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    Pear rust

    The disease is caused by the fungus Gymnosporangium sabinae (or G. fuscum) and is common in Europe and other regions around the world. The disease is easy to be recognized by the bright orange-reddish spots appearing on pear leaves during the summer.

    The fungus has a complex biological cycle as it requires a metabolically active host continuously to survive. Alternative hosts apart from pear (Pyrus calleryana – decorative pear; Pyrus communis – common pear) can be decorative or forest trees of the genus Juniperus. The latter ones are conifers and evergreen and therefore can nourish the fungus during the winter.

    In the autumn, fungal spores (aeciospores) that are produced in special formations on the bottom surface of pear leaves disperse and infect young Juniper stems. Early Summer the reverse phenomenon is observed: Basidiospores, produced in special formations on Juniper stems infect neighboring pear trees.

    Symptoms

    Symptoms on pear trees appear in the spring as yellow-orange spots of 1-2mm in diameter on the upper leaf surface while young stems and fruit can also be infected. Leaf spots extend gradually and get a bright orange – reddish color. Small black dots (pycnidia) appear in the center of the spots by mid-summer. Towards the end of summer, brown bumps are formed on the lower leaf side just below the upper spots and conical protrusions develop (aecidia) in which aeciospores are produced. The aeciospores are released, dispersed by the wind and eventually infect young stems of Juniper trees.

    Importance and control

    Usually overall damage from the fungus is not so severe as to threaten the tree health. Of course, pear production can be significantly affected especially when infection of leaves and young fruits is extensive which can cause defoliation, reduction of photosynsyntic capacity, weakening of trees and yield reduction.

    Usually there is no need for special control measures. Sprays with protective or systemic fungicides (dithiocarbamates, triazoles and/or strobilurins) that are made for pear scab also keep pear rust at tolerable levels.

    Author/photos: Aris Chloridis

    Cotton bollworm (or Corn earworm or African bollworm)

    It is the caterpillar of a moth, which is the fear of cotton farmers in Greece due to the extensive damages it causes to squares, flowers and bolls of cotton and due to its difficult control. The scientific name of the pest is Helicoverpa armigera (or Heliothis armigera) and is one of the most destructive insect pests of cotton, tomato, okra, pepper, tobacco, corn and others.

    The insect has 3-4 generations a year depending on the climatic conditions of the area and develops large populations from July to September, usually with a culmination in August when it causes the biggest damage to cotton. Fortunately, after a number of years with large populations and subsequent severe infestations, 2019 was a year of minor damage by cotton bollworm.

    One caterpillar is not limited to a cotton boll or fruit of another plant. It can infest many organs or many fruits within a few days by eating them superficially and then moving to others, thereby multiplying the quantitative and qualitative degradation of production. Caterpillars rarely cause leaf erosion. Usually infestations are on the reproductive organs (flowers and fruits).

    In general, the difficulty of insect control in cotton, especially in August, is due to the following factors:

    – Bollworm population structure in August (the most destructive generation in cotton) is mixed with all stages present: eggs, caterpillars, pupae and adults. It is therefore difficult for any insecticidal treatment to focus on the most sensitive stage of egg hatching and young caterpillar

    – In August, cotton plants are tall and cotton rows are closed so insecticide spray (with a horizontal bar) does not reach and cover the lower foliage of a cotton plantation

    – Insecticides used today act mainly through stomach and secondarily through contact, so caterpillars that feed and live on the lower layers of cotton foliage are not properly exposed to the insecticide

    Author/photos: Aris Chloridis

    Blossom End Rot (BER)

    A physiological disorder of a plant during the stage of fruit development and growth. It is a quite common problem on tomato, pepper, eggplant and zucchini which is caused by the (usually transitory) low calcium concentration in fruits. The disorder appears most commonly in cases where watering is irregular or in periods of drought and plant stress which induce the transitory decline in calcium absorption and movement in the plant.

    Calcium deficiency can also appear during fruit development due to excessive fertilization with nitrogen and high temperatures which favor fast development of plants, high salinity and root damage during soil cultivation.

    Most of the times BER appears on the first tomatoes of the season as plants under stress at fruit set of the first inflorescence. Usually the problem disappears later in the season, on tomatoes of subsequent inflorescences.

    How you can avoid BER

    – Select varieties tolerant to the disorder
    – Water plants adequately and regularly
    – Mulch plants so that water evaporation from soil in minimized
    – Keep soil pH between 6.5 and 6.8
    – Use fertilizers poor in nitrogen and rich in phosphorus
    – Add calcium to the soil at planting, but only if calcium deficiency is proven. Usually calcium level is adequate in soil but it cannot reach fruits for the reasons explained above
    – Spray foliarly with a calcium fertilizer

    Author/Photos: Aris Chloridis

    Zion®: Ionic Zinc

    The role of zinc in plants

    • Zinc plays an important role in regulation of plant growth, enzyme activation, gene expression, activity of plant hormones, protein synthesis, chlorophyll synthesis and photosynthesis, carbohydrate metabolism, plant fertility, seed and fruit production and defense against diseases
    • It is also necessary in plants for the production of growth hormones and the elongation of internodes.
    • It is a structural component of chemical transmitters and metalloenzymes which regulate plant metabolism and the synthesis of carbohydrates, lipids, proteins and nucleic acids
    • Finally, it is important in the structural and functional integrity of cell membranes
    • A possible zinc deficiency can slow down or inhibit all processes above and eventually weaken health and reduce productivity of plants
    • Highly demanding crops for zinc are maize, alfalfa, citrus, alfalfa, stone fruits, vine, olive, kiwi and other
    • Zinc deficiency is very common in modern crops. It usually occurs in alkaline and calcareous soils with high PH, in calcareous soils with medium or high content in organic matter, in sandy soils as well as in soils produced from rock poor in zinc
    • Zink deficiency usually manifests with pale green, yellow or white discoloration between leaf nerves which starts from new and middle leaves, with plant dwarfism and deformation of leaves and fruits
    • However, in many cases of marginal zinc deficiency, the quality and quantity of production may be reduced without apparent symptoms. For example, in cereals marginal deficiency causes small zinc concentration in grains and reduced nutritional value.
    • Almost half of the world’s soils suffer from zinc deficiency, while this nutrient has been identified as the most critical and deficient for plants, causing serious production losses. As a result, the interest for zinc fertilization has increased greatly in the last decade

    What is Zion?

    • Zion is a liquid fertilizer used against zinc deficiency, with strong acid reaction, which contains concentrated zinc sulphate mono-hydrate (ZnSO4-H2O) in an ionic form with high bioavailability and efficacy
    • Zion content in Zinc is 9.4% w/v, or 9.4 grams of elemental zinc in 100 ml Zion
    • Zion can be applied to crops throughout the vegetative period at very small doses: 1) foliarly at 50-100ml/100L of water and 2) through drip irrigation systems at 1-2L / ha
    • Application doses of Zion vary depending on the crop, size and age of plants, application equipment and crop training system
    • Zion is fully water soluble without any mixing issues in spray or in liquid fertilizer tanks. It reduces the pH of the spray solution thus facilitating the mixing of other active substances that “prefer” acidic pH conditions
    • It is compatible with most agro-chemical products. It is not compatible with unstable products in mixtures such as fosetyl-Al and chlorpyrifos

    Mangan-ion®: Ionic Manganese

    The role of manganese in plants

    • Manganese plays an important role in the production of amino acids and proteins, in lignin synthesis, in the activation of many enzymes (more than 35), in regulating the level of plant hormones, in respiration and in nitrogen metabolism, in the reduction of nitrates and their use by plants, in the formation of chlorophyll and in photosynthesis.
    • A deficiency of manganese may adversely affect the volume of plant crown and the size and color of fruits
    • After iron which is needed in plants at a quantity of 100mg iron / kg dry plant matter, manganese is the next trace element in terms of necessity for plants with a quantity of 50mg Manganese/ kg of dry matter
    • Manganese Mn2+ is easily converted to Mn3+ or Mn4+ and therefore it plays an important role in plants in redox processes, such as photosynthesis, as an electron transport system. Possible deficiency may adversely affect the total volume of plant crown, the size and color of fruits and the total volume of production
    • Deficiency of manganese is quite common and widespread in Greek soil conditions, to a level almost similar to iron deficiency. However, it often goes unnoticed or underestimated by farmers. It usually occurs in alkaline and calcareous soils with a high pH (over 6.5) and with poor aeration, in calcareous soils with medium or high organic matter content, in sandy soils as well as in soils resulting from parental rock poor in manganese
    • Manganese deficiency often appears together with that of zinc or iron due to the similar soil conditions that favor deficiency of these three important nutrients
    • Manganese is an extremely immobile element in plants and therefore symptoms of its deficiency appear first on young leaves in the form of interveinal chlorosis which can be confused with that of iron. However, iron deficiency causes a distinctly more acute and evident contrast between the green nerves and the chlorotic areas while that of manganese is more diffuse and confusing. Also, the symptoms of manganese deficiency resemble those of magnesium with the difference that in the latter symptoms appear on older leaves

    What is Mangan-ion?

    • Mangan-ion is a liquid fertilizer with strong acid reaction, containing concentrated mono-hydrate manganese sulfate (MnSOM4-H2O), in a hydrated ionic form of high bioavailability and efficacy, which is used against manganese deficiency
    • The content of Mangan-ion in manganese is 9.1% w/v or 9.1 grams of elemental manganese in 100ml Mangan-ion
    • Mangan-ion can be applied to crops throughout the vegetative period at very small rates: 1) foliarly at 50-100ml/100L of water and 2) through drip irrigation systems at 1-2L / ha
    • Application rates vary depending on the crop, size and age of plants, application equipment and the orchard/crop training system
    • Mangan-ion is a fully water-soluble fertilizer without mixing problems in spray or in liquid fertilizer tanks. It reduces the pH of the spray solution thus facilitating the mixing of other active substances that “prefer” acidic pH conditions
    • It is compatible with most agro-chemical products. It is not compatible with unstable products in mixtures such as fosetyl-Al and chlorpyrifos

    Metal Ionization Technology In Agriculture’s Service

    One of the most important challenges faced by the sector of agriculture throughout the globe (farmers, scientists and agriculture professionals) is the rational use of fertilizers in crops and the adoption of a sustainable cultivation system with a small environmental footprint resulting in low production costs and minimal environmental pollution.

    According to the Association of Fertilizer Producers and Traders (SPEL), Greek fertilizer consumption decreased by 8.7% (to 667,368 tons) during the growing season between July 2016 – June 2017 compared to the previous year and by 24% compared to 2010. This level is the lowest recorded in the last 25 years, which indicates that crops are heavily under-fertilized. The reduction of 2016-2017 was directly related to the overall negative economic status which prevailed in the agricultural sector. According to industry sources, cultivated plants, due to lack of essential nutrients in soil, could not hold fruit in the spring, while they had difficulty to feed them until harvest. (http://worldenergynews.gr/index.php?id=25655)

    On the other hand, the adverse effects of fertilizers on the environment were identified and studied such as the acidification of agricultural soils which gradually degrade, the toxicity to aquatic organisms in natural water deposits due to leaching (e.g. lakes, rivers, etc.), nitrate pollution of groundwater and drinking water due to deep filtration or surface runoff of nitrogen and the contribution to global warming. (Effects of intensive fertilizer use on the human environment, FAO). These serious environmental impacts are mainly due to the use of simple or complex soil applied fertilizers, which are used only by a small to medium percentage by plants. The remaining percentage ends up to groundwater or surface water deposits and remains unused by crops due to leaching or filtration.

    Agrocure aiming at contributing to the reduction of environmental pollution and small bioavailability of fertilizers, developed, registered and launch in the Greek and European market specialized inorganic plant nutrition fertilizers based on metal ions (Fe2+), copper (Cu2+), zinc (Zn2+) and manganese (Mn2+) complexed with sulphate ions (SO42-) and water molecule dipoles. These liquid fertilizers are applied foliarly or through soil and are 100% bioavailable to plants due to the full ionic form of their metals, which is achieved through a specific ionization method.

    It should be stressed that these fertilizers are not mixtures of minerals/nutrients but special ionic metal products containing one metal/nutrient per formulation. With this series of fertilizers, the following can be achieved:

    • Targeted use of only the nutrient or nutrients which are needed by the plants and no any others which are not needed and which will end up polluting the environment
    • Foliar application and fast absorption by plants of the element or elements which are in shortage since nutrients will be available in their ionic form which is the most absorbable by plants
    • The risks of leaching or filtration in the soil is significantly reduced, while in parallel the percentage nutrient absorption by the plants and therefore the fertilizers efficiency will be increased
    • The cost of agricultural production will be reduced as irrational use of nutrients, not needed by plants, will be minimized
    • Organic certification of agricultural products, since all formulations are products of inorganic natural minerals, compatible with EU regulation 2003/2003 and certified as organic

    Soil, leaf tissue and irrigation water analysis for proper nutrition and fertilization of crops

    Crop yields, as well as qualitative characteristics of some plants (i.e. ornamentals) such as attractiveness, appearance, or flower quality are influenced, besides other factors, by rational nutrition. The proper nutrition of plants has a direct relationship with their health. A well-run organism (plant or animal) responds to stress situations (from climate, diseases, insects or other enemies) better than a weakened and poorly-nourished organism.

    Nourishment of plants is accomplished through soil with the help of soil water and other manual or mechanical practices such as soil cultivation for root oxygenation, etc. Mineral nutrients which are essential for plant development and growth are structural components of soil. There are soil types such as clay or organic ones which are in general rich in nutrients and therefore fertile, however soil nutrients are depleted when crop yields are large. This shortage of nutrients can be faced with continuous supply of fertilizers which are natural materials (i.e. manure in organic farming) or chemically manufactured ones (i.e. common chemical fertilizers in conventional farming).

    The question that arises many times is: does my soil have all the nutrients that my crop needs? Or more generally, is my soil so fertile* that my crop will develop and grow properly without any problems?

    Answers to these questions are provided by soil analysis. A prerequisite for precise and meaningful soil analysis is the collection of a representative and homogeneous sample of soil from our farm (instructions will follow in a future article: Soil sampling technique). A complete soil analysis must be done before the installation of permanent crops such as fruit trees, olives, grapevines, asparagus, clover, etc., by examining 3 different soil zones/depths. Also, an appropriate soil analysis must be done before the installation of annual crops (about 1 – 1.5 months before sowing or planting).

    Apart from soil analysis there is another tool/method which helps us to answer to the question above. This tool is leaf tissue analysis with the help of which we can diagnose a nutrition problem during the development and progression of a crop as it requires presence of leaves. It’s kind of an X-ray of the plant’s nutrient condition.

    Leaf tissue analysis is appropriate especially in established permanent crops (fruit trees, olives, grapevines, etc.) in combination with soil analysis. In fact, the leaf tissue analysis is a better approach for nutrition problems because it does not show the quantity of nutrients in soil but what types and quantities of nutrients plants get from the soil. It is also suitable for dynamic and highly productive annual crops such as tomato, cucumber etc. during their development stage.

    As mentioned above, soil nutrients feed plants with the help of water which is supplied naturally or artificially to the soil. Therefore, the quality of irrigation water (from superficial or deeper agricultural boreholes) is vital for the health of the soil/plant system and quite frequently it creates additional problems.

    High salinity of irrigation water, or presence of sodium, chlorine or boron may create pathogenicity (salination or alkalization) in the soil or toxicity (i.e. from chlorine or boron) in plants. Poor growth of plants, or symptoms of fruit or blossom drop, peripheral burning of leaves, etc. can be caused by poor water quality.

    Consequently, with the help of soil, leaf tissue and irrigation water analyses the benefits for our crops can be multiple:

    1. Selection of the appropriate crop for our soil
    2. Appropriate and balanced fertilization – nutrition of plants
    3. Avoidance of unnecessary costs
    4. Immediate correction of nutrition problems with the help of leaf tissue analysis
    5. Early diagnosis and correction of problems with irrigation water

     

    * The term fertile apart from the adequacy of soil nutrients also refers to the physical condition of soil, that is to parameters such as soil texture and structure, pH (acidic – alkaline reaction), salinity, CaCO3 content, organic matter content, pathogenicity level, etc.

    Author: Dimitris Megas (Laboratory of soil, leaf and water analysis)

    http://www.megalabo.gr

    Essential nutrients for plants

    Plants, similarly to all organisms, need a variety of chemical elements / mineral nutrients to fulfil their metabolic processes. The big trees we all admire, acquire their impressive size and beautiful shape after a series of development and growth cycles during which they absorb carbon (C), oxygen (O), hydrogen (Η), nitrogen (Ν), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulphur (S), iron (Fe), Zinc (Zn), copper (Cu), boron (B), manganese (Mn), nickel (Ni), chlorine (Cl), molybdenum (Mo) and silica (Si) from atmosphere or soil. With all these elements, they compose a big variety of structural and metabolic compounds (sugars, hydrocarbons, amino acids, proteins, lipids, oils and other complex molecules) in order to construct their cells and tissues and to regulate their metabolic processes.

    Three chemical elements, carbon, hydrogen and oxygen are acquired from air’s carbon dioxide (CO2) and from soil water (Η20). When chlorophyll in the leaves is exposed to light these three elements are combined through the process of photosynthesis to compose hydrocarbons and subsequently other more complex substances. For these 3 elements there is no need for additional supply to plants (fertilization) except for cases where the surrounding environment is poor in CO2, which is the case in aquarium plants for example.

    Out of the 18 elements above, nitrogen, phosphorus and potassium are called primary nutrients or macronutrients because plants need them in relatively large amounts while in parallel their shortage is quite common in crops of high productive potential. Their shortage affects production quality and quantity seriously. For this reason, they are supplied to crops frequently and regularly in the form of synthetic or natural, inorganic or organic fertilizers. The type and quantity of fertilizers that are supplied depends on soil type and characteristics, crop/plant species, age of the crop, size and stage of crop etc.

    Calcium, magnesium and sulphur are called secondary nutrients. These are also required by plants at large amounts but it is less likely that they limit plant growth and development because of their abundance in soil. Calcium and magnesium are added through calcareous materials when soil needs pH correction while sulphur is added continuously to the soil with rain water and by its gradual release from the soil organic matter.

    The remaining 9 nutrients are also essential for plant growth but in relatively small quantities in comparison to the elements above. For this reason, they are called micronutrients. These are iron, zinc, manganese, copper, boron, nickel, chlorine, molybdenum and silica. We should not be fooled by the fact that micronutrients are needed in small quantities by plants. They are also vital for plants and their shortage will have negative impact in plant growth and development. It must be stressed that silica in not necessary for all plants while some plants also need sodium (Na) and cobalt (Co). The mean concentration of the various nutrients in the dry matter of a whole plant is shown in table 1 below.

    There is a vast variety of fertilizers available in the market which are supplied to plants when needed either through the soil (by manual or mechanical distribution or by fertigation via the irrigation water) or by spraying them to the foliage. Selection of the appropriate fertilizer(s) for balanced nutrition of plants is a vital and relatively difficult decision which requires knowledge of three important parameters, the properties of our soil, the requirements of our plants or crops in their various stages and the properties of the fertilizer(s) which are going to be used. All these details as well as the importance and role of each nutrient in plants are going to be analyzed in following articles in our site.

    Table 1. Mean concentration of 17 elements in whole plant dry matter, which is considered adequate for normal plant development and growth (Epstein & Bloom, 2005)

    Element mg/kg (ppm) % w/w Relative number of atoms needed by plants
    Nickel 0.05 1
    Molybdenum 0.1 1
    Cobalt 0.1 2
    Copper 6 100
    Zinc 20 300
    Sodium 10 400
    Manganese 50 1000
    Iron 100 2000
    Boron 20 2000
    Chlorine 100 3000
    Silica 0.1 30000
    Sulphur 0.1 30000
    Phosphorus 0.2 60000
    Magnesium 0.2 80000
    Calcium 0.5 125000
    Potassium 1 250000
    Nitrogen 1.5 1000000

    Sources for further information:

    Epstein E and Bloom AJ (2005). Mineral Nutrition of Plants: Principles and Perspectives, 2nd edn. Sunderland, MA: Sinauer

    Forth, HD (1990). Fundamentals of soil science, 8th edn. John Wiley and Sons

    Marschner H (1997). Mineral Nutrition of Higher Plants. Academic Press, London

    Miller AJ (July 2014). Plant mineral nutrition, https://www.researchgate.net/publication/300178484

    Sonneveld C and Voogt W (2009). Plant Nutrition of Greenhouse Crops, Springer