 2.6 oz/tree within a few weeks after planting) significantly increased TCSA growth. The growth benefit was nuanced, however, by almond cultivar, date of replanting, rootstock, and other site-specific factors. Although P fertilization did not match the benefit of preplant soil fumigation for the management of ARD, our data indicated that P fertilization can improve the growth of young almond orchards in diverse replant settings with or without preplant soil fumigation and should be considered by California almond producers as a general best management practice.

A metapopulation framework integrating landscape heterogeneity to model an airborne plant pathogen: The case of brown rot of peach in France

Plant disease dynamics are driven by the concurrent interplay of host susceptibility, pathogen presence, and environmental conditions. While host susceptibility and environmental conditions can readily be characterized, the transmission of an airborne pathogen depends on the biotic and abiotic conditions of the surrounding environment. We propose an original metapopulation framework integrating landscape heterogeneity, in terms of climate and host density, where populations of plant hosts are connected via air-masses which allow pathogen dispersal. We explicitly account for climatic drivers affecting pathogen transport while modelling aerial dispersal using Lagrangian simulations, as well as host phenology and infection. We calibrate the model parameters according to the literature and using Approximate Bayesian Computation against observations of brown rot incidence in French peach orchards from 2001 to 2020 across an area of 50,000 km2. We use the model to produce maps of risk, distinguishing site dangerousness (risk of causing secondary infection in other sites) and vulnerability (risk of becoming infected) across the our study area. We demonstrate that airborne transport of Monilinia spores is essential in describing the spread of brown rot in French orchards in the considered period. We find that most dangerous and vulnerable sites are located along the Rhône Valley, due to the concurrence of high density of peach cultivation, a suitable climate and persistent airborne connections. Our work represents a first step to integrate metapopulation theory, epidemiology and air-mass movements to inform plant protection strategies at the national level. Furthermore, it could be adapted to optimize crop protection under future climate projections.

Navigation system for orchard spraying robot based on 3D LiDAR SLAM with NDT_ICP point cloud registration

Autonomous navigation of orchard spraying robots can effectively improve operational efficiency and reduce workload. The conventional robot navigation solutions based on the Global Navigation Satellite System (GNSS) are susceptible to signal loss in orchards due to interference from the canopy of fruit trees. In this paper, an autonomous navigation scheme for orchard spraying robots based on multi-sensor devices and the three-dimensional (3D) LiDAR Simultaneous Localization and Mapping (SLAM) technology. The initial step of the scheme involved the construction of a 3D point cloud map of the orchard using the 3D LiDAR SLAM algorithm. Subsequently, a designed point cloud map transformation algorithm was used to convert the 3D point cloud map of the orchard into a two-dimensional (2D) grid map containing key feature information of the orchard. To enhance the mapping accuracy of the orchard point cloud, a point cloud registration algorithm combining Iterative Closet Point (ICP) and Normal Distributions Transform (NDT) was proposed. This algorithm initially utilized the NDT algorithm for coarse point cloud registration to obtain transformation parameters. Then, the ICP algorithm was applied in conjunction with the obtained parameters for fine registration. Regarding obstacle avoidance, a cooperative obstacle avoidance algorithm based on the Robot Operating System (ROS) multithreaded communication mechanism was introduced. Experimental trials conducted in a standardized spindle-shaped peach orchard validated the successful completion of the SLAM mapping trajectory, which was achieved through the utilization of the proposed NDT_ICP point cloud registration algorithm. The average absolute pose error between the mapped trajectory and the reference trajectory was 1.173 m, with a standard deviation of 0.498 m. The robot's positioning and navigation errors increased with higher speeds, with the largest positioning deviation observed at 1.2 m/s speed, with a maximum lateral positioning error of 7.04 cm. The robot's average lateral navigation error did not exceed 16 cm, and the average heading deviation was less than 8° at different speeds of 0.4, 0.8 and 1.2 m/s. Both the positioning and navigation accuracies of the robot were sufficient to meet the autonomous operational requirements of orchard spraying robots.