Research On Residue Of Paclobutrazol In Peach And Its Safe Application

As a plant growth retardant synthesized by chemical methods, paclobutrazol is often used to peach, sweet cherry, plum, apricot, apple and litchi to restrain excessively vegetative growth and to promote flowering. Although paclobutrazol hasn’t been registered in peach tree in China up to now, it has been extensively applied in peach production, more and more attention is been focused on its residue in peach fruits. Residual control determination, safe application techonology study and technical regulations have not been yet reported in peach production.In order to learn the residue, safety index, application effect and degradation dynamics of paclobutrazol after its application in peach or in soil, the residue degradation dynamics and terminal residue were studied in peach fruit and soil in field and green-house peach trees, taking3peach varieties as test material in2010and2011. We inferred the degradation half-life of paclobutrazol in peach fruit and blank soil, safety interval was made sure in peach application, discussed its safe application techonology, in addition, Maxmum Residue Limits in peach was recommended. All of these results that we achieved will give the technical support and theory basis for formulating MRLs of paclobutrazol in peach fruit, safe application techonology regulation and safety assessment system of paclobutrazol application in peach. The main results were as follows:1. Based on the residual dynamic results, we concluded that degradation half-life of paclobutrazol in peach fruit was8.5days, meaning relatively short degradation half-life (T1/2<30d) and rapid degradation.2. The residual dynamic results revealed that degradation half-life of paclobutrazol in blank soil was44.5days, meaning relatively long degradation half-life (T1/2>30d) and slow degradation.3. On the basis of the residual research of paclobutrazol in three peach varieties, according to MRLs<0.5mg/kg formulated by EU in peach fruit and carried out by China in apple and litchi fruit, it was safe to peach fruits and human being that under1500mg/L by foliar spraying two times at most(spraying interval time was36days) before no less than30days to harvest, so we deduced the safety interval of paclobutrazol was30days. While, the safety interval was35days in green-house peach(spraying interval time was15days). The method which soil application before peach germination, according to the canopy projection area to apply active ingredient paclobutrazol as0.0375-0.225g/m2, was safe to peach fruits, human being, because the residue in peach fruit was less than0.1mg/kg.4. Taking MRLs<0.5mg/kg as standard, the method of soil application active ingredient paclobutrazol as0.10-0.225g/m2canopy projection area before peach germination and using500mg/L3times,750mg/L or1000mg/L2times by foliar spraying during vigorous period of vegetative growth can not only control excessive growth, but also were safe to peach fruits and human being. If the strict regulation of MRLs<0.05mg/kg was adopted, we can only use soil application with dose of0.225g/m2in field or in green-house peach. If we take the extremely strict standard of MRLs<*0.01 mg/kg, paclobutrazol can not be used in peach production.5. According to the residual results and actual application in peach production, MRLs<0.5mg/kg of paclobutrazol in peach was recommended.