Tarnowski T L B, Savelle A T, Scherm H
Department of Plant Pathology, University of Georgia, Athens 30602.
Plant Dis. 2008 Jun;92(6):961-965. doi: 10.1094/PDIS-92-6-0961.
The activity of fenbuconazole and azoxystrobin applied to blueberry flowers at different phenological stages against subsequent gynoecial infection by the mummy berry fungus Monilinia vaccinii-corymbosi was evaluated. In the greenhouse, potted blueberry plants having flower clusters at five distinct stages (from bud scale separation to anthesis) were treated with the two fungicides. One day after anthesis (between 1 and 15 days after fungicide treatment), individual flowers were detached and inoculated with conidia of M. vaccinii-corymbosi in the laboratory. Four days after inoculation, hyphal ingress into the style was determined microscopically as a measure of fungicide efficacy. Results revealed a significant flower stage effect (P < 0.0001), whereby only fungicide application at anthesis but not at the four preanthesis stages reduced subsequent fungal ingress into the style. There was no significant difference between the two fungicides (P > 0.50) nor was there a significant fungicide-flower stage interaction (P > 0.30). In the field during 2 years, mature blueberry plants were treated with the two fungicides and exposed to natural pathogen inoculum. At the time of application, flower clusters at anthesis and at three preanthesis stages were selected and tagged. Mummy berry incidence in fruit developing from the tagged clusters was assessed to determine treatment effects. Whereas fenbuconazole lowered disease incidence for all preanthesis stages, azoxystrobin was effective only at the latest preanthesis stage. The discrepancy between these results and those of the greenhouse study (where there was no preanthesis activity of either fungicide) indirectly suggests post-infection fungicidal activity in the ovary, the base of which was exposed to the fungicide spray at the time of treatment for all flower phenology stages. Thus, although there appears to be insufficient translocation of the two fungicides in flowers treated at preanthesis stages to prevent stylar ingress by the pathogen, fungicidal activity in the ovary may be sufficient to halt subsequent fungal colonization, especially for fenbuconazole. To prescribe the most effective management program for flower-infecting fungi, translocation and post-infection activity of fungicides in floral tissues must be better understood.
评估了在不同物候期将苯氟康唑和嘧菌酯施用于蓝莓花上，对随后由僵果病菌（Monilinia vaccinii-corymbosi）引起的雌蕊感染的防治效果。在温室中，对处于五个不同阶段（从芽鳞片分离到开花）的带有花簇的盆栽蓝莓植株用这两种杀菌剂进行处理。开花后一天（在杀菌剂处理后1至15天之间），将单个花朵摘下并在实验室中接种僵果病菌的分生孢子。接种后四天，通过显微镜观察菌丝侵入花柱的情况来衡量杀菌剂的效果。结果显示出显著的花期效应（P < 0.0001），即只有在开花期施用杀菌剂，而在开花前的四个阶段施用则不能减少随后病菌菌丝对花柱的侵入。两种杀菌剂之间没有显著差异（P > 0.50），杀菌剂与花期之间也没有显著的交互作用（P > 0.30）。在两年的田间试验中，对成熟的蓝莓植株用这两种杀菌剂进行处理，并使其暴露于自然病原菌接种环境中。在施药时，选择并标记处于开花期和三个开花前期阶段的花簇。评估从标记花簇发育而来的果实中的僵果发病率，以确定处理效果。虽然苯氟康唑降低了所有开花前期阶段的病害发病率，但嘧菌酯仅在最晚的开花前期阶段有效。这些结果与温室研究结果（两种杀菌剂在开花前均无活性）之间的差异间接表明，在子房中有感染后杀菌活性，在处理所有花期阶段时，子房基部都接触到了杀菌剂喷雾。因此，尽管在开花前期阶段处理的花朵中，这两种杀菌剂似乎没有足够的内吸作用来防止病原菌侵入花柱，但子房中的杀菌活性可能足以阻止随后的真菌定殖，尤其是对于苯氟康唑而言。为了制定针对感染花朵真菌的最有效管理方案，必须更好地了解杀菌剂在花组织中的内吸作用和感染后活性。
