Citrus Growers Research Articles

Citrus growers' knowledge, attitudes, and implementation towards Good Agricultural Practices (GAPs) in Palpa, Nepal

There is a high demand of citrus fruits in mid-hills region of Nepal. To increase its productivity, it is important to incorporate sustainable practices into orchard management. Therefore, the study was conducted in summer 2022 to understand commercial citrus farmers' knowledge on Good Agricultural Practices (GAPs) and correspond production methods of GAP aware farmers with GAP standards in the Palpa, Nepal. Altogether, 64 commercial citrus growers were interviewed with pre-tested semi-structured questionnaires for the data collection. The farmers were categorized into GAP aware and unaware based on the criteria made by the group discussion with the leading farmers and GAP standards. The result revealed that out of ten selected standards, adoption of GAP standards by GAP aware farmers are positive in relation to orchard management practices (99%), plantation (90%), harvest and storage (90%), soil management and fertilization (63%), and hygiene and environment management (61%)— with human welfare (100%) adopted by all of the aware respondents and GAP related to documentation and records (25%) were found to be least adopted. The entire aware respondents agreed to the fact that GAP produced fruit have a better appearance and improved quality, satisfies national and international standards and enhances the export potential of fruits but 97% of respondents didn’t agree that adopting GAP helps in providing incentives or support from governmental organizations. The understanding of GAP among the citrus growers is limited and hence, it is crucial to organize awareness programs and provide supplementary training sessions to enhance their understanding and adoption of GAP practices.

Impact of the degree of agricultural green production technology adoption on income: evidence from Sichuan citrus growers

Enhancing farmers’ adoption of agricultural green production technology (AGPT) is crucial for the green transformation of the agricultural sector. Obtaining additional income is the primary motivation for farmers to adopt AGPTs. Therefore, clarifying the relationship between AGPTs’ adoption degree and income will facilitate the possibility of farmers’ adoption of AGPTs. Based on research data obtained from 805 citrus farmers in Sichuan Province, this study examines the impact of the degree of AGPT adoption on farmers’ income and its mechanisms using the inverse probability weighted regression adjustment (IPWRA) model. These findings indicate: (1) The greater the degree of adoption of AGPTs by farmers, the more pronounced the impact on income increase. Using 1, 2, and 3 AGTs can increase farmers’ income from citrus sales by 7.1, 10.5, and 19.8 percentage points, respectively. (2) The adoption of AGPTs leads to increased income through higher yields and sales prices, which offset the incurred costs. (3) Market channels and farmers’ operating scales can affect the revenue effect of AGPT adoption. (4) Factors (i.e., education level, physical health status, and cultivation area) can affect farmers’ adoption of AGPTs. This study presents policy recommendations based on the above conclusions, aiming to guide the government in promoting AGPTs and advancing agricultural green transformation.

Optimal management of citrus disease and extreme climatic factors

This study develops a dynamic bioeconomic model using the Bellman equation to derive the optimal management strategy for Witches’ Broom Disease of Lime (WBDL) and the optimal replanting age of citrus trees after the first attack under multiple scenarios of disease management options and climate conditions. In addition, the study investigates different scenarios of disease presence and spread given different climatic conditions of arid, semi-arid and tropical zones in Oman. Factors such as disease incidence, severity, spread, and specific climatic conditions of three growing regions are considered. The farmers' optimal disease mitigation decision is determined by the disease density and insect vector level on the farm, and adverse climate conditions have a significant negative impact on the economic value of citrus cultivation. Results indicate that management measures by citrus growers and policymakers should be based on the climatic conditions of the growing region with a high level of treatment frequency and intensity in the arid region, and lime production should be concentrated in the tropical and semi-arid regions of the country.

Integrated pest management adoption among citrus growers in Iran: an application of the protection motivation theory.

Integrated pest management (IPM) is recognized as a sustainable approach to pest control. However, adoption rates among farmers in Iran have been observed to be low. This study investigates the adoption of IPM practices among citrus farmers in Iran and assesses the applicability of the protection motivation theory (PMT) in explaining farmers' behavior towards IPM. Overall, farmers reported poor levels of IPM use, paying attention only to monitoring practices among the three groups of IPM practices examined (prevention, monitoring, and suppression). The perceived severity of the consequences of chemical pest control (β = 0.389, P < 0.001), the response efficacy of IPM practices (β = 0.254, P < 0.001), and the perceived self-efficacy of using IPM practices (β = 0.199, P < 0.001) positively predicted adoption of IPM practices, while response cost/barriers of IPM practices (β = -0.355, P < 0.001) negatively predicted adoption of IPM practices. The PMT model presents a unique and interesting perspective to understand if and how IPM practices against the threat of pests are motivated. The perceived severity of the consequences of chemical pest control showed the strongest positive effect, whereas the response cost/barriers of IPM practices showed the strongest negative effect on IPM adoption. © 2024 Society of Chemical Industry.

Morphogenetic characterization of Xanthomonas citri pv. citri and its management

BackgroundPakistan’s economy largely depends on citrus cultivation, and citrus fruits generate significant foreign exchange. Xanthomonas citri pv. citri (Xcc) is the primary cause of citrus canker (CC), which poses a significant threat to the industry. The management of disease is made more difficult by the lack of resistant variants against different Xcc races. Understanding and addressing Xcc are critical for maintaining the industry given the economic reliance on citrus. MethodsIn order to isolate Xcc in a lab, a thorough survey was conducted in the districts of Bahawalpur, Multan, and Dera Ghazi Khan to collect samples showing canker symptoms. Gram-negative bacteria were identified in the isolates by biochemical analysis, and Koch’s postulates confirmed Xcc as the CC causing agent. DNA extraction and sequencing were used in the molecular characterization, which confirmed the phylogenetic relationship with Xcc. Using the disc sensitivity method, nine antibiotics were tested at 300, 500, and 700 ppm concentrations to evaluate CC management. Amoxicillin was found to be highly effective in inhibiting the growth of Xcc colonies. ResultsThe study provided morphogenetic insights and established Xcc as the causal agent of CC. All strains matched Xcc in molecular characterization, but antibiotic sensitivity testing revealed inconsistent efficacy. Amoxicillin proved to be very effective at stopping the growth of Xcc colonies at every tested dosage. ConclusionThis study makes an important contribution to our understanding of XCC and helps the citrus industry develop better disease control plans. Future interventions against citrus canker can benefit greatly from the understanding provided by morphogenetic characterization and antibiotic sensitivity profiles. The discovery of amoxicillin’s high efficacy highlights the drug’s potential for treating diseases linked to Xcc. These results help to protect citrus growing, maintaining the viability of an important industry in Pakistan’s agricultural landscape.

Physiological and biochemical characterisation of split and healthy Daisy mandarin (Citrus reticulata Burm.) fruits

ABSTRACT Fruit splitting is a prevalent physiological disorder that has a significant impact on Daisy mandarin fruit production, posing challenges to farmers in terms of productivity and economic viability. Despite its impact, no prior research on fruit splitting in Daisy mandarin has been conducted. This study aimed to assess the effect of fruit splitting on quality, morphological characteristics, biochemical composition and nutrient content in Daisy mandarin. In 2022, a comprehensive analysis was conducted on both split and healthy Daisy mandarin fruits, budded on Rough lemon rootstock, to investigate their morphological characteristics, biochemical characteristics, mineral content and cell wall components. Additionally, the study examined the activity of cell wall-degrading enzymes, such as peroxidase (POD), cellulase (Cx) and polygalacturonase (PG). The Results indicated that split fruits exhibited larger fruit size and weight and increased water content in both the fruits and peel compared to healthy fruits. However, split fruits had thinner peel thickness and lower peel content. The peels of split fruits also contained higher level of total soluble sugars, amino acids, and proline content. Furthermore, the peels of split fruits displayed much higher activity of cell wall-degrading enzymes than those of healthy fruits. The nutrient analysis of the split fruits revealed a decrease in boron, calcium and potassium content in the peel compared to healthy fruits. The study provides crucial insights into the mechanisms underlying fruit splitting, identifying biochemical and physiological differences between split and healthy fruits. These findings offer valuable information for developing strategies to mitigate fruit splitting, enhancing fruit quality and reducing economic losses for citrus growers. Future research should explore the genetic and environmental factors contributing to fruit splitting and investigate potential interventions to improve nutrient management and fruit integrity in Daisy mandarin cultivation.

“Extreme hybrids” from the Australian citrus rootstock breeding program

Citrus is one of the most genetically diverse fruit trees used by humans, and yet few rootstock breeders have ventured beyond a narrow range of parents. For the last 25 years we have explored wider graft and sexual compatibility within the citrus subfamily (Aurantioideae) than any previous attempts, and have identified new genera and species for rootstock breeding. Whilst the vast majority of this work has met with failure, it has identified factors such as sexual incompatibility, late-acting lethality and poor field adaptation as the reasons why many citrus relatives are not currently amenable to rootstock breeding. A major breakthrough early in the program was the discovery that Oceania citrus species are extremely sensitive to Citrus tristeza virus (CTV) when used as rootstocks, and the realisation that resistance must be introgressed if we are to ever discover useful traits masked by this disease sensitivity. Bridging hybrids were required to transfer this virus resistance and a newly discovered species (Citrus wakonai) was employed to speed-up the process. After three generations of crossing, our “extreme hybrids” with Oceania parentage now show commercial performance equivalent to industry standards. By providing citrus growers with a range of high-performance rootstocks from extremely complex genetic backgrounds we can increase the biological diversity of orchards without compromising production. Our hope is that these “extreme hybrids” may help in the battle against Huanglongbing (HLB) disease.

Investigating population dynamics and evaluating damage incurred by Thripidae (Thysanoptera) species in citrus orchards of Northeastern Morocco: an exemplary analysis in Berkane

Thrips are significant pest of crops, vegetables, and fruiting trees, and various species of thrips can infest citrus at fruit formation as well as new leaf sprouts. Thrips presence and damage can significantly reduce the export value of fruits, making them a major concern for citrus growers. Field studies were conducted to investigate the biodiversity and abundance of citrus thrips on an early fruiter citrus cultivar in experimental and commercial orchards of Morocco. In this study, we investigated the abundance, economic importance, dynamics, and seasonal fluctuations of citrus thrips in relation to citrus phenology. We identified four species of thrips that infest citrus orchards, including Frankliniella occidentalis, Pezothrips kellyanus, Scirtothrips sp, and Aeolothrips sp. Our results showed that the quantitative peak of thrips occurred during the blooming stage, and that the number of thrips caught on sticky traps during bloom could be a suitable predictive method for estimating final fruit damage. The population dynamics of thrips species were found to depend on several biotic and abiotic factors, including temperature, rainfall, and chemical interventions. We also observed that some citrus varieties were more susceptible to thrips attacks than others, with Washington navel and Maroc late being the most infested orchards with infestation rates of 32% and 24%, respectively. Our findings provide important insights into the abundance, economic importance, and seasonal fluctuations of citrus thrips, which can inform the development of effective control strategies to mitigate their damage in citrus orchards.

Water Use Efficiency in a Deficit-Irrigated Orange Orchard

Citrus is a subtropical fruit tree with high water requirements. This study aimed to determine the effects of water deficit on an orange orchard subjected to different water-saving strategies. The study was realised in an orange orchard in a semiarid area by adopting four different water management techniques: 100% crop evapotranspiration (control); SSDI—subsurface sustained deficit irrigation; RDI—regulated deficit irrigation; PRD—partial rootzone drying treatment during five growing seasons. The experimental design foresaw a randomised block design with six replicates per treatment (24 index plants). The results of the study showed that the water-saving strategies reduced irrigation water consumption by 25% (SSDI), 33% (RDI), and 49% (PRD) compared to the fully irrigated treatment without yield reduction, thus increasing water use efficiency. Mineral nutrition of the trees was slightly affected by irrigation treatments; element concentration in leaves was generally in the optimal range; only potassium showed values below the recommended leaf concentrations. Regarding fruit quality parameters, the vitamin C concentration in RDI showed significant differences with a value of 62.7 mg 100 mL−1 compared to 58.5 mg 100 mL−1 in the control. Plants subjected to SSDI and PRD strategies showed increased levels of pulp colour index with significant values of 10 and 9.90, respectively, compared to the control (8.44). By implementing targeted water management, citrus growers could save water and increase the ascorbic acid and sugar concentration in the fruits; anthocyanins also increased but not significantly. These findings open new market opportunities for citrus growers in marginal areas, where they cannot rely solely on producing citrus fruits to remain competitive.

Resistance of Phyllocoptruta oleivora (Acari: Eriophyidae) to acaricides in Turkey

Phyllocoptruta oleivora (Ashmead) (Acari: Eriophyidae) is a significant pest. The use of pesticides is the main strategy for its control and it has increased year by year. However, citrus growers stated that the effects of the acaricides have decreased in recent years. In order to determine whether this is due to resistance, P. oleivora populations were collected from Erdemli (Mersin), Karataş, Kozan, Yüreğir (Adana), and Balcalı (as a susceptible) in Turkey. Adults were bioassayed with abamectin, sulfur, spirodiclofen, and pyridaben, which are widely used and have different modes of action. Based on the bioassay experiments, the most resistant population to abamectin was found to be that from Kozan with 25.31-fold, and the population with the lowest resistance was determined to be that from Yüreğir with 8.13-fold both compared to susceptible population. All populations showed low resistance against sulfur, the highest resistance ratio to sulfur was found in Yüreğir with 2.53-fold. The highest resistance population against spirodiclofen was detected in Erdemli with 24.00-fold, followed by Karataş, Yüreğir, and Kozan populations with 15.39, 14.05, and 9.21-fold, respectively. The resistance ratios of P. oleivora populations against pyridaben were found to be 30.30, 15.85, 10.10, and 7.55-fold in Erdemli, Kozan, Yüreğir, and Karataş, respectively. The detected status of acaricide resistance indicates that this phenomenon takes place and should be a concern in the Eastern Mediterranean Region of Turkish populations of P. oleivora requiring monitoring and planning of resistance management strategies. The use of acaricides with different modes of action in sequential spraying is essential to prevent the development of resistance.

Economic and Social Impact of Huanglongbing on the Mexico Citrus Industry: A Review and Future Perspectives

The citrus industry is of great importance in Mexico, with an estimated production value of USD 2.4 billion and the potential to generate up to 28 million employees per year. Approximately 69,000 Mexican families depend on this sector. However, it is under serious threat from the disease known as Huanglongbing (HLB). The rapid spread of this disease has caused significant economic losses, impacted the livelihoods of citrus growers, and led to substantial job losses. Currently, HLB is not under control in Mexico, and as the management strategies applied have proven to be ineffective, yields have not been recovered to pre-HLB levels, and production costs have significantly increased. Therefore, it remains the most destructive citrus disease. This review paper describes the current situation of the disease, its economic and social impact, and the measures adopted for its management in Mexico. Future perspectives highlight advances in research based on new biotechnological tools as an eco-friendly management alternative. Practical suggestions to address HLB are also mentioned in our analysis.

Citrus nutrition research in northeast India: An overview

History of citrus growing in northeast India is as old as the tradition of citrus as its natural home of citrus hots-spots. Unfortunately, citrus of late is being tagged highly uncomfortable in its natural homeyard in northeast India, with some exceptions in Garo hills of Meghalaya and Pasighat of Arunachal Pradesh. Multiple nutrient deficiencies backed up by staggering nutrient mining have made citrus suffer from both production as well as quality issues, besides other issues of early onset of citrus decline and reduced post -harvest shelf life. Such depleted production incentives have put citrus growing on back-foot. Distinct absence of nutrient diagnostics coupled with lack of balanced fertilization have further hiked the miseries of citrus growers in the region. Citrus -based Soil health Card is another missing link putting citrus growers always managing their citrus orchards with complete guess-work, a complete sorry-state-of-affair, unless something too early and too quickly is done in this direction before it becomes too late and too little. Research need a complete reorientation in their objectivity of citrus nutrition with an eye on organic citrus integrating agroecological considerations using strictly adopted on-farm citrus module coupled with contingency irrigation planning by holding surplus rainwater.

Molecular based associations of bacterial pathogens with citrus: Implications for toxicology and disease management

The losses associated with the bacterial diseases of citrus leaves and fruits have been reported throughout all of Pakistan's citrus-growing regions and a lot of work was done on the morphological characterization of pre and post-harvest pathogens. However, this issue has not been addressed in Khanpur, which is a major citrus-producing city in Pakistan and can help in the economic growth of the country. The citrus fruits in the area under study exhibit disease symptoms during pre and post-harvesting, but the actual disease agents have not yet been identified. The retrospective object of the current research is to study the pathogenic variation along with the investigation of bacterial disease incidence i.e. citrus canker, bacterial spots, & HLB in citrus fruit. During a survey conducted in November 2019 and 2020, bacterial isolates from symptomatic citrus fruits were obtained from randomly chosen orchards in Khanpur.The disease assessment was estimated by determining prevalence, severity, and disease incidence (DI). The bacterial isolates were identified morphologically and further through 16S rRNA gene amplification. The identified species were Pseudomonas syringae, Pseudomonas viridiflava, Serratia marcescens, Xanthomonas axonopodis pv citri, and Candidatus liberibacter. In the pathogenicity test, the Xanthomonas strains responsible for the canker disease caused the most severe disease symptoms. To our knowledge, this is the first report on pathogens of citrus fruits in Khanpur. Given the significant contribution of citrus fruits to household income and foreign exchange in Pakistan, this study illustrates the molecular-based association of bacterial pathogens of citrus and the toxic behavior of pathogens which helps to provide recommendations on genetic testing and to develop management programs for disease management. The molecular identification of citrus pathogens will empower the citrus growers, researchers, and regulatory agencies to make informed decisions that will protect citrus crops, reduce economic losses, and promote sustainable agriculture. It is also likely to play an increasingly vital role in the future of citrus cultivation..

Occurrence and Multiplex PCR Detection of Citrus Yellow Vein Clearing Virus in Korea.

Citrus yellow vein clearing virus (CYVCV) is a member of the Alphaflexiviridae family that causes yellow vein clearing symptoms on citrus leaves. A total of 118 leaf samples from nine regions of six provinces in Korea were collected from various citrus species in 2020 and 2021. Viral diagnosis using next-generation sequencing and reverse transcription polymerase chain reaction (RT-PCR) identified four viruses: citrus tristeza virus, citrus leaf blotch virus, citrus vein enation virus, and CYVCV. A CYVCV incidence of 9.3% was observed in six host plants, including calamansi, kumquat, Persian lime, and Eureka lemon. Among the citrus infected by CYVCV, only three samples showed a single infection; the other showed a mixed infection with other viruses. Eureka lemon and Persian lime exhibited yellow vein clearing, leaf distortion, and water-soak symptom underside of the leaves, while the other hosts showed only yellowing symptoms on the leaves. The complete genome sequences were obtained from five CYVCV isolates. Comparison of the isolates reported from the different geographical regions and hosts revealed the high sequence identity (95.2% to 98.8%). Phylogenetic analysis indicated that all the five isolates from Korea were clustered into same clade but were not distinctly apart from isolates from China, Pakistan, India, and Türkiye. To develop an efficient diagnosis system for the four viruses, a simultaneous detection method was constructed using multiplex RT-PCR. Sensitivity evaluation, simplex RT-PCR, and stability testing were conducted to verify the multiplex RT-PCR system developed in this study. This information will be useful for developing effective disease management strategies for citrus growers in Korea.

Development of an automated needle-based trunk injection system for HLB-affected citrus trees

Trunk injection of chemical compounds is a target-specific method of applying therapeutics that increases applied compound efficiency without compromising environmental safety and has proven to be an effective method to control citrus Huanglongbing (HLB). However, conventional (manual) trunk injection methods are labour-intensive and time-consuming, resulting in high application costs and posing implementation challenges for commercial citrus growers. For this reason, an automated, drill-free system for injecting therapeutic materials into citrus trees to control HLB has been developed. The injection mechanism consists of an end effector and a retractable telescoping positioning arm mountable to a farm vehicle. The system employs a metering pump with adjustable maximum pressure and flow rate for injecting therapeutic materials into tree trunks. This novel technology was evaluated in commercial citrus orchards; the applied volume, injection rate, and injection pressure were measured, and differences based on the time of injection, trunk diameter at the injection point, and irrigation status were examined. The injection was performed until the flow stopped; the injection duration ranged from 30 s to 72 s for all trees. The minimum and maximum volume injected was 53.9 mL and 243.6 mL, respectively, at 44 s and 68 s. The average injection rate per tree ranged from 1.23 mL s−1 to 3.58 mL s−1, and cut-off pressure ranged from 0.97 MPa to 2.01 MPa.

Climate changes altered the citrus fruit quality: A 9-year case study in China

Global climate change has significantly impacted the production of various crops, particularly long-term fruit-bearing plants such as citrus. This study analyzed the fruit quality of 12 citrus orchards (Citrus Sinensis L.Osbeck cv. Bingtang) in a subtropical region in Yunnan, China from 2014 to 2022. The results indicated that high rainfall (>220 mm) and low cumulative temperature (<3150 °C) promoted increases in titratable acidity (>1.8 %) in young fruits. As the fruits further expanded (with a horizontal diameter increasing from 50 to 65 mm), excessive rainfall (300-400 mm), lower cumulative temperature (<2400 °C), and a reduced diurnal temperature range (<10 °C) hindered decreases in titratable acidity. Conversely, low rainfall (<220 mm), high cumulative temperature (>3150 °C), and a high diurnal temperature range (>14 °C) promoted the accumulation of soluble solids in young fruits (9 %) at 120 days after flowering (DAF). Furthermore, low rainfall (<100 mm) favored the accumulation of soluble solids (1.5 %) during fruit expansion (195-225DAF). To quantify the relationship between fruit acidity and climate variables at 120 DAF, we developed a regression model, which was further validated by actual measurements and accurately predicted fruit acidity in 2023. Our findings have the potential to assist citrus growers in optimizing cultivation techniques for the production of high-quality citrus under increasingly variable climatic conditions.

The spread of the intensive agricultural model by agro-suppliers in Algeria: implications for citrus small family farms and their adaptations

This study aims to investigate how small family farms, lacking direct support from advisory services, cope with challenges including access constraints to resources, and enhance their resilience. Investigations conducted in the wilaya of Blida, Algeria, through surveys of 17 input suppliers and citrus growers, revealed how the institutional context, particularly that of private agricultural 241 advisory, incentivizes farms to adopt hyper-intensive agriculture by using more agro-chemicals. Indeed, the arrival of input suppliers into the agricultural advisory landscape has resulted in socio-economic differentiation between farms, with small and most vulnerable farms resisting these intensive models. The results show that even if these small farms face difficulties in existing in the face of the big ones supported by the institutional environment, particularly the private sector, resilience factors have been identified that enable these farms to resist to the steamroller of the intensive model: solidarity between small family farms, pluriactivity, and taking advantage of some state support measures and the public-private partnership of farm advisory services.

Factors affecting awareness on good agriculture practices among citrus growers in Palpa, Nepal: Through binary logistic regression approach

Being an indigenous high-value commodity, with significant market demand in the mid-hills of Nepal, citrus requires the incorporation of sustainable techniques in orchard to increase fruit production. For farmers in Nepal, Good Agricultural Practices (GAP) is a novel concept. The majority of farmers are unaware of it, and those who are aware also have not fully embraced the techniques. Therefore, the study was conducted in summer 2022 to assess the factors that affect the awareness of GAP among the farmers at Palpa, Nepal. Rainadevi Chahara and Ribdikot rural municipality of Palpa district, Nepal was purposively selected, and altogether, 64 commercial citrus growers from the municipalities were taken by simple random sampling technique. The binary logistic regression model was used for analyzing the effect of different variables on the awareness of GAP among citrus growers. Different demographic and socioeconomic variables have been found associated for odds of being GAP aware. The findings revealed that, farmers’ who are GAP aware have an access to trainings and contact with extension agents, 4.164 and 10.293 times higher than those farmers who are GAP unaware respectively. Therefore, the study suggests that farmers knowledge on GAP can be further expanded through trainings and frequent contact with extension agents as they are the major factors affecting commercial citrus growers’ awareness to GAP in Palpa district, Nepal.

Extracting Citrus-Growing Regions by Multiscale UNet Using Sentinel-2 Satellite Imagery

Citrus is an important commercial crop in many areas. The management and planning of citrus growing can be supported by timely and efficient monitoring of citrus-growing regions. Their complex planting structure and the weather are likely to cause problems for extracting citrus-growing regions from remote sensing images. To accurately extract citrus-growing regions, deep learning is employed, because it has a strong feature representation ability and can obtain rich semantic information. A novel model for extracting citrus-growing regions by UNet that incorporates an image pyramid structure is proposed on the basis of the Sentinel-2 satellite imagery. A pyramid-structured encoder, a decoder, and multiscale skip connections are the three main components of the model. Additionally, atrous spatial pyramid pooling is used to prevent information loss and improve the ability to learn spatial features. The experimental results show that the proposed model has the best performance, with the precision, the intersection over union, the recall, and the F1-score reaching 88.96%, 73.22%, 80.55%, and 84.54%, respectively. The extracted citrus-growing regions have regular boundaries and complete parcels. Furthermore, the proposed model has greater overall accuracy, kappa, producer accuracy, and user accuracy than the object-oriented random forest algorithm that is widely applied in various fields. Overall, the proposed method shows a better generalization ability, higher robustness, greater accuracy, and less fragmented extraction results. This research can support the rapid and accurate mapping of large-scale citrus-growing regions.

Climate zoning: identifying suitable regions for the occurrence of Alternaria Brown spot in tangerine trees in Brazil.

Brazilian citrus farming has been migrating to nontraditional citrus-growing regions, which can be considered a challenge for citrus growers, as not all these areas are suitable for tangerine cultivation. Thus, the mapping of regions exhibiting favorable climatic conditions for Alternaria brown spot has become crucial in the selection of appropriate locations for the establishment of new orchards. This mapping enables the implementation of an avoidance strategy, which entails steering clear of areas where the disease is prevalent, aligning with fundamental principles of disease control. Thus, this study seeks to zone areas with high and low climatic favorability for the occurrence of Alternaria brown spot in tangerine trees in Brazil. Historical climate data series from the NASA-POWER database were used for all municipalities in Brazil. Agrometeorological variables used to determine the development of Alternaria brown spot were average monthly air temperature (Tmean) and duration of leaf wetness period (LWD). Areas were considered unsuitable climatically when Tmean was <17 °C or >33 °C, relatively suitable when Tmean was between 13 °C and 33 °C and LWD <10%, and climatically suitable when Tmean was between 13 °C and 33 °C and LWD >10%. The states of Paraná, Santa Catarina and Rio Grande do Sul showed greater thermal amplitude within months and throughout the year. The southern region of the country has harsher winters, with minimum temperatures below 15 °C, which is unfavorable for the disease incidence. The states with the greatest favorability for Alternaria brown spot were Paraná, Santa Catarina, and Rio Grande do Sul, mainly from May to September. Rio Grande do Sul was the state in this region that showed the greatest favorability, as a consequence of leaf wetness exceeding 10 h. The main tangerine-producing regions in Brazil, including the southern part of Minas Gerais, the state of São Paulo and the metropolitan region of Porto Alegre, were mostly classified as relatively favorable areas for the occurrence of Alternaria brown spot. It is recommended that when establishing new tangerine orchards, regions with lower favorability for the occurrence of Alternaria brown spot, such as the North and Central-West regions of Brazil, particularly the states of Amazonas, Pará and Mato Grosso, should be selected. © 2023 Society of Chemical Industry.