Effects of pesticides adhesive work on reducing pesticide application to controlling Grapholita molesta (Lepidoptera, Tortricidae)

Abstract:【Objective】As the current pesticide preparation screening process was tedious large amount of pesticide application was environmentally disastrous, and the dilution rate was not clear, , a method was proposed to combine adhesion work and its adhesion curve of beta-cyfluthrin EW at different dilu- tion rates with surface free energy of fruit tree leaves and data of field efficacy trials, in order to directly screen out the best pesticide and applying rates. This study would establish a way for rapidly screening pesticide indoors and spraying at reasonable concentrations, which could provide a theoretical basis for proper application of pesticide, to accomplish chemical reduction and efficiency improvement.【Meth- ods】The veined sections of the fresh apple leaves were removed, then they were cut into strips of 0.5 cm × 5.0 cm, sticking to the slide with double-sided tape. The slides were placed on the sample surface of the contact angle measuring device, three syringes prepared in advance were used to absorb deion- ized water, ethylene glycol and DMF, respectively, and then they were settled on the contact angle mea- suring device successively, 10 drops were dripped to the abaxial and adaxial surfaces of the leaves, to study the contact angle of abaxial and adaxial surfaces for three standard reagent of deionized water, eth- ylene glycol and DMF on apple leaves, by using optical contact angle measuring device to analyze the droplet profile, and using OWRK method to count surface free energy of leaves. The surface free ener- gy combined with surface tension of different Beta-cyfluthrin EW was measured, by using optical con- tact angle measuring device SCA22 software to calculate adhesion work and its contour curve of differ- ent beta-cyfluthrin EW dilutions on apple leaf surface. The field pharmacodynamic test was carried out for Grapholita molesta at Jinzhong city, Shanxi province. Three concentration gradients were set for each agentia, and total treatments were 12, with clear water as the control. A total of 13 test groups were designed, and a protection line was set for each treatment with 3 replicates in random blocks.【Results】The adhesive work of each agent on the adaxial surfaces of apple leaves was greater than that on the ab- axial surfaces, as for the same agent, the adhesion work gradually added with the increase of dilution ra- tio on both adaxial and abaxial surfaces. For different agents, the difference in adhesion work was small at the same dilution ratio, and the difference in emulsifier combination had little effect on adhesion work. The adhesion work was the interaction force between the agent diluent and the target foliage, this effect can be an intermolecular force, or a combination of different bonds, and it can be a long - term stable mechanical action at a microscopic interface. The greater the adhesion work, the closer the binding between the liquid and the target, and it stuck to the leaves easier. The contour of adhesion work was based on the contact angle and the agent on the target leaf surface, and the adhesion work curve of the agent on the leaf surface was drawn accordingly, and the adhesion effect of the medicinal solution on the leaf surface was studied from the following two aspects: wetting and adhesion. The study on ad- hesion work and adhesion curve showed that on adaxial and abaxial surfaces of the apple leaves, when third beta-cyfluthrin EW was closest to the optimum line, the adhesive effect was best. Verifying tests in the field showed that third beta-cyfluthrin EW controlling effect was best, at a dilution of 2 000 and 3 000 times, and the efficacy of third beta-cyfluthrin EW was 97.00% and 98.50%, respectively, fol- lowed by the second ones, the efficacy was about 90.00%. The effect with first control was the worst, the highest control effect was 84.93%, and the lowest control effect was only 71.47%.【Conclusion】The dispersive force component was the main component on the adaxial and abaxial surfaces of the ap- ple leaves. According to the different periods of different crops, the leaf surface properties are quite dif- ferent, further trial is required, the mechanism to the effects of different components in the liquid, the content of the components of the crop leaves, and the microstructure of the waxy layer on the adhesion work of will need to be studied, so as to improve screening of liquid by adhesion work and determination of optimal concentration. Combined surface free energy of apple leaves with the surface tension of the liquid, adhesion work and adhesion work curves, the effect of prevention and control to Grapholita molesta could be better revealed. It was recommended that the beta-cyfluthrin EW should be diluted to 3 000 times with no. 3 agent for the control of Grapholita molesta, and the best agent and its applied concentration can be screened by experiments indoors with the aid of adhesion work, so as to reduce the number of field trials, extend into field applications, save large amount of manpower and materials, and improve the efficiency. It is of great significance to reduce pesticide application and increase control ef- ficacy in orchards, delaying the occurrence of drug resistance and protecting the ecological environment.