Abstract:

Flusilazole, myclobutanil and tebuconazole are registered for the control of pear scab, and all of them have good control effects. In order to screen pesticides with high control efficacy and low residues, the residues and dissipation characteristics of the above three fungicides in pears and soil were studied in this paper by gas chromatography and liquid chromatography-mass spectrometry methods. The results showed that the half-life of flusilazole, myclobutanil and tebuconazole in pears was 8.83 d, 14.44 d and 4.70 d, respectively, and the half-life of the above three fungicides in soil was 18.38 d, 17.32 d and 16.50 d, respectively, tebuconazole had the fastest dissipation rate in pears and soil. In China, the maximum residue limit (MRL) of flusilazole, myclobutanil and tebuconazole in pears is 0.2 mg/kg, 0.5mg/kg and 0.5 mg/kg, respectively. For the field trial, the recommended dosage and 1.5 times recommended dosage of the three fungicides were applied to pears and soil respectively. Twenty-one days after the last treatment, the maximum harvest residue of flusilazole in pears was 0.109 mg/kg, reaching 54.5% of the MRL value; the maximum harvest residue of myclobutanil in pears was 0.42 mg/kg, reaching 84% of the MRL value; and the maximum harvest residue of tebuconazole in pears was <0.1 mg/kg, which was far lower than the MRL value. With the comprehensive analysis of the residues and dissipation characteristics of the three fungicides in pears and soil, it is found that the risk of tebuconazole was lower in diet and environment. The results of this paper provide a theoretical basis for the selection of pesticides with high control efficiency and low residue in the control of pear scab.

Key words: flusilazole, myclobutanil, tebuconazole, pear, residue