The Studies On Active Fractions Of Pesticidal Plants In Killing Nauplius Of Lernaea Ctenopharyngodontis

In order to find out some novel pesticidal plants to kill parasites in fish, we have tried 18 kinds of pesticidal plants in toxicity tests to nauplius of Lernaea ctenopharyngodontis (NLC). Comparing the results of acute toxicity tests, especially mortality, has screened some effective active fractions of pesticidal plants.The studies included three parts. The first part of study was aimed to clarify the effect of some environmental factors on hatching rate and survival rate of NLC. The killing ability to NLC of some crude extractive fractions from pesticide plants were tested in the second part of the study. Tests of four effective botanical pesticides on killing NLC were conducted in the third part of the study.The first part of study consists of 5 trials, that is, 1) study of the effect of different time in vitro culture on hatching rate of NLC' egg cell; 2) study of the effect of water temperature on hatching rate of NLC' egg cell; 3) study of the effect of water temperature on survival rate of NLC; 4) study of the effect of culture water from different resources on survival rate of NLC and 5) study of the effect of pH on survival rate of NLC.18 kinds of crude extractive fractions from pesticidal plants were prepared in using different kinds of extraction solvents and different kinds of extraction methods in the second part of study. Commercial drugs were used in acute toxicity tests to kill NLC under the same condition as control. By comparing mortality some kinds of botanical pesticides had been screened.In the third part of study, different fractions of four kinds of effective pesticidal plants were extracted. Under the same condition, different fraction extractives and crude extractive fractions had been used in acute toxicity tests to kill NLC to compare their efficacy.The results are shown as follows:1. (25+1)C is a suitable hatch temperature for green eggs of adult Lernaea ctenopharyngodontis , 48 hours after lying. Higher hatching rate could be also be achieved when water temperature was about (25+1)C. Distilled water could ensure high survival rate in water temperature of (25+1) C and pH 7.5 can be a favorable pH for hatching.2. 18 kinds of selected pesticidal plants were extracted from pesticidal plants from different producing areas, using 75.0% alcohol and water as extractive solvent andcertain extracting modes. Results of acute toxicity tests from crude extractive fractions of 18 kinds of selected pesticidal plants on NLC were got. Cortex Meliae > Radix sophorae flavescentis Herba Macleayae Cordatae .. Herba Agrimoniae, whose killing abilities to NLC were higher than 90.0% whose adjusted mortality were higher than 85.0%, were screened out.3. The efficacy of four kinds of pesticidal plants in killing NLC were as follows: The efficacy of water soluble fraction of Cortex Meliae was higher than other extractives of Cortex Meliae in the 24h acute toxicity test. The efficacy of matrine was higher than that of crude extractive fraction of Radix sophorae flavescentis in the acute toxicity test. The effect of crude extractive fraction of Herba Macleayae Cordatae was higher than that of bocconoline in the acute toxicity test. The effect of alcohol soluble fraction of Herba Agrimoniae was higher than that of other extractives of Herba Agrimoniae in the 48h acute toxicity test. The results of which can be showed like this: crude extractive fraction of Cortex Meliae < crude extractive fraction of Herba Macleayae Cordatae< crude extractive fraction of Herba Agrimoniae< crude extractive fraction of Radix sophorae flavescentis.