Moyo Providence, Fialho Régis Oliveira, Silva Junior Geraldo José, Fourie Paul
Citrus Research International Nelspruit South Africa.
Department of Plant Pathology and Nematology University of São Paulo Piracicaba São Paulo Brazil.
Plant Environ Interact. 2025 Jan 26;6(1):e70031. doi: 10.1002/pei3.70031. eCollection 2025 Feb.
Citrus black spot (CBS), caused by , is an important fungal disease of citrus. Higher CBS severity has been associated with infections at the young and green stages of fruit. The length of the fruit susceptibility period may be influenced by the amount of inoculum and the climate of the citrus growing region. This study was conducted in orchards across two South African provinces to assess the intensity of CBS under two conditions: (i) unsprayed fruit of Valencia sweet orange, Nova, and Empress mandarins inoculated with at 10, 10, and 10 pycnidiospores/mL at various intervals after fruit set, from October (petal fall stage) to March (for mandarins) or June (for sweet orange), and (ii) non-inoculated Valencia fruit from orchards subjected to spray programs ranging from one to nine applications between October and June. Higher CBS intensity was observed in Valencia fruit inoculated between November and January, with an average disease severity index (DSI) of 0.94, compared to a significantly lower (0.07) for fruit inoculated from February to June. Inoculations in November or December for Nova mandarins and in December for Empress with 10 pycnidiospores/mL resulted in higher CBS intensity compared to those with lower pycnidiospore concentrations. The absence of fungicide applications from October to December during the 2017-2018 season led to increased CBS intensity, with a DSI of ~0.47, a value which was not significantly different from that of non-treated control (NTC) trees. Leaving sweet orange trees unprotected from January onwards did not significantly increase the CBS intensity. These results confirm that citrus growers should focus on protecting citrus fruit, against infection, in their dark green and young stages (c.15-30 mm diameter) to control CBS.
柑橘黑点病（CBS）由[病原体名称未给出]引起，是柑橘的一种重要真菌病害。CBS严重程度较高与果实幼嫩和绿色阶段的[病原体名称未给出]感染有关。果实感病期的长短可能受接种体数量和柑橘种植地区气候的影响。本研究在南非两个省份的果园进行，以评估在两种条件下CBS的发病强度：（i）伏令夏橙、诺瓦橘和帝王橘的未喷洒果实，在坐果后的不同时间间隔（从10月（花瓣脱落期）到3月（针对橘类）或6月（针对甜橙）），分别用浓度为10、10和10个分生孢子/毫升的[病原体名称未给出]进行接种；（ii）10月至6月期间，对果园中未接种的伏令夏橙果实进行1至9次喷雾处理。11月至1月接种的伏令夏橙果实中观察到较高的CBS发病强度，平均病害严重指数（DSI）为0.94，而2月至6月接种的果实该指数显著较低（0.07）。11月或12月对诺瓦橘以及12月对帝王橘用10个分生孢子/毫升进行接种，与较低分生孢子浓度接种相比，导致更高的CBS发病强度。2017 - 2018年季节10月至12月未施用杀菌剂导致CBS发病强度增加，DSI约为0.47，该值与未处理对照（NTC）树的值无显著差异。1月起不对甜橙树进行保护不会显著增加CBS发病强度。这些结果证实，柑橘种植者应着重在果实深绿色和幼嫩阶段（直径约15 - 30毫米）保护柑橘果实免受[病原体名称未给出]感染，以控制CBS。
