How to determine the efficacy of pesticides? The relevant experts of China Pesticide Network have summarized: through indoor virulence determination and inter-forest efficacy test.
Indoor virulence determination Indoor virulence determination is mainly to determine the toxicity, virulence of a drug or to compare the virulence of several drugs. The results of the laboratory test, in addition to being used as a basis for the preliminary screening of the agent, can also provide a reference for the inter-forest test. Sometimes problems found in the forest must be taken back indoors for more detailed experimental research.
In-house tests should pay attention to: 1 The test organisms should be cultivated from the same environment, or collected from the same environment in the forest, the more consistent in physiology and development. 2 The test agent must be pure (crude oil or raw powder), at least with the exact active ingredient content. 3 Test under controlled conditions and apply uniformity. 4 The test generally requires 3-5 repetitions for each treatment, and each treatment requires 50-100 insects (the fungus spores are generally about 100 in the microscope 10×10 field of view, and each slide must be moved to check the slides. 3 times). 5 Various tests must be established. The controls provided were: completely untreated (under natural conditions), a so-called "blank" control; a formulation containing no active ingredient or a clear water control, a control treated with a standard agent.
In determining the virulence of a drug, a series of doses (or concentrations) are generally used to determine the percentage of death for multiple groups of organisms, and then the dose-mortality virulence curve is plotted at different doses and corresponding mortality rates. A line parallel to the abscissa is drawn from the mortality rate of 50% on the ordinate to intersect the curve. The dose (or concentration) there is LD50 (or LC50). However, since this curve is S-shaped, it is not easy to accurately obtain the value of LD50 or LC50, and it is not easy to compare with other curves by using the S-shaped curve. Therefore, it is necessary to change this S-shaped curve into a straight line. The common statistical method is to use the logarithm of the dose. The mortality rate is expressed by the probability value, and the S-shaped curve can be changed to a straight line. Often referred to as "dose log-proportional value straight line." Mortality check rate (see Schedule 2 probability and death percentage conversion table). From the slope of this line, the degree of sensitivity of the test organism to the drug is also known, that is, the greater the slope, the smaller the difference between the test organisms; the smaller the slope, the greater the difference. In the indoor virulence test, in the non-medicated control group, a small number of naturally-dead individuals often appear. If the natural mortality rate is below 5%, the mortality of the treatment group is generally corrected by subtracting the natural mortality rate. mortality rate. When the natural mortality rate reaches 5%~20~, the direct subtraction method cannot be used. The corrected mortality rate of the treatment group should be calculated according to the following formula. If the natural mortality rate exceeds 20%, the test organisms should not be used. The test or test should be repeated.
The inter-forest efficacy test mainly tests or compares the efficacy of the agent under inter-forest conditions, and the results are close to the actual situation, providing a reliable basis for production control.
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