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Application Technology of Azadirachtin

1. Application in advance and prevention first

Azadirachtin is a kind of botanical pesticide widely used in the world and generally recognized by the biological control and organic agriculture communities with a use essence of “application in advance and prevention first”. The acting mechanism of azadirachtin is very special and the use of azadirachtin shall follow the principle of “early and small-scale control”. Therefore, a suitable application period shall be selected and the control by pesticide shall be carried out in advance when azadirachtin is used for pest control, i.e. a good control effect can only be achieved by applying the pesticide between the incubation period of pest eggs and the young larvae period. In addition, the azadirachtin has a systematic property and can only work after being touched and absorbed by plants and pests, therefore, the whole parts of a crop shall be sprayed in case of application.

2. Use in the morning and evening, constant spraying and full coverage application

The active ingredients of azadirachtin are unstable under the light and are liable to be decomposed under the sun, so a better control effect can be achieved if the application is carried out in the evening or on cloudy days. In addition, the azadirachtin has a certain deterrent effect on the pests, so it is a kind of protective agent for crops and can only protect the crops well after the leaves of crops and the pests are in full contact with the azadirachtin solution. Therefore, constant spraying is suitable for azadirachtin and shall be uniform with full coverage achieved; If it rains within 24 hours after the application, a supplemental application shall be carried out in time on a fine day.

3. Effect improvement by secondary dilution

During the preparation process, the azadirachtin preparation shall be mixed uniformly with small amount of water first and then poured into the barrel in which the rest of water shall be added and the azadirachtin solution shall be stirred uniformly. Or 1/3 of water shall be added to the barrel first and kept still for 5min after azadirachtin preparation is added and stirred uniformly, and then the rest of water shall be added to the barrel and the azadirachtin solution shall be stirred uniformly for spraying. This method is called “secondary dilution”. The azadirachtin and water are mixed uniformly in the azadirachtin solution prepared in this method and the control effect is naturally better.

4. Suitable water temperature and water quality

The water temperature is also very important during the preparation process. The water temperature shall be generally about 20℃ in case of application in winter or the cold regions in the northern area of China, especially the facility agriculture region. If the preparation temperature is below 20℃, the applying effect of azadirachtin will be affected. For the plants that are difficult to be wetted during the spraying process, the effect can be properly improved by the addition of spreader during the preparation process. The azadirachtin is stable in acidulous to neutral environment and the acid-base property of local water quality shall be measured before application. If the water quality is alkaline or strongly alkaline, the reagent like “add a little” water regulating agent or other products with the function of regulating the pH value of water quality shall be added to regulate the water quality to acidulous to neutral state.

5. Large-scale and continuous use

The azadirachtin has not only antifeedant effect on the larvae, but also strong intervention effect on the growth and development of pests and the actions like oviposition. Therefore, large-scale and continuous application of azadirachtin product in the same forest or crop base has an obvious inhibitory effect on the population density of pests. In the paper Evaluation of the suppressive effect of azadirachtin emulsion on phyllotreta striolata (fabricius) population published by Hou Youming et al., scholars from the College of Plant Protection of Fujian Agriculture and Forestry University, some indexes of life table analysis method are applied to analyze the population suppressive effect of azadirachtin emulsion on phyllotreta striolata (fabricius) and the results show that the significant deterrent effect of azadirachtin on the adults is the main mechanism of population control. 0.50 ml/L azadirachtin has an deterrence rate of 83.75%, decreased population trend index I of 0.3354 and interference index of population control of 0.0863 on the adults; Likewise, in the paper Suppressive effect of azadirachtin emulsion on conopomorpha sinensis bradley population published by Xian Jidong from South China Agricultural University, the test results show that in the processing area where the concentrations of azadirachtin emulsion are 6.0ml/L and 3.0ml/L, the population trend indexes of conopomorpha sinensis bradley are respectively 1.23 and 1.45, which are much lower than that of the control area (11.60) and the interference indexes of population control are respectively 0.106 and 0.112; The suppressive effects of the azadirachtin emulsion of these two concentrations on conopomorpha sinensis bradley population can be respectively up to 89.4% and 87.5%, which fully shows the suppressive effect of azadirachtin on pest population density.

6. Evaluation on control effect of azadirachtin

Azadirachtin is a kind of botanical pesticide and its acting mechanism is different from those of chemical pesticides and common biological pesticides. Therefore, it is a confusing problem for many experts and users to evaluate the control effect of azadirachtin correctly. Currently, the philosophy of crop protection rate put forward by Professor Xu Hanhong from South China Agricultural University is generally accepted. In the papers Application of protection rate as the toxic criterion in evaluating joint action for mixture of insecticides and Application of leaf protection rate to bioassay of insecticides published by Professor Xu Hanhong, how to correctly evaluate the control effect of azadirachtin is stated, which mainly refers to the scientific assessment on the effect of azadirachtin application on preventing the regional crops from being damaged by plant diseases and insect pests. Therefore, different from the generally understood purpose of pesticide application, the real purpose is to prevent the crops from being damaged by plant diseases and insect pests, thus leading to production reduction.