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Huanglongbing is a severe citrus disease that causes significant tree and crop losses worldwide. It is caused by three Candidatus liberibacter species and spread by psyllids and infected budwood. Various methods have been used to diagnose and understand HLB, including recent advances in molecular and biochemical assays that explore the pathogen's mode of action and its impact on the host plant. Characterization is essential for developing sustainable HLB management strategies. Nanotechnology, particularly nano sensors and metal nanoparticles, shows potential for precise disease diagnosis and control. Additionally, antibiotics, nanomaterials, and genetic engineering techniques like transgenesis offer promising avenues for mitigating HLB. These diverse approaches, from conventional to cutting-edge, contribute to developing integrated HLB management strategies for sustainable citrus cultivation. The review highlights the significant advancements in conventional and advanced molecular and biochemical characterization of HLB, aiding in early detection and understanding of the infection mechanism. It emphasizes the multidimensional efforts required to characterize disease and devise innovative management strategies. As the citrus industry faces unprecedented challenges, exploring new frontiers in HLB research provides hope for sustainable solutions and a resilient future for global citrus cultivation., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is an important insect pest of the citrus crop worldwide. It vectors the pathogen 'Candidatus Liberibacter asiaticus' (CLas) that causes a serious disease known as citrus greening. Here, we tested the infection frequency of Wolbachia and CLas from 100 D. citri individuals collected from two host plants belonging to families Rutaceae (Citrus reticulata Blanco) and Boraginaceae (Cordia myxa L.) using molecular methods. The following trend of endosymbionts infection in adult D. citri was found; 85.4% (35/41) by Wolbachia, and 19.5% (8/41) by CLas collected from C. reticulata plants and 65.4% (17/26) by Wolbachia, and 15.4% (4/26) by CLas in case of C. myxa plant. However, 61.5% (8/13) nymphs collected from C. reticulata and 20.0% (4/20) collected from C. myxa plants were infected by Wolbachia, while no nymph was infected by CLas collected from either host plants. Findings from this work represent the first report of CLas presence in D. citri feeding on C. myxa plants. By studying the presence of CLas with other endosymbiotic bacteria, future basic and applied research to develop control strategies can be prioritized., (© The Author(s) 2020. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Feeding damage by arthropods exposes plants to pathogens and interferes with plant physiological processes. Feeding by the citrus leafminer (CLM), Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), larva exposes leaf cuticle to the causal pathogens of the citrus canker disease. We investigated the impact of larval feeding on photosynthetic rate (Pn), CO2 exchange rate (Ci), and H2O exchange rate (Wi) in eight citrus cultivars [Citrus mandarins (Kinnow, Seedless Kinnow, Feutrell's early), Citrus sinensis (Succari, Salustiana), Citrus tangerines (Fairchild), Citrus limon (China lemon), and Citrus paradisi Macfad (Grapefruit)] under natural conditions in comparison with control plants protected from larval feeding. The effects on gas exchange parameters were tested by allowing the single first instar larvae per leaf to feed till pupation at the rate of three leaves per plant and 10 plants per cultivar. A consistent reduction in leaf Pn, Ci, and Wi rates with larval development through 19 d was observed in all cultivars except Grapefruit in which all three parameters decreased through 13 d and then increased consistently through 19 d. Reductions in Pn, Ci, and Wi were significantly correlated. All three parameters of CLM-infested plants were reduced significantly compared to their levels in control plants except Pn in Kinnow, China lemon, and Grapefruit; Ci in Grapefruit; and Wi in Succari. Pn was reduced most in Fairchild, whereas Ci and Wi were reduced most in China lemon. The consequences of these physiological alterations in regions with high CLM populations could be even more intense and negatively impact plant health, tolerance to pests and diseases, and yield.

Citrus is one of the major fruit crops worldwide due to its contribution to food security. Citrus orchards serve as a habitat for arthropods plethora including beneficial and harmful arthropods. Extensive field surveys were conducted to assess the diversity and abundance of arthropods from citrus plantations at six tehsils (Kotmomin, Bhalwal, Silanwali, Shahpur, Sahiwal, and Sargodha) of district Sargodha. Different traps were installed for the collection of arthropods i.e., pitfall, yellow pan, yellow sticky cards, and soil sampling. The traps were visited after every two weeks for the collection of arthropods for two consecutive years. The relative abundance of Pseudococcidae was higher (0.35%) followed by Scarabaeidae (0.14%), Carabidae (0.07%), and Chrysomelidae (0.07%) in pitfall traps. In the case of the yellow pan, the abundance of Nitidulidae (0.27%), Psyllidae (0.17%), Tetranychidae (0.23%), and Aphididae (0.09%) was higher compared to other families. Similarly, Psyllidae (0.60%), Aleyrodidae (0.25%), and Aphididae (0.24%) families of arthropods were abundant when yellow sticky cards were used. While from the soil samples, more individuals from Isotomidae (0.41%), Oribatulidae (0.39%), and Hypogastruridae (0.27%) families were collected. Based on the extensive surveys, a total of 50,966.5 citrus-associated arthropods were collected during 2018-2019, among which 20,873 were Coleopterans belonging to 7 different families. Our findings provide the baseline information for the development of Integrated Pest Management (IPM) measures against insect pests in citrus orchards to increase our citrus production. [ABSTRACT FROM AUTHOR]

Citrus crop is attacked by one of the major insect pests known as citrus leaf miner (CLM), Phyllocnistis citrella stainton that caused extensive damage in both nurseries and orchards in Pakistan. Population density of P. citrella was monitored in Citrus reticulata (Blanco orchards for 2 years by scouting weekly for larval-induced mines on the leaf surface. Current study was conducted at Department of Entomology, University of Sargodha during 2014 and 2015 to check seasonal abudance of Phyllocnistis citrella (Lepidoptera: Gracillariidae) on mandarin (Spindales: Rutaceae) Groves in Pakistan. The results showed that there was no significant difference of P. Citrella incidence in different tehsils of Sargodha. The significantly higher population of P. citrella was observed in September during both study years. While in January to March the P. Citrella populations were observed minimum. The overall, density of P. citrella was greater during 2015 (65%) compared to 2014 (61%). The abiotic factors such as temperature showed significantly positive correlation with an infestation of P. citrella, however, humidity did not show any significant effect on P. citrella infestation during both years. As seen from the results, the P. citrella infestation was more pronounced in September during both years. [ABSTRACT FROM AUTHOR]

Plant growth regulators (Kinetin, GA3 and Wokozim) and fertilizers (nitrogen, phosphorus, potassiumand calcium) alone and in various combinations were applied to young 'Kinnow' mandarin trees to improve their quality. Fruit harvested at commercial maturity was analyzed at harvest and seven days after storage at ambient conditions. Results revealed that higher seed number (20) was recorded with Kinetin at 60 mg l−1 and minimum seed number (10) with Kinetin at 30 mg l−1+ GA3 at 10 mg l−1. More healthy and less aborted seeds were recorded with Wokozim (1500 g tree−1)+2 ml l−1 foliar spray. High juice mass (%) and low rag mass (%) were observed with control and 250 g tree−1 phosphorous (P) application as single super phosphate. The TSS were higher with 150 g tree−1 calcium (Ca) applied as calcium ammonium nitrate and lower with P application at 500 g tree−1. Titratable acidity was higher in fruit treated with Kinetin at 60 mg l−1 and lower in fruit treated with NPK (230 + 250 + 250 g tree−1)+Ca (150 g tree−1)+Kinetin at 30 mg l−1. The TSS:TA ratio was higher in fruit treated with NPK (230 + 250 + 250 g tree−1)+ Ca (150 g tree−1)+Kinetin at 30 mg l−1 and lower in fruit treated with P (250 g tree−1)+ Kinetin at 30 mg l−1. Ascorbic acid was higher in fruit treated with Ca (150 g tree−1)+P (250 g tree−1)+Kinetin at 30 mg l−1 and lower with Wokozim (1500 g tree−1)+2 ml l−1 foliar applications. [ABSTRACT FROM AUTHOR]

Plants and insects are members of diverse ecological communities. Feeding of herbivore insects may damage the host plants indirectly by altering the photosynthetic activity. The objective of this study was to evaluate the physiological changes in citrus plants due to citrus leafminer (CLM) Phyllocnistis citrella Stainton (Gracillariidae: Lepidoptera) larval feeding under field condition. Plants from four economically important citrus cultivars, Citrus reticulata (Kinnow and seedless Kinnow), Citrus tangerines (Fairchild), and Citrus paradisi Macfad (Grapefruit), were selected randomly and leaf damage was assessed through an image analysis technique. The results showed that percent leaf damage was higher at 44.2% on Fairchild compared to other cultivars at 19th day of post-feeding. The reduction in leaf photosynthesis (Pn), stomatal conductance (C), and transpiration rate (E) rates due to larval feeding through 19th day was found consistent in all cultivars except Grapefruit. After 13 days, Pn and gaseous exchange rates in damaged leaves of Grapefruit recovered to some extent but remained significantly lower than in control through 19th day. Reduction in all three physiological parameters in infested leaves was ranged as Fairchild > Kinnow > seedless Kinnow > Grapefruit compared to their level in control. Percent of leaf damage had a strong and negative relation with Pn, C, and E in all citrus cultivars except Grapefruit in which all variables showed a weak relation. Conclusively, P. citrella may cause a serious threat to citrus plants even at lower levels of infestation, and these physiological impairments could be more intense in regions with high P. citrella population. [ABSTRACT FROM AUTHOR]

Citrus leafminer (CLM), Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) is among the serious insect pests attacking citrus plants in Pakistan. The study was conducted to quantify the leaf area damage of eight citrus cultivars caused by mining activity of CLM during summer 2016. The total leaf area and mine area per leaf were calculated by the image analysis method using Sigma Scan Pro 5.0 software. The results of the present study showed that CLM generated larger mines; 1.64 cm2 on Grapefruit, 1.44 cm2 on Kinnow and 1.40 cm2 on Succari compared to other five cultivars. However, the percent leaf damage due to the feeding of CLM larvae was observed higher 44.2% on Fairchild, 36.5% on seedless Kinnow, 36.3% on Feutrell's early and 35.8% on Kinnow that showed great susceptibility to CLM. Smallest mines generated by CLM larvae were found on China Lemon and Succari showing the lowest damage percentage compared to other cultivars. Conclusively, the C. tangerines and C. mandarins were the most preferred cultivars by CLM larvae for feeding on the leaf surface. The image analysis method was accurate, relatively simple, easy and inexpensive to calculate the leaf area damage caused by CLM larvae. [ABSTRACT FROM AUTHOR]

Citrus leafminer (CLM), Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) is a destructive insect pest of citrus nurseries as well as orchards in Pakistan. The aim of this study was to assess the effectiveness of some synthetic insecticides and essential oils against citrus leafminer larvae. Two laboratory bioassays, leaf dip bioassay (LDB) and topical bioassay (TB) were developed to check the efficacy of tested chemicals and essential oils. As seen from results, abamectin showed significant mortality (63.5%) of CLM larvae when topical bioassay was performed. Similarly, the percent mortality of CLM larvae was 53.8% after application of abamectin, when leaf dip bioassay technique was used. However, among tested botanicals, Azadirachta indica oil showed better results with percent CLM mortality of 35.6%, through topical bioassay and 31.8% through leaf dip bioassay. In the case of A. indica, the LC50 value was also observed lower (1.88±0.37, 1.73±0.29) in LDB and TB, respectively, as compared to other botanicals. So, our study suggested that abamectin gave better management of citrus leafminer larvae. However, higher concentrations of A. indica oil can be used to control CLM larvae. [ABSTRACT FROM AUTHOR]

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is a major insect pest of citrus (Citrus spp.) and some other plants related to the Rutaceae family. It is also a vector of the pathogen Candidatus Liberibacter asiaticus (CLas), the bacterium associated with a serious disease of citrus plants known as Huanglongbing. Little is known about other host plants of D. citri. We documented for the first time D. citri defoliating lasora, Cordia myxa L. (Family Boraginaceae), in the southern region of the state of Punjab, Pakistan. About eight to 10 adults and 15 to 18 nymphs were observed per shoot of the lasora plant. [ABSTRACT FROM AUTHOR]