Management of nitrogen fertilizer application for CITRUS trees was evaluated to obtain an enlightened understanding of plant nitrogen requirements, amount of fertilization needed, appropriate fertilization timing, and nitrogen uptake and storage in these plants. The knowledge thus obtained could be effectively exploited toward formulating recommendations that ensure optimized nitrogen fertilization. Mature CITRUS trees reportedly contain 500 to 1000 kg N/ha, 40 to 50 percent of which belongs in the leaves and fruits while only 15 to 20 kg N is deposited in their skeletal structure. These findings and the long-term survey of CITRUS fertilization experiments in Iran and elsewhere indicate that annual application of 200 kg N/ha seems sufficient for stable fruit production, improved fruit yield and quality, and proper tree growth and health. Moreover, it is found that 30-50% of this amount of N application will be incorporated into the fruits while about one tenth will be deposited and stored in the tree, with the balance between nitrogen uptake and consumption by the tree being secured by N leaching from the soil profile and lost as gas into the air. The results of an experiment with labeled fertilizers (15N) showed that the highest N-uptake rate in CITRUS trees occurred during the period from fruit set to fruit maturity and, further, that N uptake was very low during the post-harvest period, especially during minimum tree activity (winter) and the beginning of the growing season. This indicates that nitrogen storage in older tissues plays the greatest role in the growth and development of leaves, branches, flowers, and fruits at the beginning of the growing season when N uptake from the soil is still very low (i.e., when branches and flowers begin to sprout and fruits are in the form). It has also been reported that the nitrogen present in soil organic matter ranges from 1000 to 2000 kg/ha in orchard soils containing 1 to 2% O.M. and that both the soil nitrogen content and that stored in the tree bodies play important roles in regulating the supply of nitrogen to new organs (i.e., leaves, blooms, and fruitlets), especially in the beginning of the growing season. It follows that the purpose behind N fertilization should be to ensure stable production, proper tree growth, and improved fruit yield and quality such that soil application of fertilizers before the flowering and fruit set stages have no effects on the growth of spring buds or flowering and fruit setting in the current year. Producers are, therefore, recommended to start fertilizer application with a maximum of 10-15% of the annual plant requirement during the period prior to flowering and fruit setting, gradually increase application rate (by some percentage of the annual requirement) as determined by the phenology of fruit growth, and increase it to its maximum rate by the middle of the first stage up to the early second stage of fruit growth. Then, in the middle of the second stage of fruit growth, nitrogen rate should be reduced to its minimum or stopped altogether (depending on plant variety).

In recent years symptoms of viroid diseases, include stem pitting and gumming have highly incidenced in CITRUS ORCHARDS of Mazandaran. This study was conducted for determining the biological characteristics of CITRUS cachexia viroid strains in local tangerine ORCHARDS. 150 samples were collected from three important infected districts. Purification was carried out in CF-11 column. Presence of viroid was confirmed with RT-PCR using specific primers. For differentiation of Cachexia viroid isolates, 13 types of CITRUS were bark grafted on rootstock and symptoms were observed. RT-PCR data showed that 6% of samples were infected only with cachexia, while other samples showed mix infection with exocortis, tristeza and psorosis. According to the assay, the best indicator plant is the Mexican lime (CITRUS aurantifolia. Swing. ), which could express the typical symptoms of mild to severe infection. Also it is possible to separate severe strains from mild strains based on the symptoms on the local tangerine trees and gumming on the branches can be the primary basis for differentiation.

The orange Pulvinaria scale, Pulvinaria aurantii (Cockerell) is the most important pest of CITRUS in Mazandaran, Iran. The calculation of economic injury level is essential for the appropriate decision to pest control. The economic injury level (EIL) of P. aurantii on Washington navel orange was studied during two years (2011 and 2012) in Sari (north of Iran). In the first year, six treatments of different densities of pest ovisacs (0, 1, 4, 7, 10 and 13) and each treatment with 8 replications and in the second year, five treatments (0, 5, 10, 15 and 20), each treatment with 7 replications on the leaves were evaluated in a completely randomized design (CRD). Economic injury level (EIL) was calculated as 133, 125, 110 and 131 ovisacs per branches with an average number of 7. 1, 6. 7, 5. 9 and 7 fruits for the first generation of 2011 and 242, 228, 201, and 238 ovi sacs per branches with an average number 7. 1, 6. 68, 5. 88 and 7. 01 fruits for the first generation of 2012, as well as 203, 191, 168 and 200 ovisacs per branches with an average number 7. 1, 6. 68, 5. 88 and 7. 01 fruits for the second generation of 2012, for ethion, chlorpyrifos, buprofezin and diazinon pesticides, respectively.

Background and Objectives: Tristeza is one of the most important viral diseases in CITRUS products worldwide. Fars province is one the most important CITRUS growing regions in Iran. Infection to CITRUS tristeza virus (CTV) has been reported from many CITRUS ORCHARDS in this region. The objectives of this research were to determine CTV distribution, evaluation of CITRUS species infection to CTV and to compare the infection prevalence rate to CTV in different regions of Fars province.Material and methods: This cross sectional study was performed on 230 samples collected from different CITRUS species grown in Kazeroun, Firouzabad, Ghir-o-Karzin, Jahrom, Darab and Fasa regions. First existence of infection to Tristeza virus was detected using ELISA. The prevalence of infection was calculated based on the rate of infection in the total numbers of samples. Next, a PCR amplification was performed based on the primers specific for coat protein and p23 genes.Results: Based on the ELISA test, all CITRUS species were infected to CTV. The virus infection was detected in all the regions of interest. Totally, 24.35% out of 230 collected samples were infected to CTV. The highest infection prevalence was found in Jahrom, Ghir-o-Karzin, D arab , Kazeroun, Firouzabad and Fasa, respectively. Furthermore, mandarin was found the most infected fruit between all CITRUS family, followed by lemon Lesbon, lime, orange and sweet lime, respectively.Conclusion: The results of this research showed that CTV infection has increased during the past years. As a result, control ofthe disease in this region is necessary.

In order to investigate the effect of different summer cover crops on weed dynamics, an experiment was carried out based on Randomized Complete Blocks Design with 7 treatments and 3 replications. The experiment was performed at Islamic Azad University of Amol (Komdarreh region) during 2009. Treatments included white bean (Phaseolus vulgaris), red bean (Phaseolus vulgaris), cow pea (Phaseolus vulgaris), pinto bean (Phaseolus vulgaris), mung bean (Vigna radiate), lentil (Lens culinaris), and common pea (Cicer arietinum). Some cover crop and weed parameters such as dry weight of grass and broadleaf weeds in each plot as well as dry weight of cover crops were determined. A cover crop/weed biomass ratio (CCW Index) was applied to determine the efficiency of different cover crops in terms of weed depression. Accordingly, weed growth in cowpea and mung bean plots was greatly reduced (CCWI=10.25 and 4.13, respectively) and lentil could not compete with weeds (CCWI=0.14) and weeds were dominated in lentil plots. In first stage three cover crops common pea, cow pea and mung bean had the most leaf area but white bean in second stage had the most leaf area among cover crops. In first and second samplings cow pea had the highest dry weight (37.33 and 322.2 gr.m-2) and the least dry weight belonged to mung bean and lentil in second and first sampling, respectively. There was a negative and exponential fit relationship between weed dry weight and cover crop dry weight.

Objective: Importance of management of gardens weeds is an issue that unfortunately has less been investigated by weeds researchers of country. One of the most important restrictive agents of cultivated surface and producing crops of CITRUS ORCHARDS are weeds.Methods: To achieve this purpose, a research was performed in plot of Valencia orange trees of CITRUS fruits of Dezful in 2013. This project was done in the form of randomized complete block with 16 treatments in 3 repetitions. The treatments were mechanical control, Weedmaster herbicide, glyphosate herbicide, vigna unguiculata, vigna radiate, panicum miliaceum L., sorghum bicolor (L) moench, vigna unguiculata+ Weedmaster, vigna radiate+ Weedmaster, panicum miliaceum L.+ Weedmaster, sorghum bicolor (L) moench+ Weedmaster, vigna unguiculata+ glyphosate, vigna radiate+ glyphosate, panicum miliaceum L.+ glyphosate, sorghum bicolor (L) moench+ glyphosate and wetness (uncontrolled).Results: Results showed that sorghum bicolor (L) moench and it’s combining with glyphosate and Weedmaster have the highest height, leaf area, and dry weight, and panicum miliaceum L. and its combining with glyphosate and Weedmaster herbicides have the highest density of covering crops. Weeds had the least leaf area in treatments of sorghum bicolor (L) moench, sorghum bicolor (L) moench+ Weedmaster and panicum miliaceum L., panicum miliaceum L.+ Weedmaster, and the least productive dry weight of weeds was in treatments of sorghum bicolor (L) moench, sorghum bicolor (L) moench+ Weedmaster and panicum miliaceum L., panicum miliaceum L.+ Weedmaster, and panicum miliaceum L.+ glyphosate. Also, the highest Index CCW belonged to treatments of sorghum bicolor (L) moench+ Weedmaster.

During 2011-2012 a survey was carried out for identification of Prostigmatic mites of CITRUS ORCHARDS in Guilan Province. In this survey, total of 22 species belonging to 21 genera and 13 families were collected and identified. Among them, 9 genera and 9 species are the first records for Guilan Province fauna and two genera and three species are the first records for Iranian mite fauna that marked with one and two asterisks respectively. The list of identified species is as follow: Anystidae: Anystis baccarum Linneaus, 1886; Cunaxidae: Cunaxa papuliphora * Sergeyenko, 2009, Pulaeus martini* Den Heyer, 1980, Coleoscirus buartsus * Den Heyer, 1980, Cheyletidae: Cheletogenes ornatus* Canestrini and Fanzago, 1876, Cheletomimus berlesi * Oudemans, 1904, Hemicheyletia wellsiSummer and Price, 1970; Eriophyidae: Phyllocoptruta oleivora Ashmead, 1879; Caligonellidae: Caligonella humilis * Koch, 1838; Camerobiidae: Tycherobius sahragardi ** Khanjani et al., 2012; Raphignathidae: Raphignathus hecmatanaensis Khanjani and Ueckermann, 2003; Stigmaeidae: Eustigmaeus anauniensis * Canestrini, 1889, Eustigmaeus segnis * Koch, 1836, Ledermuelleriopsis plumosa* Willamann, 1950, Storchia rubusta Berlese, 1885; Neopygmephoridae: Pseudopygmephorus pappi** Mahunka, 1976; Tenuipalpidae: Brevipalpus obovatus Donnadieu, 1875; Tetranychidae: Panonychus citri McGregor, 1916, Tetranychus urticae Koch, 1836; Tydeidae: Tydeus meshkinensis* Andre et al., 2010, Brachytydeus mali ** Oudemans, 1929; Trombidiidae: Allothrombium pulvinumEwing, 1917.

CITRUS blast caused by Pseudomonas spp. is one of the most important diseases in the northern CITRUS growing provinces of Iran which causes considerable losses to CITRUS ORCHARDS in conducive climatic conditions. In this study, we tried to isolate and introduce some yeast strains from CITRUS ORCHARDS with acceptable biological control potential against the disease. The evaluations were performed under green house conditions on sour orange seedlings. Yeast cell suspensions were sprayed three times with two-days intervals on seedlings before pathogen inoculation. Statistical analysis of the results was carried out using Randomized Complete Block experimental design and comparison of disease severity means was performed by Duncan's Multiple Range Test. For the identification of the effective yeast strains, ITS regions of their rRNA operon were amplified using universal primers (ITS1 and ITS4) by PCR and the amplified fragments were sequenced. Based on the above procedures and comparison of the sequences with those deposited in the GenBank, the effective yeasts were identified as Sporobolomyces ruberrimus, Cryptococcus albidus, C. magnus and Rhodotorula sp. According to the results, S. ruberrimus, was the most effective yeast and controlled the disease more efficiently than other species.

Increase in cetrus damage by Pulvinaria aurantii in recent years and more pressure of pesticides application by farmer are two urgent problems of CITRUS production in north of Iran. To apply pesticides in a right time that is a component of integrated pest management (IPM), seasonal changes of CITRUS soft scale, Pulvinaria aurantii (Cockerell) densities was studied in central and eastern part of Mazandaran province from 2007 to 2009. There wene two annual generations per year. The first, designated as the summer generation, appeared from June to September, and the second, designated as the autumn generation, appeared from September to the following June. The maximum population of crawlers and first instar of second generation were seen during the last 10 days of june and for first generation during the late of September and beginning of October which is the best time for controlling the pest. Parameter b of Taylor's power low is an index of dispersion that in ordinary population was 9.4, suggested an aggregated dispersion pattern on one tree, however in high population (b=1.57) it became close to random. There was no significant difference between the number of P. aurantii in different geographical direction and inside canopy of the tree in comparison with outside the tree canopy. However, in orchard with no suitable pruning, alwaysP. aurantii population was high. Furthermore, the enough spaw between trees and pruning, cause to decrease infestation by the pest from 25.1% to 8.3%.