Abstract Powdery mildew (Erysiphe pulchra) is a devastating disease in nursery production of flowering dogwood (Cornus florida L.). Disease management relies heavily on season-long use of chemical fungicides and there is a demand for alternative strategies. An endophytic bacterium IMC8 was isolated from disease-free C. florida stem tissue, and was shown to be an effective biological control agent against E. pulchra in growth chamber, greenhouse and shadehouse environments. This isolate, identified as Bacillus thuringiensis, exhibited normal growth in NaCl concentrations up to 6%, pH 5 to 11, and temperatures up to 50°C. It was compatible with the conventional fungicide thiophanate methyl and clarified hydrophobic extract of neem seed oil at label recommended concentrations. The isolate IMC8 produced volatile compounds identified by GC/MS, which included antifungal and antibacterial compounds and suggested antibiosis as a mode of action. Scanning electron microscopy revealed lysis of powdery mildew spores and hyphae, which suggested parasitism as a second mode of action. These observations suggested that the isolate IMC8 has potential as a biological control agent in the management of powdery mildew on C. florida, and would tolerate a wide range of salinity, pH and high temperature conditions. It could be included as a component of integrated pest management in rotation or tank mix with lower levels of conventional fungicides, or used with clarified hydrophobic extract of neem seed oil.

中文翻译：

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内生苏云金芽孢杆菌对佛罗里达山茱萸白粉病的生物防治

摘要 白粉病 (Erysiphe pulchra) 是开花山茱萸 (Cornus florida L.) 苗圃生产中的一种毁灭性病害。疾病管理在很大程度上依赖于化学杀菌剂的季节性使用，因此需要替代策略。一种内生细菌 IMC8 从无病 C. florida 茎组织中分离出来，并被证明是一种有效的生物防治剂，可在生长室、温室和遮荫环境中对抗 E. pulchra。该分离物被鉴定为苏云金芽孢杆菌，在 NaCl 浓度高达 6%、pH 值 5 至 11 和温度高达 50°C 的情况下表现出正常生长。它与标签推荐浓度的常规杀真菌剂甲基硫菌灵和澄清的楝树籽油疏水提取物相容。分离物 IMC8 产生的挥发性化合物经 GC/MS 鉴定，其中包括抗真菌和抗菌化合物，并建议将抗菌作为一种作用方式。扫描电子显微镜显示白粉病孢子和菌丝裂解，这表明寄生是第二种作用方式。这些观察结果表明，分离物 IMC8 具有作为控制佛罗里达州白粉病的生物控制剂的潜力，并且可以耐受各种盐度、pH 值和高温条件。它可以作为综合害虫管理的一个组成部分，与较低水平的常规杀真菌剂混合使用，或与印楝籽油的澄清疏水提取物一起使用。这表明寄生是第二种作用方式。这些观察结果表明，分离物 IMC8 具有作为控制佛罗里达州白粉病的生物控制剂的潜力，并且可以耐受各种盐度、pH 值和高温条件。它可以作为综合害虫管理的一个组成部分，与较低水平的常规杀真菌剂混合使用，或与印楝籽油的澄清疏水提取物一起使用。这表明寄生是第二种作用方式。这些观察结果表明，分离物 IMC8 具有作为控制佛罗里达州白粉病的生物控制剂的潜力，并且可以耐受各种盐度、pH 值和高温条件。它可以作为综合害虫管理的一个组成部分，与较低水平的常规杀真菌剂混合使用，或与印楝籽油的澄清疏水提取物一起使用。