Most hypovirulence in the chestnut blight fungus, Cryphonectria parasitica, is associated with infection by fungal viruses in the family Hypoviridae. Hypovirulence has controlled chestnut blight well in some locations in Europe and in Michigan in the United States. In contrast, with few exceptions, biological control has failed almost completely in eastern North America. Therapeutic treatment of individual cankers is successful in most cases, but the success of hypovirulence at the population level depends on the natural spread of viruses. Characteristics of three interacting trophic levels (virus, fungus, and tree), plus the environment, determine the success or failure of hypovirulence. Vegetative incompatibility restricts virus transmission, but this factor alone is a poor predictor of biological control. Any factor reducing the rate of chestnut blight epidemics enhances hypovirus invasion. Overall, however, not enough is understood about the epidemiological dynamics of this system to determine the crucial factors regulating the establishment of hypovirulence in chestnut forests.

中文翻译：

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低毒力对栗疫病的生物控制：关键分析。

栗叶枯萎真菌中的大多数低毒力与甲状病毒科的真菌病毒感染有关。低毒力已经很好地控制了欧洲和美国密歇根州的栗子疫病。相反，除少数例外，生物控制在北美东部几乎完全失败。在大多数情况下，对单个溃疡病的治疗是成功的，但是在人群水平上低毒力的成功取决于病毒的自然传播。三种相互作用的营养水平（病毒，真菌和树）以及环境的特征决定了低毒力的成败。营养不相容性限制了病毒的传播，但是仅此因素就不能很好地预测生物控制。降低板栗疫病流行率的任何因素都会增加次病毒的入侵。但是，总体而言，对该系统的流行病学动态了解不足，无法确定调节栗树林中低毒力建立的关键因素。