Identification of Plant Physiological Disorders: Diagnosis of Diseases Caused by Abiotic Pathogens
Identification of Plant Abiotic Pathogens and the Diseases They Cause (Physiological Disorders)? During the process of plant growth and development, unsuitable physical factors, chemical factors, air pollution, pesticide toxicity, as well as the plant's own physiological defects or hereditary diseases in the environment, will all cause plants to develop diseases caused by abiotic pathogens. Such diseases have no infection process and cannot be transmitted to one another, and are called non-infectious diseases or physiological disorders.
I. Nutritional Imbalance
Nutritional imbalance includes nutrient deficiency, imbalance in the proportions among various nutrients, or nutrient excess; these factors can induce plants to show various disease symptoms. There are several causes of plant nutrient deficiency: first, a lack of nutrient elements in the soil; second, an improper proportion of nutrient elements in the soil, where antagonistic effects among elements affect plant absorption; third, unsuitable soil physical properties, such as temperature that is too low, moisture that is too little, or pH that is too high or too low, all of which affect the plant's absorption of nutrient elements. In fields where large amounts of chemical fertilizers and pesticides are applied, and under conditions such as frequent continuous cropping in protected cultivation, the imbalance between major elements and trace elements in the soil becomes increasingly prominent, and crops growing in such soil environments often show symptoms of nutritional imbalance. Excessively high levels of certain nutrient elements in the soil are also unfavorable to plant growth and development, and can even cause serious damage.
II. Environmental Pollution
Environmental pollution mainly refers to pollution of air, water sources, and soil, as well as acid rain, and so on. These pollutants cause different degrees of harm to different plants and produce varying symptoms.
III. Phytotoxicity
When chemical pesticides are applied to plants, if the type selected is inappropriate, the application method is unreasonable, the application timing is unsuitable, or the application concentration is too high, all of these can cause harm to plants.
Control Methods:
1. Spray water to wash off the pesticide: If phytotoxicity is caused by spraying pesticide solution on leaves and plants, and it is discovered early, before the solution has fully penetrated or been absorbed into the plant body, the affected plants can be quickly sprayed with a large amount of clean water, repeatedly sprayed 3-4 times, to wash off as much of the pesticide on the plant surface as possible. You can also add 0.2% soda ash or 0.5% limewater to the sprayed clean water. Since most pesticides are currently acidic and decompose and lose effectiveness upon encountering alkaline substances, this can accelerate the decomposition of the pesticide.
2. Drainage and irrigation to reduce pesticide residues: For phytotoxicity caused by some poisoned soil and some herbicides, appropriate irrigation and drainage or cross-irrigation with water can wash away the pesticide and reduce toxicity, thereby reducing the severity of the phytotoxicity.
3. Use Zhuangyuanjia at a content of 0.5%, generally diluted 500 times, add 2 liang of white sugar and 2 liang of edible vinegar, mix with 30 jin of water, and spray on the foliage. This has the following effects on crops: immunity, rejuvenation, disease resistance, yield increase, phytotoxicity relief, and frost damage prevention.
IV. Fertilizer Damage
Applying chemical fertilizers at the wrong time or with improper methods often leads to fertilizer damage. Dehydration-type fertilizer damage is caused by applying too much chemical fertilizer at one time, or by insufficient soil moisture after fertilization leading to an excessively high concentration of the fertilizer solution, which causes reverse osmosis of water from crop cells, resulting in dehydration of the crop, mostly manifesting as wilting, resembling frost damage or scalding by boiling water; in mild cases it affects growth and development, and in severe cases the entire plant dies. Scorch-type fertilizer damage occurs when fertilizers such as ammonia water or ammonium bicarbonate are applied at relatively high temperatures, producing large amounts of ammonia gas that harm the crop; in mild cases the lower leaf tips of the plant turn yellow, affecting growth and development, and in severe cases the entire plant dies. Seed-burning fertilizer damage occurs when too much seed fertilizer is applied, or when seeds are dressed with superphosphate, volatile ammonium bicarbonate, urea, calcium cyanamide, and other chemical fertilizers, causing seed burning that can lead to missing seedlings. In addition, when applying foliar fertilizer, using too high a concentration can also cause leaf burn.
Solutions:
1. Watering to reduce damage: In the early stage of fertilizer damage, immediately apply 2 buckets of Peigen with irrigation water to promote the downward leaching of salts, fertilizers, and the like remaining in the soil plow layer, reduce their concentration in the soil spaces, and lower their continued impact on the plant root system.
2. Root irrigation treatment: Use 4 bottles of the biological bacterial agent Peigen plus 1 bottle of Lujian, 2-3 liang per plant, to stimulate root growth, quickly restore plant vigor, and alleviate root burn and seedling burn. In addition, the amino acids contained in it can be quickly absorbed and utilized by the roots, alleviating the nutrient deficiency of the plant root system caused by root burn and strengthening plant vigor.
V. Imbalance in Water Supply
When plants are subjected to a long-term insufficient water supply, vegetative growth is inhibited, the volume of various organs decreases, quality decreases and deteriorates, resulting in short and slender plants. When water is severely lacking, symptoms such as plant wilting and scorched leaf margins can occur, causing leaf drop, flower drop, and fruit drop, and even the entire plant withering and dying.
Too much soil moisture can affect the rise of soil temperature and soil aeration, weakening plant root activity or even causing toxicity, leading to root rot, slow plant growth, yellowing and drooping of lower leaves, flower and fruit drop, and in severe cases causing plant death. When water supply is uneven or changes drastically, it can cause cracking of root vegetables, cabbage, and tomato fruits, or cause cucumbers to form deformed fruits and tomatoes to develop blossom-end rot.
VI. Temperature Too High or Too Low
High temperatures can rapidly weaken photosynthesis, enhance respiration, reduce carbohydrate accumulation, and slow growth, sometimes causing plant dwarfing and premature maturation. When the temperature is too high, it often causes scorching of plant tissues such as stems, leaves, and fruits. In protected cultivation, if ventilation and heat dissipation are not timely, high-temperature damage is also often caused. High temperature and drought often cause large amounts of leaf drop, flower drop, and fruit drop in peppers.
Low temperatures are also very harmful to plants. Diseases caused by low temperatures above 0°C are called chilling injury. Some warm-loving plants, as well as tropical, subtropical, and protected-cultivation plants, are susceptible to chilling injury. When the temperature is below 10°C, common chilling injury symptoms such as discoloration, necrosis, and surface spots appear, and on woody plants, bud blight and top blight appear. If plants encounter a relatively long period of low temperature during the flowering stage, it will also affect fruit set. Plant diseases caused by low temperatures below 0°C are called freezing injury, mainly manifesting as water-soaked dark brown lesions on young stems or young leaves, after which the tissue gradually dies, and in severe cases the entire plant turns black, dries up, and dies. Soil temperature that is too low often leads to poor root growth of seedlings, causing crops such as cucurbits to suffer from seedling “root drowning (root irrigation with Peigen diluted 300 times + Lujian diluted 300 times works well)”, making them susceptible to infection by rhizosphere pathogens.
The effect of drastic temperature changes on plants is often greater than that of simple high temperature or low temperature. For example, if the diurnal temperature difference is too large, it can cause scorching or frost cracking of the branches and trunks of woody plants, and this symptom is commonly seen on the sunny side of tree trunks.
VII. Unsuitable Light
Insufficient light usually leads to leggy growth in plants, affects chlorophyll formation and photosynthesis, causes plant yellowing, makes plant tissues fragile, and makes them prone to lodging and infection by pathogens.
The Zhongtian brand new energy-saving plant growth lamp emits special wavelength light and is composed of four colors: red, yellow, blue, and green. These lights are exactly suitable for absorption during plant photosynthesis. This plant growth lamp adopts mature energy-saving lamp technology, and a large number of experimental results prove that, under the condition of ensuring temperature in a greenhouse, it can promote plant photosynthesis and achieve the goal of increasing yield and income, so the energy-saving plant growth lamp is an indispensable supplementary lighting device in off-season cultivation.
Excessively strong light often combines with high temperature and drought, causing sunscald and leaf scorch.
Unsuitable light duration can also delay or advance the flowering and fruiting of long-day plants or short-day plants, and can even cause plants to fail to flower and fruit, causing serious losses to production.
Non-infectious diseases often cause plant growth to weaken and disease resistance to decrease, and are also a cause of inducing infectious diseases. Infectious diseases occur because plants are infected by pathogens, thereby reducing the plant's stress resistance; when the environment changes drastically, non-infectious diseases are also prone to occur.