Abstract:

Objective: Rhagoletis batava obseuriosa(RBO) is one of the major fruit borers of sea buckthorn. There are some limitations in using attractant or pesticide alone have limitations to control the RBO adults,thus the microsphere techniques were used to embed pesticides and attractants into microspheres in order to attract and kill the RBO adults,and prolong their effectiveness period in the field. Method: Gelatin and polylactic acid were used as the wall materials of microspheres,and spinosad and ammonium carbonate were used as the core materials. The microspheres containing the insecticide and attractant were prepared by the solvent evaporation method. Since ammonium carbonate is water-solubile and spinosad is oil-solubile,a water-in-oil- and then in-water(W1/O/W2) double-emulsion method was used to encapsulate the attractant and the insecticide. A single factor experimental design was adopted by taking different quantities of ammonium carbonate as variable,and polylactic acid,spinosad,gelatin and reaction temperature as fixed value,to evaluate the influence of different ammonium carbonate contents encapsulated in the microspheres on the physical and chemical properties of the microspheres. Infrared spectroscopy was used to detect if spinosad and ammonium carbonate were successfully embedded in the microspheres. The spinosad contents in the microspheres were determined using HPLC(High Performance Liquid Chromatography),and the ammonium carbonate content could be calculated by measured the N content within a sample using the Kjeldahl apparatus. Dialysis bag techniques and HPLC method were used to evaluate the release rates of spinosad from the microspheres. The quantities of ammonia released from the microspheres were evaluated every day by using an ammonia detector. The morphology of the microspheres was checked by the scanning electron microscope. The sizes and the span index were measured using a laser particle size analyzer. The attractiveness and lethal effect of the microspheres on the RBO adults were studied by bioassay. The microspheres were also sprayed in the field by the drone to test their control of the RBO adults. Result: The result of the infrared spectroscopy test showed that both the spinosad and the ammonium carbonate were successfully embedded in the microspheres. With increasing the quantities of ammonium carbonate,the quantities of spinosad and ammonium carbonate encapsulated in the microspheres firstly increasing then decreasing. The release of spinosad from the microspheres was able to last for 15 days,which was longer than the release time by the given same quantity of pure spinosad 7 days. The release of ammonium carbonate from the microspheres could last 14 days,also longer than that by the same quantities of pure ammonium carbonate only 6 days. Therefore,the prepared microspheres could fulfil the objective of prolonging the release period of insecticide and the attractant. The microspheres prepared by the different ammonium carbonate contents were spherical and dispersed,with uniform size,porous surface. The average diameter of microsphere was about 60 μm. There were significant differences (P < 0.05) in the attractiveness and lethal effect between the four kinds of ammonium carbonate content microspheres and the control,indicating that the prepared microspheres had attracting and killing ability to the RBO adults. Compared with the control,the population densities of the RBO decreased by about 76.13%,and the damage rates of the sea buckthorn fruits decreased by about 75.38%. Conclusion: The spinosad and ammonium carbonate have been successfully encapsulated into the microspheres,and both embedded compounds had continuous release effect. The prepared microspheres have the attractive and lethal effect on RBO adults,and could be used for the control of RBO.

Key words: microspheres, Rhagoletis batava obseuriosa, spinosad, ammonium carbonate