To understand the current situation and laws of pests and diseases, the only way is to go to the field to investigate or monitor.
1. Purpose and method of monitoring
Whatever you do, there is purpose. The purpose is different, and the method will be very different. Accordingly, it is possible to roughly distinguish between pest and disease monitoring into the following two types.
One is a productive survey. The purpose is to understand the extent and extent of the occurrence and damage of pests and diseases in the production field to guide prevention and control. Such surveys should be selected during the period of the appropriate or probable period of the control of the pests and diseases, or the key growth period of crop formation; surveys often use attribute sampling or sampling, focusing on a wide range of censuses and classified surveys, rather than requiring accurate. Often only check the number of pests and the degree of damage. It is often represented by the type of pests and diseases, the rate of disease (worm), the rate of disease (worm), and the rate of diseased plants (the rate of insects).
The other is to grasp the dynamics and laws of pests and diseases, and ultimately serve the monitoring of forecasting and prevention strategies. To this end, it is necessary to continuously perform systematic investigations of timing, fixed point, and quantitative. Such surveys are more suitable for the use of the term “monitoring†to observe a dynamic process. On the one hand, the normative nature of survey methods and data is emphasized so that they can be accumulated and compared with each other for a long time. On the other hand, such observations may be directed to the entire pest and disease system. Although the survey is based on pests and diseases, it is also necessary to comprehensively observe the relevant meteorology. Factors, cultivation conditions and crop growth conditions in order to establish a reliable predictive model.
2. Basic requirements for monitoring
2.1, representativeness and accuracy
One of the purposes of the survey is to use some numerical values ​​to represent the actual situation, or to obtain relatively reliable representative values ​​through sample surveys and mathematical statistics. They have a certain error compared with the actual occurrence (true value), and the opposite of the error is the accuracy. To improve the accuracy of monitoring, we must pay attention to the sampling method (see the second lecture), the number of samples and continuously improve their ability to observe and judge.
2.2, Comparability and Standardization
The results of multiple or multiple surveys should be compared, and multiple comparisons can be used to make evaluations and find patterns. Therefore, standardization of survey methods is one of the guarantees for the quality of pests and diseases. To this end, the state and the department have developed a series of "norms" that must be observed.
2.3, integrity
Since the development of pests and diseases is affected by many factors, it is necessary to grasp the relevant situation as much as possible in order to make predictions. When investigating pests and diseases, we must pay attention to the environment in which they are located, including meteorology, soil and cultivation management, and also pay attention to their time matching.
2.4, experience and intuitive judgment
Pest monitoring is mostly based on visual observations and instrumental measurements to obtain estimates and measurements. Since plant diseases and insect pests are a biological phenomenon, the pest and disease epidemic involves the complex relationship of the entire ecosystem, so the monitors are required to have certain professional knowledge and intelligence. In the identification of the symptoms of pests and diseases, the assessment of the severity of pests and diseases, the area of ​​pests and diseases, and the extreme value of the selection, the visual judgment of the monitors has a very special significance. To this end, it is necessary to stabilize the reporting team and continuously cultivate and improve its quality.
3. Basic concepts of investigation or system monitoring
3.1, the unit is the standard amount of observation or measurement
Usually refers to individual plants, leaves, flowers, fruits, ears, etc. of crops. According to the needs, it is also possible to determine the field or town, district, county, etc. as the survey unit. Obviously, the survey unit greatly affects the fineness of the survey, but it cannot be too fine. It depends on the specific purpose of the survey, time and manpower.
3.2, the degree of pests and diseases in the unit
For any unit, it is possible to investigate the two states of disease (worm) or disease-free (worm), which are the results of the classification according to the difference in quality. If further subdivided, diseased (insect), the number of individuals or the degree of disease on the different sampling units will vary greatly. To this end, it is also necessary to conduct a graded survey or numerical survey of units with pests and diseases. For example, the number of individual insects often used in pest investigations (equivalent to the pest density in plants). Since plant pathogens are mostly small and are not easy to count, the disease area (or volume) is often expressed as a percentage of the area (or volume) of the survey unit, also called severity. For example, when investigating leaf disease, the severity of the disease area is the total area of ​​the leaf. The actual disease severity is obtained by visual estimation. Because the resolution of the eye is proportional to the geometric progression of severity.
For some diseases (worms) with more complicated symptoms (multi-finger systemic infection), although the severity is still expressed by the numerical value, its level can not be divided according to a simple quantity, according to various morphological indicators. Grade the disease. For example, the grade of disease in a rice sheath blight should be balanced with whether it is dead or the height of the lesion:
Level 0: The whole plant is disease free;
Grade 1: from the parietal lobe to the leaf sheath or leaf disease below the first leaf;
Grade 2: from the sheath or leaf below the first leaf;
Grade 3: incidence of parietal lobe;
Level 4: The whole plant is ill and prematurely dying.
Cotton Verticillium wilt and Fusarium wilt are classified according to the degree of dwarfing of plants, leaf discoloration and degree of wilting.
3.3 Statistics on the extent of occurrence of groups (or a certain area)
Since only a large number of individuals can cause damage to production, it is important to understand the extent of the occurrence of pests and diseases in the group. This requires statistical analysis (mainly averaging) based on individual observations. The rate of insects and the number of individual insects is divided into two categories: insects and insects. The number of insect units counts as a percentage of the total number of survey units; the latter is the average number of insects per unit. The unit of the plant is the amount of insects.
The prevalence rate and the prevalence rate of the disease index represent the prevalence of disease occurrence in the plant population. The unit of observation is divided into two categories: disease and health, and the number of plant units in the disease is calculated as a percentage of the total number of investigation units. The plant unit may be a plant, a leaf, a stem, a fruit, an ear, etc., and the nouns corresponding to the general rate are a diseased plant rate, a diseased leaf rate, a diseased fruit rate, a diseased ear rate, and the like. The disease index combines the prevalence rate with the severity of each unit's condition and uses a numerical value to fully reflect the degree of disease in the plant population, usually expressed as a decimal number of 0--1.
4. Monitoring instruments and new technologies
The general instruments include black light lamps that trap pests, spore collectors that collect pathogens from sticky traps, and more, some environmental monitoring instruments such as self-meter temperature and humidity meters, illuminance meters, anemometers, and rain gauges. Remote sensing technology Remote sensing technology is a comprehensive new detection technology that has been rapidly developed in recent years. It accepts different electromagnetic waves radiated or reflected by the target, and provides a quick and accurate information about the target to be measured through a series of processing and interpretation processes. Because the wavelength of electromagnetic waves used by remote sensing technology can be as small as it is, it can "see" the light that is not visible to the human eye, and because this technology is fast, the area of ​​monitoring is large, the data specification obtained can be directly input into the computer. Other advantages have been widely used in military reconnaissance, weather forecasting, geological exploration, agricultural estimation and other fields, and will have broad application prospects in pest and disease monitoring and prediction. Near-surface remote sensing and aerial remote sensing may be more suitable for disease monitoring, but it is easier to achieve in systemic infective diseases and forest disease monitoring. Computer online system With the rapid development and extensive use of computer science and technology, human beings can fully automate the monitoring, recording, and storage of environmental factors. Even after inputting certain data processing rules and prediction formulas, computers can do Disease prediction. This forms a pest and disease predictor that combines monitoring and prediction. Such as the commercial apple pear scab predicted.
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