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Littérature scientifique sur le sujet « Citrus Diseases and pests »

Auteur : Grafiati

Publié le 4 juin 2021

Mis à jour le 29 janvier 2023

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Articles de revues sur le sujet "Citrus Diseases and pests"

Lin, Yuke, Jin Xu et Ying Zhang. « Identification Method of Citrus Aurantium Diseases and Pests Based on Deep Convolutional Neural Network ». Computational Intelligence and Neuroscience 2022 (27 mai 2022) : 1–8. http://dx.doi.org/10.1155/2022/7012399.

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The traditional identification methods of Citrus aurantium diseases and pests are prone to convergence during the running process, resulting in low accuracy of identification. To this end, this study reviews the newest methods for the identification of Citrus aurantium diseases and pests based on a deep convolutional neural network (DCNN). The initial images of Citrus aurantium leaves are collected by hardware equipment and then preprocessed using the techniques of cropping, enhancement, and morphological transformation. By using the neural network to divide the disease spots of Citrus aurantium images, accurate recognition results are obtained through feature matching. The comparative experimental results show that, compared with the traditional recognition method, the recognition rate of the proposed method has increased by about 11.9%, indicating its better performance. The proposed method can overcome the interference of the external environment to a certain extent and can provide reference data for the prevention and control of Citrus aurantium diseases and pests.

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Lee, Saebom, Gyuho Choi, Hyun-Cheol Park et Chang Choi. « Automatic Classification Service System for Citrus Pest Recognition Based on Deep Learning ». Sensors 22, n^o 22 (18 novembre 2022) : 8911. http://dx.doi.org/10.3390/s22228911.

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Plant diseases are a major cause of reduction in agricultural output, which leads to severe economic losses and unstable food supply. The citrus plant is an economically important fruit crop grown and produced worldwide. However, citrus plants are easily affected by various factors, such as climate change, pests, and diseases, resulting in reduced yield and quality. Advances in computer vision in recent years have been widely used for plant disease detection and classification, providing opportunities for early disease detection, and resulting in improvements in agriculture. Particularly, the early and accurate detection of citrus diseases, which are vulnerable to pests, is very important to prevent the spread of pests and reduce crop damage. Research on citrus pest disease is ongoing, but it is difficult to apply research results to cultivation owing to a lack of datasets for research and limited types of pests. In this study, we built a dataset by self-collecting a total of 20,000 citrus pest images, including fruits and leaves, from actual cultivation sites. The constructed dataset was trained, verified, and tested using a model that had undergone five transfer learning steps. All models used in the experiment had an average accuracy of 97% or more and an average f1 score of 96% or more. We built a web application server using the EfficientNet-b0 model, which exhibited the best performance among the five learning models. The built web application tested citrus pest disease using image samples collected from websites other than the self-collected image samples and prepared data, and both samples correctly classified the disease. The citrus pest automatic diagnosis web system using the model proposed in this study plays a useful auxiliary role in recognizing and classifying citrus diseases. This can, in turn, help improve the overall quality of citrus fruits.

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Arif, Alfis. « A SISTEM PAKAR HAMA DAN PENYAKIT TANAMAN JERUK GERGA PAGAR ALAM MENGGUNAKAN METODE EUCLIDEAN DISTANCE BERBASIS WEBSITE ». Jurnal Teknologi Informasi Mura 11, n^o 02 (16 décembre 2019) : 68–75. http://dx.doi.org/10.32767/jti.v11i02.610.

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Penyediaan sistem informasi tentang penyakit Tanaman Jeruk di Kota Pagaralam masih bersifat manual sehingga tak berfungsi secara maksimal saat penyebaran informasi baik ke petani, penyuluh, & pengguna lainnya. Gangguan penyakit merupakan masalah penting yang dihadapi petani dalam usaha tani buah jeruk, selain menurunkan hasil produksi serangan penyakit juga menurunkan kualitas hasil. Oleh karena itu untuk mengetahui penyakit apa yang menyerang tanaman Jeruk maka dibutuhkan suatu sistem informasi identifikasi penyakit pada tanaman buah Jeruk berbasis website. Dengan aplikasi ini diharapkan petani dapat terbantu dalam mendiagnosis hama & penyakit yang sedang menyerang tanaman jeruknya, sehingga bisa juga mengetahui penanganannya dan mencegah serangan yang lebih luas. Metode kegiatan yang digunakan pada pembuatan sistem pakar diagnosis penyakit jeruk ini adalah analisis situasi, koleksi pengetahuan, perancangan, testing & evaluasi, dokumentasi serta pemeliharaan. Sistem pakar ini menggunakan metode Euclidean Distance atau jarak terpendek dari setiap gejala yang ada terhadap serangan hama atau penyakit jeruk. Hasil yang diperoleh adalah sebuah sistem informasi identifikasi hama dan penyakit pada tanaman buah Jeruk berbasis website. Kata kunci : Hama, Jeruk, Pakar, Euclidean Distance Abstract Provision of information systems about Citrus Disease in Pagaralam City is still manual so that it does not function optimally when disseminating information to farmers, extension workers & other users. Disease is an important problem faced by farmers in the farming of citrus fruits, in addition to reducing the production of disease attacks also reduces the quality of yields. Therefore, to find out what diseases that attack citrus plants, we need a system for identifying information on diseases in citrus fruit based on a website. With this application farmers are expected to be able to assist in diagnosing pests & diseases that are attacking their citrus plants, so they can also know how to handle them and prevent wider attacks. The method of activities used in making this expert system for diagnosis of orange disease are situation analysis, knowledge collection, design, testing & evaluation, documentation and maintenance. This expert system uses the Euclidean Distance method or the shortest distance from each symptom that exists against pests or citrus diseases. The results obtained are a website-based information system for identifying pests and diseases in citrus fruit plants. Keywords : Pests, Oranges, Experts, Euclidean Distance

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Michael, Githae, George O. Ong’amo, John Nderitu, Gillian W. Watson et Wanja Kinuthia. « Diversity of scale insects (Hemiptera : Coccomorpha) attacking citrus trees in Machakos, Makueni, Kilifi and Kwale Counties, Kenya ». Journal of Agricultural Science and Practice 6, n^o 3 (30 juin 2021) : 79–85. http://dx.doi.org/10.31248/jasp2021.275.

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Citrus farming is a major source of revenue for large and small-scale farmers in Kenya. Citrus production is confronted with threats from pests and diseases. Surveys of citrus farms in Kilifi, Kwale, Machakos and Makueni counties, Kenya in July/August (dry season) and in November/December (wet season), 2019 were conducted to identify scale insect pests (Hemiptera: Coccomorpha) attacking the trees (Sapindales: Rutaceae), and their related biota. A total of 22 scale insect species belonging to four families, namely Diaspididae (armoured scales), Coccidae (soft scales), Pseudococcidae (mealybugs), and Monophlebidae (giant mealybugs) were found infesting citrus trees in the two regions surveyed. Among the scale insects reported, four species were newly introduced in Kenya; three armoured scales Parlatoria ziziphi (Lucas), Parlatoria pergandii (Comstock), Aonidiella comperei (McKenzie), and a soft scale, Pulvinaria polygonata (Cockerell). The scale insects were closely associated with predators (coccinellids and lacewings) and attendant ants. This information will be helpful in the development of efficient management strategies against the scale insect pests, thus improving citrus production in Kenya. The scale insect pests identified in this study will be useful to plant quarantine facilities in Kenya to help to prevent and detect accidental introductions of exotic scale insect species.

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Xing, Shuli, Marely Lee et Keun-kwang Lee. « Citrus Pests and Diseases Recognition Model Using Weakly Dense Connected Convolution Network ». Sensors 19, n^o 14 (19 juillet 2019) : 3195. http://dx.doi.org/10.3390/s19143195.

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Pests and diseases can cause severe damage to citrus fruits. Farmers used to rely on experienced experts to recognize them, which is a time consuming and costly process. With the popularity of image sensors and the development of computer vision technology, using convolutional neural network (CNN) models to identify pests and diseases has become a recent trend in the field of agriculture. However, many researchers refer to pre-trained models of ImageNet to execute different recognition tasks without considering their own dataset scale, resulting in a waste of computational resources. In this paper, a simple but effective CNN model was developed based on our image dataset. The proposed network was designed from the aspect of parameter efficiency. To achieve this goal, the complexity of cross-channel operation was increased and the frequency of feature reuse was adapted to network depth. Experiment results showed that Weakly DenseNet-16 got the highest classification accuracy with fewer parameters. Because this network is lightweight, it can be used in mobile devices.

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Xing, Shuli, et Malrey Lee. « Classification Accuracy Improvement for Small-Size Citrus Pests and Diseases Using Bridge Connections in Deep Neural Networks ». Sensors 20, n^o 17 (3 septembre 2020) : 4992. http://dx.doi.org/10.3390/s20174992.

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Due to the rich vitamin content in citrus fruit, citrus is an important crop around the world. However, the yield of these citrus crops is often reduced due to the damage of various pests and diseases. In order to mitigate these problems, several convolutional neural networks were applied to detect them. It is of note that the performance of these selected models degraded as the size of the target object in the image decreased. To adapt to scale changes, a new feature reuse method named bridge connection was developed. With the help of bridge connections, the accuracy of baseline networks was improved at little additional computation cost. The proposed BridgeNet-19 achieved the highest classification accuracy (95.47%), followed by the pre-trained VGG-19 (95.01%) and VGG-19 with bridge connections (94.73%). The use of bridge connections also strengthens the flexibility of sensors for image acquisition. It is unnecessary to pay more attention to adjusting the distance between a camera and pests and diseases.

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Purba, Endang Christine, et Bambang S. Purwoko. « TEKNIK PEMBIBITAN, PEMUPUKAN, DAN PENGENDALIAN HAMA PENYAKIT TANAMAN KOMODITI JERUK SIAM (Citrus nobilis var. microcarpa) DI KECAMATAN SIMPANG EMPAT DAN KECAMATAN PAYUNG, KABUPATEN KARO, SUMATRA UTARA, INDONESIA ». Pro-Life 6, n^o 1 (5 mars 2019) : 66. http://dx.doi.org/10.33541/pro-life.v6i1.940.

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Citrus is one of the horticultural commodities that has been a focus of development in 2018. Citrus is the fourth largest commodity in the percentage of Indonesia fruit production in 2014. In 2014, citrus fruit production in Indonesia was 1,785,256 tons or around 9.01% of national fruit production. Karo Regency is a citrus production center in North Sumatra, Indonesia. According to the Direktorat Jendral Hortikultura (2015) the production of citrus commodities was 173.921 tons (53,30%). In 2014, there were 3,150,060 productive citrus trees with a harvested area of 7,875 ha and a production of 500,243 tons in North Sumatra. One of the varieties grown by farmers in Karo Regency is Siam. High productivity of siam is certainly also influenced by seedlings, fertilization and controlling the pests. To determine this, research has been conducted on farmers in Simpang Empat and Payung Districts, Karo Regency, North Sumatra, Indonesia. To get quality Siam seeds, farmers in two research locations used Japansche citroen plants as rootstock because they were resistant to disease and drought. Fertilization of siam uses inorganic fertilizer as much as 3-4 months, while organic fertilizer as much as 10 months. The control of pests of siam citrus is done mechanically and chemically. Pests and diseases that usually attack siam are Bractocera spp, black lice, fruit borers, fungus and powdery mildew. Keywords: cultivation, seedling, fertilizer, pest, productivity, orange, Citrus nobilis

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Resiani, Ni Made Delly, Ni Putu Sutami et A. A. N. B. Kamandalu. « Innovations in healthy citrus garden management to reduce major pests and diseases and increase incomes of citrus farmers ». E3S Web of Conferences 361 (2022) : 02007. http://dx.doi.org/10.1051/e3sconf/202236102007.

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Healthy citrus garden management is an effort to optimize citrus yields. The research aims to suppress major pests and diseases and increase yields and incomes of citrus farmers. The research was conducted in Kintamani, Bali in January 2017-December 2020. The study was conducted in pairs in the form of 1 block of garden technology innovation treatment of healthy citrus gardens and 1 block of farmers' existing gardens. Plant samples per block were determined by purposive sampling. The results showed that the treatment had a significant effect on the abundance of fruit fly populations, diplodia infection, crop yields and farm income. There was a decrease in fruit fly population abundance and diplodia infection by 9.20 and 33.60%, the average citrus fruit yield was 23.71 t/ha. / year, there is an increase in citrus farming income by 97.19%/ha/year due to the innovation of healthy citrus gardens. Based on the calculation results, the R/C ratio and MBCR values were 1.96 and 2.55 for innovations with components of healthy citrus garden management. It is concluded that the technological innovation of healthy citrus gardens is feasible to be developed with the same type of agroecosystem.

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Gairhe, Biwek, Ramdas Kanissery et Brent Sellers. « Citrus Nursery Production Guide, Chapter 8 : Stock Plant and Tree Production : c) Weed Management in Citrus Nurseries ». EDIS 2019, n^o 5 (24 octobre 2019) : 7. http://dx.doi.org/10.32473/edis-hs1344-2019.

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All citrus nursery stock in Florida is raised in enclosed greenhouses. It is not uncommon for weeds to grow in containers, where they compete with citrus seedlings, and on greenhouse floors, where they can harbor pests and diseases. This new 7-page publication of the UF/IFAS Horticultural Sciences Department provides descriptions of a few commonly found weeds in citrus nurseries and good weed management practices. Written by Biwek Gairhe, Ramdas Kanissery, and Brent Sellers, this article is chapter 8c of the forthcoming Citrus Nursery Production Guide. https://edis.ifas.ufl.edu/hs1344

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Thomas, Michael B., Jonathan H. Crane, James J. Ferguson, Howard W. Beck et Joseph W. Noling. « Two Computer-based Diagnostic Systems for Diseases, Insect Pests, and Physiological Disorders of Citrus and Selected Tropical Fruit Crops ». HortTechnology 7, n^o 3 (juillet 1997) : 293–98. http://dx.doi.org/10.21273/horttech.7.3.293.

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The TFRUIT·Xpert and CIT·Xpert computerbased diagnostic programs can quickly assist commercial producers, extension agents, and homeowners in the diagnosis of diseases, insect pest problems and physiological disorders. The CIT·Xpert system focuses on citrus (Citrus spp.), whereas the TFRUIT·Xpert system focuses on avocado (Persea americana Mill.), carambola (Averrhoa carambola L.), lychee (Litchi chinensis Sonn.), mango (Mangifera indica L.), papaya (Carica papaya L.), and `Tahiti' lime (Citrus latifolia Tan.). The systems were developed in cooperation with research and extension specialists with expertise in the area of diagnosing diseases, disorders, and pest problems of citrus and tropical fruit. The systems' methodology reproduces the diagnostic reasoning process of these experts. Reviews of extension and research literature and 35-mm color slide images were completed to obtain representative information and slide images illustrative of diseases, disorders, and pest problems specific to Florida. The diagnostic programs operate under Microsoft-Windows. Full-screen color images are linked to symptoms (87 for CIT·Xpert and 167 for TFRUIT·Xpert) of diseases, disorders, and insect pest problems of citrus and tropical fruit, respectively. Users can also refer to summary documents and retrieve management information from the Univ. of Florida's Institute of Food and Agricultural Sciences extension publications through hypertext links. The programs are available separately on CD-ROM and each contains over 150 digital color images of symptoms.

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Plus de sources

Thèses sur le sujet "Citrus Diseases and pests"

Wright, Glenn C., et John Begeman. « Diagnosing Home Citrus Problems ». College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2009. http://hdl.handle.net/10150/144796.

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6 pp.
Low Desert Citrus Varieties; Irrigating Citrus Trees
Diagnosing Home Citrus Problems includes information on all the commonly encountered dooryard citrus problems encountered in Arizona. Problems/disorders are grouped into three catagories: problems with fruit, problems with leaves, and problems with stems, branches and entire tree. Symptoms, causes and control measures are given for each disorder.

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Phiri, Zanele Penelope. « Creasing studies in citrus ». Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4219.

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Thesis (MScAgric (Horticulture))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Creasing, also known as albedo breakdown, is a preharvest disorder that affects the albedo of citrus fruit causing creases on the surface of the fruit. It is a recurrent problem in Navel and Valencia oranges and can cause individual orchard losses which often exceed 50%. Although the contributing factors are known, the physiological basis of creasing development is unresolved and the current control measures do not prevent creasing satisfactory. Hence, better control measures and further understanding of the physiology of creasing development is required. The objective of this two-year study was to determine if the position of fruit in a tree, light and carbohydrate manipulation techniques, and albedo mineral nutrients influence creasing development. Furthermore, the most effective application timing of gibberellic acid (GA3) with the least negative effect on fruit rind colour development and the effectiveness of cytokinins, other products and different root biostimulants to reduce creasing incidence were evaluated. The position of fruit in the tree and light influenced the development of creasing and the distribution of mineral nutrients in the albedo. Creasing incidence was higher on the south side than on the north side of the tree and fruit from the inside sub-sectors had a greater creasing incidence compared to fruit from the outside sub-sectors. The shady part of outside fruit was more creased compared to the sunny part of the fruit and covering fruit with brown paper bags increased creasing severity. The light manipulation techniques used on the leaves and fruit increased the nitrogen (N), phosphorus (P), potassium (K) and manganese (Mn) concentrations in the albedo and differences in the albedo mineral nutrients amongst the sub-sectors evaluated were observed, but creasing severity or creasing incidence was not significantly correlated with the albedo mineral concentrations at harvest. Albedo mineral concentrations earlier in the season may play a role in creasing development, as creasing severity was significantly correlated with copper (Cu), K, and Mn concentrations in the albedo during stage II of fruit development. Creasing incidence and albedo mineral concentrations were not affected by any of the carbohydrate manipulation techniques used in this study. The incidence and severity of creasing was significantly reduced, with a minor negative effect on fruit rind colour development, by the application of GA3, from mid November to mid January. Localised fruit application of CPPU [N-(2-chloro-4-pyridyl)-N-phenylurea], MaxCel (6- Benzyladenine) and CPPU in combination with calcium after physiological fruit drop reduced the incidence and severity of creasing, although creasing incidence was not significantly different from the control. The application of Messenger®, AVG (aminoethoxyvinylglycine) and different root biostimulants did not reduce creasing incidence. The results showed that cytokinins could reduce creasing incidence and justify further studies on application and uptake efficiency. The use of different root biostimulants are not recommended, but it is suggested that treatment effects may be more pronounced over a longer period.
AFRIKAANSE OPSOMMING: Kraakskil is ‘n vooroes abnormalitiet wat die albedo van sitrusvrugte affekteer, deur krake op die oppervlak van vrugte te veroorsaak. Dit is ‘n algemene probleem in Navel en Valencia lemoene en kan boordverliese van tot 50% of soms hoër veroorsaak. Alhoewel die bydraende faktore bekend is, is die fisiologiese basis van kraakskil ontwikkeling onopgelos en die beskikbare beheermaatreëls is nie bevredigend nie. Dus, beter beheermaatreëls en ‘n beter begrip van die fisiologie van kraakskil ontwikkeling is nodig. Die doel van die twee-jaar studie was om te bepaal of die posisie van vrugte in ‘n boom, lig en koolhidraat manipulasie tegnieke en minerale elemente in die albedo, kraakskil ontwikkeling beïnvloed. Die mees effektiewe toedieningstyd van gibberelliensuur (GA3) sonder ‘n negatiewe effek op vrugkleur is bepaal en die effektiwiteit van sitokiniene, ander produkte en verskillende wortel biostimulante om kraakskil voorkoms te verminder, is geëvalueer. Die posisie van vrugte in ‘n boom en lig het kraakskil ontwikkeling en die verspreiding van minerale element in die albedo beïnvloed. Kraakskil voorkoms was hoër aan die suidekant van die boom as aan die noordekant en vrugte in die binnekant van die boom het ‘n groter kraakskil voorkoms as vrugte in die buitekant van die boom gehad. Die skadukant van buitevrugte het meer kraakskil gehad as die sonkant en die toemaak van vrugte met ‘n bruin papiersak het die graad van kraaksil verhoog. Die lig manipulasie tegnieke wat op die blare en vrugte gebruik is, het die stikstof (N), fosfaat (P), kalium (K) en mangaan (Mn) konsentasies in die albedo verhoog en verskille in die albedo minerale elemente tussen sub-sektore is waargeneem, maar betekenisvolle korrelasies is nie tussen die graad en voorkoms van kraakskil en die albedo minerale element konsentrasies by oestyd waargeneem nie. Albedo minerale element konsentrasies vroeër in die seisoen mag ‘n rol speel by kraakskil ontwikkeling, omdat die graad van kraakskil betekenisvol gekorreleer was met albedo koper (Cu), K, en Mn konsentrasies tydens fase II van vrugontwikkeling. Kraakskil voorkoms en albedo minerale element konsentrasies is nie deur enige van die koolhidraat manipulasie tegnieke geaffekteer nie. Die voorkoms en graad van kraakskil is betekenisvol verlaag, met ‘n geringe negatiewe effek op vrugkleur, deur die toediening van GA3 vanaf mid November tot mid Januarie. Gelokaliseerde vrugtoedienings van CPPU [N-(2-chloro-4-piridiel)-N-phenielureum], MaxCel (6- Bensieladenien) en CPPU saam met kalsium na fisiologiese vrugval het die voorkoms en graad van kraakskil verlaag, alhoewel kraakskil voorkoms nie betekenisvol van die kontrole verskil het nie. Die toediening van Messenger®, AVG (amino etoksievinielglisien) en veskillende wortel biostimulante het nie kraakskil voorkoms verlaag nie. Die resultate het getoon dat sitokiniene kraakskil voorkoms kan verlaag en verdere studies op die toediening en opname effektiwiteit word aanbeveel. Die gebruik van verskillende wortel biostimulante word nie aanbeveel nie, maar die effek behoort meer sigbaar te wees na ‘n langer periode van behandeling.

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Van, der Walt Rachel. « Identifying volatile emissions associated with False Codling Moth infested citrus fruit ». Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1020056.

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False codling moth is a known pest of economic importance to many cultivated crops in South Africa and Africa south of the Sahara, and is particularly severe on citrus. If the fruit is infested just before harvest the chances of detecting signs of infestation are very low. As a result, the risk of packaging infested fruit and exporting them as healthy fruit is high. It is therefore a priority to develop a post-harvest technique for detection of False codling moth in citrus fruit at different levels of infestation in order to reduce phytosanitary risk. Compounds released and detected were indicative of infestation and were not insect produced but naturally produced fruit volatiles emitted at higher levels as a result of the insect within the fruit. Five major volatile compounds of interest were released by the infested oranges. These major volatile compounds include D-limonene, 3,7-dimethyl-1,3,6-octatriene, (E)-4,8-dimethyl-1,3,7-nonatriene, caryophyllene and naphthalene. Limonene was one of the most abundant volatile compounds released by the infested citrus fruit. Naphthalene, which is possibly produced due to larval feeding and development within the fruit maintained higher concentrations than controls throughout the infestation within the fruit. Naphthalene would be a good indicator of False codling moth infestation, however, not primarily for early infestation detection. A significantly higher concentration of D-limonene, 3,7-dimethyl-1,3,6-octatriene, (E)-4,8-dimethyl-1,3,7-nonatriene and naphthalene was detected using the SEP over the SPME technique. The application of an SPME procedure and the utilization of this method for detection of volatiles present in the headspace of intact infested fruit are evaluated and the possible volatile compounds diagnostic of Thaumatotibia leucotreta infestation of orange fruit and differences in volatile compound response in different orange varieties is discussed.

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Knight, Toby George. « Investigation of the physiological basis of the rind disorder oleocellosis in Washington navel orange (Citrus sinensis [L.] Osbeck) ». Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09AHP/09ahpk71.pdf.

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Includes bibliographical references (leaves 152-164) Microscopy investigations into the oil glands, localisation of the rind oils and the development of oleocellosis have been carried out in Washington navel orange (Citrus sinensis [L.] Osbeck). Aims to develop an improved understanding of the physiological basis of the rind disorder.

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Wakgari, Waktola (Waktola Muleta). « Biology, ecology and management of white wax scale, Ceroplastes destructor Newstead (Hemiptera : Coccidae), on citrus and syzygium ». Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51637.

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Thesis (PhD)--University of Stellenbosch, 2000.
ENGLISH ABSTRACT: The population density of the white wax scale, Ceroplastes destructor Newstead, has increased since 1994 in certain areas of Western and parts of Eastern Cape Provinces of South Africa where citrus is grown, particularly on Citrus reticulata (Blanco). A study was conducted to investigate its morphology, biology and ecology as contributions to the development of a sound integrated management programme. Characteristics of the immature stages and adult females were described and illustrated from field-collected and slide-mounted specimens. A key to the different stages and morphometeric characteristics useful for separating them are provided. No significant differences in female fecundity were found between orchards (P > 0.05). However, fecundity varied significantly between female size classes from the same orchard (P < 0.001). Female body-size also differed significantly between orchards (P < 0.05) and was significantly positively correlated with fecundity (P < 0.01). C. destructor has one discrete generation per year in South Africa. Oviposition commenced in November and continued through to the end of December with a few females ovipositing until mid January. Population density of the second instar peaked in February while the third instar extended from March to the end of July, followed by a peak population of adults in August. Seven primary and three secondary parasitoids, as well as four predator species attacking C. destructor were identified. Aprostocetus (= Tetrastichus) ceroplastae (Girault) was the dominant species, accounting for 78.87% of the total primary parasitoids reared. Peak numbers of parasitoids and predators were synchronized with peak emergence of susceptible scale stages, indicating that the host-parasitoid/predator system contained a density-dependent regulatory mechanism. Key mortality factors varied slightly between two of the orchards. Key stage mortality determined from a cohort life table was generally in the third instar (LIlI) and preovipositional female (POF) stage. Significant density-dependent mortality factors were demonstrated for the first instar (LI) and PDF stage. Dispersal of C. destructor is by first instar nymphs and the numbers caught on a series of yellow sticky traps varied significantly between crawler densities at the source, trap distances and trap directions from the source (P < 0.001). The numbers caught were positively correlated to the initial crawler density at the source (P < 0.01), suggesting that dispersal was density dependent. Trap distance and the numbers caught were inversely correlated (P < 0.01). Evaluation of effects of different densities of C. destructor on growth, survivorship and reproduction of scales as well as on leaf bearing ability of trees and area of leaf surface covered with sooty mould fungus was carried out on naturally infested Syzygium (= Eugenia) malaccensis (L.) plants. Scale body size and fecundity were inversely related to scale density (P < 0.01), suggesting density-dependent intraspecific competition. Scale survivorship generally declined with increasing density whereas scale parasitism and predation were positively correlated with density (P < 0.05). At high scale densities production of new leaves was significantly reduced (P < 0.01), reducing the resource base for subsequent generations of scale. Scale density and leaf area covered with sooty mould fungus were significantly positively correlated (P < 0.05). The toxicity of four synthetic insecticides against the three immature stages of C. destructor and of eight insecticides against the parasitoid A. ceroplastae was evaluated. Development of the first and second instars of C. destructor was completely arrested by the chemicals. Female fecundity, fertility and body sizes of survivors of treatments applied at the LIII stage were not significantly affected by any of the chemicals (P > 0.05). All the chemicals exhibited high toxicity to A. ceroplastae and hence are not recommended for integrated management of C. destructor in citrus orchards where A. ceroplastae plays an important role.
AFRIKAANSE OPSOMMING: Die populasiedigtheid van die witwasdopluis, Ceroplastes destructor Newstead, het sedert 1994 toegeneem in sekere gebiede van die Weskaap en Ooskaap provinsies van Suid-Afrika waar sitrus verbou word, veralop Citrus reticulata (Blanco). 'n Studie van hierdie insek se morfologie, biologie en ekologie is onderneem as bydrae tot die ontwikkeling van 'n geïntegreerde bestuursprogram. Die karaktertrekke van die onvolwasse stadia en die volwasse wyfies is beskryf en geïllustreer vanaf eksemplare wat in die veld versamel is en op g1asplaatjies gemonteer is. 'n Sleutel vir die verskillende stadia en morfometriese kenmerke wat nuttig is om hulle te onderskei, word voorsien. Geen beduidende verskille in die vrugbaarheid van wyfies van verskillende boorde is gevind nie (P < 0.05). Vrugbaarheid het egter betekenisvol verskil by die verskillende grootteklasse van wyfies uit dieselfde boord (P < 0.001). Die liggaamsgrootte van wyfies uit verskillende boorde het betekenisvol verskil (P < 0.05) en was betekenisvol positief gekorreleer met vrugbaarheid (P < 0.01). C. destructor het een generasie per jaar in Suid-Afrika. Eierlegging het in November begin en aangehou tot aan die einde van Desember, met enkele wyfies wat nog tot in middel Januarie eiers gelê het. Die populasiedigtheid van die tweede instar het 'n hoogtepunt in Februarie bereik, terwyl die derde instar van Maart tot aan die einde van Julie geduur het, gevolg deur 'n piekbevolking van volwassenes in Augustus. Sewe primêre en drie sekondêre parasitoïde asook vier predator spesies wat C destructor aanval, is geïdentifiseer. Aprostocetus (=Tetrastichus) ceroplastae (Girault) was die dominante spesies wat 78.87% van die totale aantal primêre parasitoïde wat uitgeteel is, uitgemaak het. Die pieke in die getalle van parasitoïde en predatore was gesinchroniseer met pieke in die verskyning van die gevoelige stadia, wat dui op die aanwesigheid van 'n digtheidsafhanklike regulatoriese meganisme. Die sleutel mortaliteitsfaktore het effens gevarieer tussen twee van die boorde. Die sleutelstadium van mortaliteit, soos bepaal m.b.v. 'n kohort lewenstabel, was gewoonlik die derde instar (LIlI) en die preoviposisionele wyfie (POW). Betekenisvolle digtheidsafhanklike mortaliteitsfaktore IS aangetoon vir die eerste instar (LI) en die POW. Die verspreiding van C.destructor vind plaas deur die eerste instar nimfe en die getalle wat op 'n reeks van taai geel valle gevang is, het betekenisvol gewissel volgens kruiperdigthede by die bron, asook die afstand en rigting van die valle vanaf die bron (P < 0.001). Die getalle wat gevang is, was positief gekorreleer met die aanvanklike kruiperdigtheid by die bron (P < 0.01), wat daarop dui dat verspreiding digtheidsafhanklik was. Die afstand van die valle en die aantal wat gevang is, was omgekeerd gekorreleer (P < 0.01). 'n Evaluering van die invloed van verskillende digthede van C. destructor op die groei, oorlewing en reproduksie van dopluise, asook die vermoë van bome om blare te dra en die area van die blaaroppervlak wat met roetskimmel besmet is, is uitgevoer op plante van Syzygium (= Eugenia) malaccensis (L.) met 'n natuurlike besmetting. Die liggaamsgrootte en vrugbaarheid van die dopluise was omgekeerd gekorreleer met hulle digtheid (P < 0.01), wat dui op digtheidsafhanklike intraspesifieke kompetisie. Die oorlewing van die dopluise het oor die algemeen afgeneem met toenemende digtheid, terwyl parasitisme en predasie positief gekorreleer was met digtheid (P < 0.05). By hoë dopluisdigthede het die produksie van nuwe blare betekenisvol afgeneem (P < 0.01), wat die hulpbronbasis vir daaropvolgende generasies van dopluise verswak. Die dopluisdigtheid en blaaroppervlak wat met roetskimmel bedek was, was positief gekorreleer (P < 0.05). Die toksisiteit van vier sintetiese insektemiddels teenoor die drie onvolwasse stadia van C. destructor en van agt insektemiddels teenoor die parasitoïd A. ceroplastae is geëvalueer. Die ontwikkeling van die eerste en tweede instars van C. destructor is heeltemal stopgesit deur die middels. Die fekunditeit, fertiliteit en liggaamsgrootte van wyfies wat toedienings op die LIIl stadium oorleef het, is nie betekenisvol ge-affekteer deur enige van die middels nie (P < 0.05). Al die middels was baie toksies teenoor A. ceroplastae en word dus nie aanbeveel vir die geïntegreerde bestuur van C. destructor waar A. ceroplastae 'n belangrike rol speel nie.

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Ceballo, Flor Angel Aquino. « An investigation into why coccidoxenoides peregrinus (timberlake) (hymenoptera:encyrtidae) is an effective biological control agent in Queensland citrus / ». St. Lucia, Qld, 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16498.pdf.

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FitzGerald, Véronique Chartier. « Screening of entomopathogenic fungi against citrus mealybug (Planococcus citri (Risso)) and citrus thrips (Scirtothrips aurantii (Faure)) ». Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1020887.

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Mealybugs (Planococcus citri) and thrips (Scirtothrips aurantii) are common and extremely damaging citrus crop pests which have proven difficult to control via conventional methods, such as chemical pesticides and insect growth regulators. The objective of this study was to determine the efficacy of entomopathogenic fungi against these pests in laboratory bioassays. Isolates of Metarhizium anisopliae and Beauveria bassiana from citrus orchards in the Eastern Cape, South Africa were maintained on Sabouraud Dextrose 4% Agar supplemented with Dodine, chloramphenicol and rifampicin at 25°C. Infectivity of the fungal isolates was initially assessed using 5th instar false codling moth, Thaumatotibia leucotreta, larvae. Mealybug bioassays were performed in 24 well plates using 1 x 107 ml-1 conidial suspensions and kept at 26°C for 5 days with a photoperiod of 12 L:12 D. A Beauveria commercial product and an un-inoculated control were also screened for comparison. Isolates GAR 17 B3 (B. bassiana) and FCM AR 23 B3 (M. anisopliae) both resulted in 67.5% mealybug crawler mortality and GB AR 23 13 3 (B. bassiana) resulted in 64% crawler mortality. These 3 isolates were further tested in dose-dependent assays. Probit analyses were conducted on the dose-dependent assays data using PROBAN to determine LC₅₀ values. For both the mealybug adult and crawlers FCM AR 23 B3 required the lowest concentration to achieve LC₅₀ at 4.96 x 10⁶ conidia ml-1 and 5.29 x 10⁵ conidia ml-1, respectively. Bioassays on adult thrips were conducted in munger cells with leaf buds inoculated with the conidial suspensions. Isolate GAR 17 B3 had the highest mortality rate at 70% on thrips while FCM AR 23 B3 resulted in 60% mortality. Identification of the isolates, FCM AR 23 B3, GAR 17 B3 and GB AR 23 13 3, were confirmed to be correct using both microscopic and molecularly techniques. ITS sequences were compared to other sequences from GenBank and confirmed phylogenetically using MEGA6. Mealybug infection was investigated using scanning electron microscopy, mycosis was confirmed but the infection process could not be followed due to the extensive waxy cuticle. These results indicate that there is potential for the isolates FCM AR 23 B3 and GAR 17 B3 to be developed as biological control agents for the control of citrus mealybug and thrips. Further research would be required to determine their ability to perform under field conditions.

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Wright, Jacqueline Gilda. « The role of endophytes in citrus stem end rots ». Thesis, Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19736654.

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Mathewson, Johanna. « Die insekplaagkompleks op sitrus te Vaalharts ». Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51706.

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Thesis (MSc)--Stellenbosch University, 2000.
Full text to be digitised and attached to bibliographic record.
ENGLISH ABSTRACT: The cultivation of citrus in the Vaalharts region is a fairly recent development. With the introduction of this crop, an insect pest complex has also developed in this region. The presence of these pests was studied in eleven orchards, planted with three citrus cultivars and of varying ages, distributed in the 300 square kilometer cultivation area. Each orchard was inspected for the presence of pests by making use of two weekly sampling techniques. Ten of the most important insect pests of citrus in the Vaalharts region are briefly described by refering to their general appearance, life cycles, feeding and pest status and economic threshold. For every pest various control options, including operational systems, crop cultivation, biological and chemical control, are discussed and, where applicable, illustrated by means of graphic presentations. The seasonal presence of the cirtrus pests in the Vaalharts region is tabulated and discussed individually. With these details as background, an insect pest management programme for citrus in the Vaalharts region is compiled.
AFRIKAANSE OPSOMMING: Die verbouing van sitrus in die Vaalhartsgebied is 'n redelik onlangse ontwikkeling. Gepaard met die nuwe gewas het daar ook 'n insekplaagkompleks in die gebied ontstaan. Die voorkoms van die plae is in elt .boorde, beplant met drie sitruskultivars en van verskillende ouderdomme, verspreid in die 300 vierkante kilometer verbouingsareaal, bestudeer. Elk van die boorde is weekliks ondersoek vir die aanwesigheid van plae deur van twee moniteringstegnieke gebruik te maak. Die tien belangrikste insekplae van sitrus in die Vaalhartsgebied word kortliks beskryf deur na hulle algemene voorkoms, lewenssiklus, voeding en plaagstatus en ekonomiese drempelwaardes asook die moniteringsmetodes wat gebruik is, te verwys. Vir elke plaag word beheeropsies, wat operasionele stelsels, gewasverbouing, bloloqlese en chemiese beheer insluit, bespreek wat, waar toepaslik, aan die hand van grafiese voorstellings gemustreer word. Die seisoenale aanwesigheid van die sitrusplae word in 'n tabel aangedui en individueel bespreek. Met die gegewens as agtergrond is 'n insekplaagbestuurprogram vir sitrus in die Vaalhartsgebied opgestel.

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Opoku-Debrah, John Kwadwo. « Geographic variation in the susceptibility of false colding Moth, Thaumatotibia Leucotreta, populations to a granulovirus (CrleGV-SA) ». Thesis, Nelson Mandela Metropolitan University, 2008. http://hdl.handle.net/10948/984.

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The false codling moth (FCM), Thaumatotibia (=Cryptophlebia) leucotreta (Meyrick) (Lepidoptera: Tortricidae) is a serious pest of citrus and other crops in Sub-Saharan Africa. The introduction of the Cryptophlebia leucotreta granulovirus (CrleGV-SA) Cryptogran and Cryptex (biopesticides) has proven to be very effective in the control of FCM. However, markedly lower susceptibility of some codling moth (CM), Cydia pomonella (L.) populations to Cydia pomonella granulovirus (CpGV-M), another granulovirus product used in the control of CM’s in Europe have been reported. Genetic differences between FCM populations in South Africa have also been established. It is therefore possible that differences in the susceptibility of these geographically distinct FCM populations to CrleGV-SA might also exist. To investigate this phenomenon, a benchmark for pathogenecity was established. In continuation of previous work with Cryptogran against the 1st and 5th instar FCM larvae, dose-response relationships were established for all five larval instars of FCM. In surface dose-response bioassays, the LC50 values for the 2nd, 3rd and 4th instars were calculated to be 4.516 x 104, 1.662 x 105 and 2.205 x 106 occlusion bodies (OBs)/ml, respectively. The LC90 values for the 2nd, 3rd and 4th instars were calculated to be 4.287 x 106, 9.992 x 106 and 1.661 x 108 OBs/ml, respectively. Susceptibility to CrleGV-SA was found to decline with larval stage and increase with time of exposure. The protocol was used in guiding bioassays with field collected FCM larvae. Laboratory assays conducted with Cryptogran (at 1.661 x 108 OBs/ml) against field collected FCM larvae from Addo, Kirkwood, Citrusdal and Clanwilliam as well as a standard laboratory colony, showed a significant difference in pathogenecity in only one case. This significant difference was observed between 5th instars from the Addo colony and 5th instars from the other populations. Four geographically distinct FCM colonies from Addo, Citrusdal, Marble Hall and Nelspruit were also established. Since Cryptogran and Cryptex are always targeted against 1st instar FCM larvae in the field, further comparative laboratory assays were conducted with the Addo colony and an old laboratory colony. Cryptogran was significantly more pathogenic than Cryptex against both the Addo and the old colony. However, a high level of heterogeneity was observed in responses within each population.

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Livres sur le sujet "Citrus Diseases and pests"

Whitmore, Susan. Citrus canker disease. Beltsville, Md : U.S. Dept. of Agriculture, National Agricultural Library, 1985.

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Whitmore, Susan. Citrus canker disease. Beltsville, Md : U.S. Dept. of Agriculture, National Agricultural Library, 1985.

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Whitmore, Susan. Citrus canker disease. Beltsville, Md : U.S. Dept. of Agriculture, National Agricultural Library, 1985.

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University of California (System). Division of Agriculture and Natural Resources, dir. Citrus production manual. Oakland, California : University of California, Agriculture and Natural Resources, 2014.

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Karasev, Alexander V., et Mark E. Hilf. Citrus tristeza virus complex and tristeza diseases. St. Paul, Minn : American Phytopathological Society, 2010.

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Vacante, Vincenzo. Citrus mites : Identification, bionomy and control. Cambridge, MA : CABI North American Office, 2010.

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United States. Animal and Plant Health Inspection Service. Help us find citrus greening disease. 2^e éd. [Riverdale, Md.?] : U.S. Dept. of Agriculture, Animal and Plant Health Inspection Service, 2010.

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Vacante, Vincenzo. Citrus mites : Identification, bionomy and control. Cambridge, MA : CABI North American Office, 2010.

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Vacante, Vincenzo. Citrus mites : Identification, bionomy and control. Cambridge, MA : CABI North American Office, 2010.

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United States. Animal and Plant Health Inspection Service. Huanglongbing, or citrus greening. 2^e éd. [Riverdale, Md.?] : U.S. Dept. of Agriculture, Animal and Plant Health Inspection Service, 2010.

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Chapitres de livres sur le sujet "Citrus Diseases and pests"

Neves, Marcos Fava, Vinícius Gustavo Trombin, Frederico Fonseca Lopes, Rafael Kalaki et Patrícia Milan. « Pests and diseases in the Brazil’s citrus belt ». Dans The orange juice business, 67. Wageningen : Wageningen Academic Publishers, 2011. http://dx.doi.org/10.3920/978-90-8686-739-4_17.

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Karamaouna, Filitsa, Panagiotis Mylonas, Dimitrios Papachristos, Dimitrios Kontodimas, Antonios Michaelakis et Eleftheria Kapaxidi. « Main Arthropod Pests of Citrus Culture and Pest Management in Greece ». Dans Integrated Management of Arthropod Pests and Insect Borne Diseases, 29–59. Dordrecht : Springer Netherlands, 2010. http://dx.doi.org/10.1007/978-90-481-8606-8_2.

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Zappalà, Lucia. « Citrus Integrated Pest Management in Italy ». Dans Integrated Management of Arthropod Pests and Insect Borne Diseases, 73–100. Dordrecht : Springer Netherlands, 2010. http://dx.doi.org/10.1007/978-90-481-8606-8_4.

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Thanassoulopoulos, C. C. « Diseases ». Dans Integrated Pest Control in Citrus-Groves, 583–85. London : CRC Press, 2021. http://dx.doi.org/10.1201/9781003079279-92.

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Campos-Herrera, Raquel, Robin J. Stuart, Fahiem El-Borai, Carmen Gutierrez et Larry Duncan. « Entomopathogenic Nematode Ecology and Biological Control in Florida Citrus Orchards ». Dans Integrated Management of Arthropod Pests and Insect Borne Diseases, 101–30. Dordrecht : Springer Netherlands, 2010. http://dx.doi.org/10.1007/978-90-481-8606-8_5.

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Jacas, Josep Anton, Filitsa Karamaouna, Rosa Vercher et Lucia Zappalà. « Citrus Pest Management in the Northern Mediterranean Basin (Spain, Italy and Greece) ». Dans Integrated Management of Arthropod Pests and Insect Borne Diseases, 3–27. Dordrecht : Springer Netherlands, 2010. http://dx.doi.org/10.1007/978-90-481-8606-8_1.

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Jacas, Josep Anton, et Alberto Urbaneja. « Biological Control in Citrus in Spain : From Classical to Conservation Biological Control ». Dans Integrated Management of Arthropod Pests and Insect Borne Diseases, 61–72. Dordrecht : Springer Netherlands, 2010. http://dx.doi.org/10.1007/978-90-481-8606-8_3.

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Salemo, M., et G. Cutuli. « Fungal and bacterial diseases of citrus in the Mediterranean region ». Dans Integrated Pest Control in Citrus-Groves, 243–48. London : CRC Press, 2021. http://dx.doi.org/10.1201/9781003079279-38.

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Albrigo, L. G., L. L. Stelinski et L. W. Timmer. « Arthropod pests. » Dans Citrus, 183–213. Wallingford : CABI, 2019. http://dx.doi.org/10.1079/9781845938154.0183.

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Catara, A., M. Davino, F. Russo et G. Terranova. « Virus and virus-like diseases of citrus, plant quarantine regulation, clonal and sanitary programs in the Mediterranean area and criteria for handling virus-free clones ». Dans Integrated Pest Control in Citrus-Groves, 295–304. London : CRC Press, 2021. http://dx.doi.org/10.1201/9781003079279-45.

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Actes de conférences sur le sujet "Citrus Diseases and pests"

Laisheng, Xiao, Wang Zhengxia, Peng Xiaohong, Wu Min et Yu Guangzhou. « Remote Diagnosis and Control Expert System for Citrus Agricultural Diseases and Insect Pests Based on BP Neural Network and WebGIS ». Dans 2009 Second International Conference on Intelligent Computation Technology and Automation. IEEE, 2009. http://dx.doi.org/10.1109/icicta.2009.738.

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Munkvold, Gary P. « Managing Diseases and Pests with Seed Treatments ». Dans Proceedings of the 16th Annual Integrated Crop Management Conference. Iowa State University, Digital Press, 2007. http://dx.doi.org/10.31274/icm-180809-893.

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Hunter, Wayne B. « Topical RNAi in citrus tree crops to control hemipteran pests ». Dans 2016 International Congress of Entomology. Entomological Society of America, 2016. http://dx.doi.org/10.1603/ice.2016.93851.

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Allan, Sandra A. « Citrus pests on olives in Florida : Should we be worried ? » Dans 2016 International Congress of Entomology. Entomological Society of America, 2016. http://dx.doi.org/10.1603/ice.2016.93472.

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Schall, Kelsey A. « Implications of Argentine ant management for biological control of the Asian citrus psyllid and other citrus pests ». Dans 2016 International Congress of Entomology. Entomological Society of America, 2016. http://dx.doi.org/10.1603/ice.2016.114044.

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Tumang, Gina S. « Pests and Diseases Identification in Mango using MATLAB ». Dans 2019 5th International conference on Engineering, Applied Sciences and Technology (ICEAST). IEEE, 2019. http://dx.doi.org/10.1109/iceast.2019.8802579.

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Khan, Ejaz, Muhammad Zia Ur Rehman, Fawad Ahmed et Muhammad Attique Khan. « Classification of Diseases in Citrus Fruits using SqueezeNet ». Dans 2021 International Conference on Applied and Engineering Mathematics (ICAEM). IEEE, 2021. http://dx.doi.org/10.1109/icaem53552.2021.9547133.

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Chen, Quan, Xin Liu, Caixia Dong, Tong Tong, Changcai Yang, Riqing Chen, Tengyue Zou et Xiaolang Yang. « Deep Convolutional Network for Citrus Leaf Diseases Recognition ». Dans 2019 IEEE Intl Conf on Parallel & Distributed Processing with Applications, Big Data & Cloud Computing, Sustainable Computing & Communications, Social Computing & Networking (ISPA/BDCloud/SocialCom/SustainCom). IEEE, 2019. http://dx.doi.org/10.1109/ispa-bdcloud-sustaincom-socialcom48970.2019.00215.

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Wang, Qiyao, Guiqing He, Feng Li et Haixi Zhang. « A novel database for plant diseases and pests classification ». Dans 2020 IEEE International Conference on Signal Processing, Communications and Computing (ICSPCC). IEEE, 2020. http://dx.doi.org/10.1109/icspcc50002.2020.9259502.

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Patel, Pruthvi P., et Dineshkumar B. Vaghela. « Crop Diseases and Pests Detection Using Convolutional Neural Network ». Dans 2019 IEEE International Conference on Electrical, Computer and Communication Technologies (ICECCT). IEEE, 2019. http://dx.doi.org/10.1109/icecct.2019.8869510.

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Rapports d'organisations sur le sujet "Citrus Diseases and pests"

Bar-Joseph, Moshe, William O. Dawson et Munir Mawassi. Role of Defective RNAs in Citrus Tristeza Virus Diseases. United States Department of Agriculture, septembre 2000. http://dx.doi.org/10.32747/2000.7575279.bard.

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This program focused on citrus tristeza virus (CTV), the largest and one of the most complex RNA-plant-viruses. The economic importance of this virus to the US and Israeli citrus industries, its uniqueness among RNA viruses and the possibility to tame the virus and eventually turn it into a useful tool for the protection and genetic improvement of citrus trees justify these continued efforts. Although the overall goal of this project was to study the role(s) of CTV associated defective (d)-RNAs in CTV-induced diseases, considerable research efforts had to be devoted to the engineering of the helper virus which provides the machinery to allow dRNA replication. Considerable progress was made through three main lines of complementary studies. For the first time, the generation of an engineered CTV genetic system that is capable of infecting citrus plants with in vitro modified virus was achieved. Considering that this RNA virus consists of a 20 kb genome, much larger than any other previously developed similar genetic system, completing this goal was an extremely difficult task that was accomplished by the effective collaboration and complementarity of both partners. Other full-length genomic CTV isolates were sequenced and populations examined, resulting in a new level of understanding of population complexities and dynamics in the US and Israel. In addition, this project has now considerably advanced our understanding and ability to manipulate dRNAs, a new class of genetic elements of closteroviruses, which were first found in the Israeli VT isolate and later shown to be omnipresent in CTV populations. We have characterized additional natural dRNAs and have shown that production of subgenomic mRNAs can be involved in the generation of dRNAs. We have molecularly cloned natural dRNAs and directly inoculated citrus plants with 35S-cDNA constructs and have shown that specific dRNAs are correlated with specific disease symptoms. Systems to examine dRNA replication in protoplasts were developed and the requirements for dRNA replication were defined. Several artificial dRNAs that replicate efficiently with a helper virus were created from infectious full-genomic cDNAs. Elements that allow the specific replication of dRNAs by heterologous helper viruses also were defined. The T36-derived dRNAs were replicated efficiently by a range of different wild CTV isolates and hybrid dRNAs with heterologous termini are efficiently replicated with T36 as helper. In addition we found: 1) All CTV genes except of the p6 gene product from the conserved signature block of the Closteroviridae are obligate for assembly, infectivity, and serial protoplast passage; 2) The p20 protein is a major component of the amorphous inclusion bodies of infected cells; and 3) Novel 5'-Co-terminal RNAs in CTV infected cells were characterized. These results have considerably advanced our basic understanding of the molecular biology of CTV and CTV-dRNAs and form the platform for the future manipulation of this complicated virus. As a result of these developments, the way is now open to turn constructs of this viral plant pathogen into new tools for protecting citrus against severe CTV terms and development of virus-based expression vectors for other citrus improvement needs. In conclusion, this research program has accomplished two main interconnected missions, the collection of basic information on the molecular and biological characteristics of the virus and its associated dRNAs toward development of management strategies against severe diseases caused by the virus and building of novel research tools to improve citrus varieties. Reaching these goals will allow us to advance this project to a new phase of turning the virus from a pathogen to an ally.

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Wilson, Charles, et Edo Chalutz. Biological Control of Postharvest Diseases of Citrus and Deciduous Fruit. United States Department of Agriculture, septembre 1991. http://dx.doi.org/10.32747/1991.7603518.bard.

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The objectives of this research were to develop control measures of postharvest diseases of citrus and deciduous fruits by using naturally-occurring, non-antibiotic-producing antagonists; study the mode of action of effective antagonists and optimize their application methods. Several antagonists were found against a variety of diseases of fruits and vegetables. One particularly effective yeast antagonist (US-7) was chosen for more in-depth studies. This antagonist outcompetes rot pathogens at the wound site for nutrients and space; it is better adapted than the pathogen to extreme environmental conditions such as temperature, humidity and osmotic changes, and is relatively resistant to common postharvest fungicides. Our data suggests that other modes of action may also be involved. These are induction of host resistance by the antagonists or its products, and direct interaction between the antagonists and the pathogen with the possible involvement of an extracellular material and/or cell wall degrading enzymes produced by the antagonist. However, these interactions were not fully elucidated. The antagonistic activity of US-7 and other biocontrol agents isolated, was enhanced by calcium salts. While the mode of action is not known, the addition of these salts had a significant effect both in laboratory experiments and in large-scale tests. Compatibility of the yeast antagonist with present packinghouse treatments and procedures was determined. An integrated control procedure was developed, utilizing the antagonists together with ultra-low dosages of fungicides and activity-enhancing additives. This cooperative research resulted in numerous publications describing the antagonistic agents. their mode of action and possible commercial application. Patents were developed from this research and a commercial company is pursuing the licensing of these patents and the testing of the procedure on a commercial scale. Our research findings have expanded the potential for using non-antibiotic-producing antagonistic microorganisms in the control of postharvest diseases of fruits and vegetables; thus meeting a critical need to find alternatives to the use of synthetic fungicides on food products.

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Solomon, J. D., T. D. Leininger, A. D. Wilson, R. L. Anderson, L. C. Thompson et F. I. McCracken. Ash pests : a guide to major insects, diseases, air pollution injury, and chemical injury. New Orleans, LA : U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station, 1993. http://dx.doi.org/10.2737/so-gtr-096.

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Kosiba, Alexandra, Emma Tait, Gene Desideraggio, Alyx Belisle, Clarke Cooper et James Duncan. Threats to the Urban Forest : The potential economic impacts of invasive forest pests and diseases in the Northeast. Forest Ecosystem Monitoring Cooperative, juin 2020. http://dx.doi.org/10.18125/8w9j42.

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Davis, Cristina, Amots Hetzroni, Alexander Aksenov, Michael J. Delwiche, Victoria Soroker et Victor Alchanatis. Development of a universal volatile compound detection technology for early recognition of pests and diseases in fruit trees. United States Department of Agriculture, janvier 2015. http://dx.doi.org/10.32747/2015.7600016.bard.

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Amanor, Kojo, Joseph Yaro, Joseph Teye et Steve Wiggin. Ghana’s Cocoa Farmers Need to Change Gear : What Policymakers Need to Know, and What They Might Do. Institute of Development Studies (IDS), mars 2022. http://dx.doi.org/10.19088/apra.2022.008.

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Cocoa farmers in Ghana face increasing challenges. In the past, many of them could make a living from cocoa thanks to the advantages – ‘forest rents’ – that initially apply when forest is cleared to create cocoa farms: fertile soils, few pests and diseases. With time, however, weeds invade, pests and diseases build up, and trees age. To maintain production requires more labour, more inputs and more skill. In the past, farmers would often abandon older groves and seek new forest to clear. As they did so, the frontier for cocoa farming moved westwards across Ghana to the remaining high forest. But by 2000 or so, no new forest was available. Farmers now have to manage aging stands of trees, clear weeds and parasites, and combat pests, fungi and diseases. In Suhum District in the east and in Juaboso District in the far west of Ghana, we talked to farmers. They understood the challenges they faced, and knew how to deal with some of them. But many were not farming their cocoa as well as they could, losing yields and income as a result. This brief provides a basis for policymakers to move forward in responding to the current challenges facing cocoa farmers.

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Chalutz, Edo, Michael Wisniewski, Samir Droby, Yael Eilam et Ilan Chet. Mode of Action of Yeast Biocontrol Agents of Postharvest Diseases of Fruits. United States Department of Agriculture, juin 1996. http://dx.doi.org/10.32747/1996.7613025.bard.

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In a previous BARD-supported study, three of the investigators of this research were involved in a study on biological control of postharvest diseases of citrus and deciduous fruits. Several naturally occurring, non-antibiotic producing yeast antagonists were identified. Application of some of these antagonists resulted in very high levels of biocontrol under laboratory conditions but lower efficacy in semi-commercial tests. It was felt that the lack of knowledge on the mode of action of the biocontrol agents was limiting their efficient use. The current study was aimed at narrowing this gap in our knowledge. Two specific objectives were outlined: to study the mechanism by which calcium salts enhance biocontrol activity and to determine the role, if any, of the yeast extracellular materials and/or enzymes which degrade fungal cell walls during the interaction between the antagonists, the pathogen and the host. CaCl2 but not MgCl2, inhibited spore germination, and germ-tube elongation of Botrytis cinerea, Penicillium expansum and P. digitatum in culture. It also inhibited the pectinolytic activity of the pathogens. Biocontrol of apple decay by isolate 182 of Candida oleophila, an effective biocontrol agent, was enhanced by the addition of CaCl2 whereas there was no effect on the biocontrol activity of isolate 247 of this yeast. Similarly, CaCl2 enhanced efficacy of the US-7 isolate of Pichia guilliermondii in reducing infection of P. digitatum in citrus fruit. CaCl2 by itself also reduced the infection of peel wounds and stimulated ethylene production by grapefruit peel. This antagonist exhibited a very high ability to maintain cytosolic Ca2+ homeostasis when exposed to high CaCl2 concentrations. It is postulated, therefore, that enhanced biocontrol activity by calcium is the result of direct inhibition of the pathogen by calcium ions on spore germination and metabolism and indirectly due to the ability of the biocontrol agent to maintain normal metabolism in the presence of high levels of calcium. The extracellular materials produced by P. guilliermondii in culture and on the fruit inhibited, at low concentrations, the pathogen in culture and reduced percent infection of the fruit. The direct inhibition of the pathogen by these materials may thus be involved in the mode of action of the antagonist. This study contributed to our knowledge on the action of calcium salts and the yeast antagonist extracellular materials on biocontrol activity and will contribute to a more efficient use of this technology in the control of postharvest diseases of fruits.

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Dawson, William O., et Moshe Bar-Joseph. Creating an Ally from an Adversary : Genetic Manipulation of Citrus Tristeza. United States Department of Agriculture, janvier 2004. http://dx.doi.org/10.32747/2004.7586540.bard.

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Citrus is one of the major agricultural crops common to Israel and the United States, important in terms of nutrition, foreign exchange, and employment. The economy of both citrus industries have been chronically plagued by diseases caused by Citrus tristeza virus (CTV). The short term solution until virus-resistant plants can be used is the use of mild strain cross-protection. We are custom designing "ideal" protecting viruses to immunize trees against severe isolates of CTV by purposely inoculating existing endangered trees and new plantings to be propagated as infected (protected) citrus budwood. We crossed the substantial technological hurdles necessary to accomplish this task which included developing an infectious cDNA clone which allows in vitro manipulation of the virus and methods to then infect citrus plants. We created a series of hybrids between decline-inducing and mild CTV strains, tested them in protoplasts, and are amplifying them to inoculate citrus trees for evaluation and mapping of disease determinants. We also extended this developed technology to begin engineering transient expression vectors based on CTV as tools for genetic improvement of tree crops, in this case citrus. Because of the long periods between genetic transformation and the ultimate assay of mature tree characteristics, there is a great need for an effective system that allows the expression or suppression of target genes in fruiting plants. Virus-based vectors will greatly expedite progress in citrus genetic improvement. We characterized several components of the virus that provides necessary information for designing virus-based vectors. We characterized the requirements of the 3 ’-nontranslated replication promoter and two 3 ’-ORF subgenomic (sg) mRNA controller elements. We discovered a novel type of 5’-terminal sgRNAs and characterized the cis-acting control element that also functions as a strong promoter of a 3 ’-sgRNA. We showed that the p23 gene controls negative-stranded RNA synthesis and expression of 3 ’ genes. We identified which genes are required for infection of plants, which are host range determinants, and which are not needed for plant infection. We continued the characterization of native dRNA populations and showed the presence of five different classes including class III dRNAs that consists of infectious and self-replicating molecules and class V dRNAs that contain all of the 3 ’ ORFs, along with class IV dRNAs that retain non-contiguous internal sequences. We have constructed and tested in protoplasts a series of expression vectors that will be described in this proposal.

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Chalutz, Edo, Charles Wilson, Samir Droby, Victor Gaba, Clauzell Stevens, Robert Fluhr et Y. Lu. Induction of Resistance to Postharvest Diseases and Extension of Shelf-Life of Fruits and Vegetables by Ultra-Violet Light. United States Department of Agriculture, février 1994. http://dx.doi.org/10.32747/1994.7568093.bard.

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Following preliminary observations by one of the collaborating scientists on this project and the completion of a 1-year, BARD-supported feasibility study (IS-1908-90F), this 3-year BARD project has been executed. The main objectives of the research were to elucidate biochemical and pathological aspects of UV-induced resistance in fruits and vegetables, to characterize physical and biological variables of induced resistance and delay of ripening, and to explore the application of the treatment as a control practice of postharvest diseases and shelf-life extension of fruits and vegetables. Our findings, which are detailed in numerous joint publications, have shown that the effect of UV-C light on induction of resistance and delay of ripening is a general one and of wide oddurrence. Apart from surface sterilization of the commodity, the reduction of decay of different fungi has been associated with and induced resistance phenomenon which gradually builds up within 24 to 48 hours after the UV treatment and can be reversed by visible light. In citrus, induced resistance has been associated with increased activity of the enzymes phenylalanine ammonia-lyase and peroxidase, and with the levels of endglucanase and chitinase. In tomato, resistance was correlated with the production of high levels of tomatine. Our study of some molecular aspects of the induced resistance in grapefruit has revealed the induction of a cDNA which represents a gene encoding for an isoflavone reductase-like protein that, in legumes, has been associated with phytoalexin biosynthesis. This gene was cloned and sequenced. Delay of ripening was associated in tomato with inhibition of ethylene production, carotenoid synthesis, and chlorophyll degradation and with the presence of high levels of polyamines. In peach fruit epiphytic populations of a yeast increased following the UV treatment. Pilot-size treatment and packing lines were constructed in the US and Israel to test the application of the UV treatment on a semi-commercial scale. Although effective in reduction of decay and delay of ripening, a number of problems will have to be addressed before practical application of this methodology can be realized. The main issues are associated with the temporal and variable response to the treatment, and its relationship to the maturity and date of harvest of the commodity.

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