Occurrence Dynamics of Citrus Target Spot in Wanzhou District of Chongqing City and Compound Fungicide Screening of Pseudofabraea Citricarpa

Abstract

To explore the occurrence dynamics and infection characteristics of citrus target spot, and screen effective fungicides and provide data support for citrus safe production. Two orchards with different altitudes and different management levels in Shuangshi community and Baiyan Village of Wanzhou District Chongqing city were selected to follow up the occurrence of citrus target spot. At the same time, the inhibition effects of 6 compound fungicides to Pseud of abraea Citricarpa (Citrus Target spot) were determined by the mycelial growth rate inhibition method. The results showed that, in December of 2021 to March of 2022, in the 2 orchards, the average disease spot, number of falling leaf showed a trend of reduce after the first rise, and incidence and disease index were characterized by rising gradually along with the passage of time. From late to the end of January, there were more rainy and foggy days, and the temperature dropped sharply, which aggravated the defoliation. Orchard 1 was with higher altitude 750 m and loose management, and the disease outbreak came more rapidly and severely. While in orchard 2, the lower altitude, higher management level and stronger tree made the disease be later and lighter than orchard 1. Further studies of compound fungicide screening showed that the EC50 against Ps. Citricarpa, from low to high, was 40% Tebuconazole·Prochloraz (0.03295)<13% Thifluzamide·Hexaconazole (0.03634)<30% Difenoconazole·Propiconazole (0.03881)<40% Difenoconazole·Pyraclostrobin (0.30849)<30% Thifluzamide·Tebuconazole (0.90167)<33 % Kasugamycin·Copper Quinoline (2.92935). These fungicides can be used for further research in the field test.