Journal of Zhejiang Agricultural Sciences ›› 2026, Vol. 67 ›› Issue (2): 455-462.DOI: 10.16178/j.issn.0528-9017.20250483

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Screening of fungicides for control of citrus brown spot caused by Alternaria spp.

LIAN Jianjun1(), XU Hubin2, CHENG Ying2, ZHANG Junmei1, CHEN Xugen3, WU Qiqi1, DENG Liangdong1, JIAO Chen2, LI Hongye2()   

  1. 1.Qingyuan County Bureau of Agriculture and Rural Affairs,Lishui 323800,Zhejiang
    2.Institute of Biotechnology,Zhejiang University,Hangzhou 310058,Zhejiang
    3.Qingyuan Fengzhimi Family Farm,Lishui 323800,Zhejiang
  • Received:2025-07-07 Online:2026-02-28 Published:2026-03-07
  • Contact: LI Hongye

Abstract:

Alternaria brown spot (ABS),commonly referred to as citrus brown spot,is an emerging and important fungal disease affecting some mandarins and their hybrids in China. The pathogens can infect all young tissues of susceptible citrus varieties,and their fruit can be infected throughout the entire growth period. This disease often causes massive defoliation,fruit drop,shoot blight,and even causes fruitless on susceptible cultivars if the weather conditions are extremely favorable for the outbreak of this disease. However,to date,no fungicide has been registered for the control of this disease in China. In this study,we evaluated the inhibitory activity on the mycelial growth of two varieties of brown spot disease fungi,field control effect and orchard cleanup treatments effect of different single agents,compound agents of fungicides and fungicide combinations. The results showed that at an active ingredient concentration of 1 μg·mL-1,the inhibition rates of fludioxonil (single agent),fluxapyroxad-cyflufenamid,pydiflumetofen-fludioxonil,pydiflumetofen-difenoconazole,and azoxystrobin-fludioxonil on mycelial growth all exceeded 90%. Field efficacy trials indicated that pydiflumetofen-difenoconazole exhibited better control effect against ABS,and the control effects of the mixed treatment of pydiflumetofen and fludioxonil,pydiflumetofen and mancozeb were all good,which can effectively reduce the rate of diseased shoots and the number of fallen leaves. In addition,orchard cleanup treatments with Bordeaux mixture and lime sulfur could effectively control ABS and significantly reduce the incidence of diseased shoots. The findings of this study provide data support and theoretical guidance for the selection of fungicides for the management of citrus brown spot.

Key words: citrus brown spot, fungicide, in vitro antifungal effect, orchard control effect

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