The bacterium Xylella fastidiosa subspecies multiplex causes phony peach disease (PPD), a serious disease of peach in the southeastern United States. The current management strategy for PPD is removal of symptomatic trees, but other management options should be explored. Field efficacy trials with plant growth stimulants and plant defense activators were conducted in orchards of ‘Julyprince’ in 2021 and 2022, and ‘Springprince’ in 2021. Treatments were applied either as a foliar or root drench application once a month for three consecutive months during the growing season. Treatments included Rio, ProGibb 40SG, Maximizer, Actigard 50WG, and K-phite 7LP. In 2021, ProGibb 40SG provided increased shoot growth in both varieties, but cycle threshold (Ct) values did not suggest that any treatment affected bacterial titer. In 2022, applications were initiated one month later and no significant effects on shoot growth parameters or bacterial titer were observed among treatments. The reduction in symptoms after ProGibb 40SG application and the fact that healthy trees responded similarly indicates the growth response was due to the plant responding to the hormonal treatment, and not an effect on the pathogen, the titer of which remained similar. Thus, ProGibb 40SG may have very limited value for improving PPD tree health.

细菌Xylella fastidiosa亚种多重导致假桃病 (PPD)，这是美国东南部桃子的一种严重病害。目前 PPD 的管理策略是移除有症状的树木，但应探索其他管理方案。2021 年和 2022 年在“Julyprince”的果园和 2021 年在“Springprince”的果园进行了植物生长刺激剂和植物防御激活剂的田间药效试验。在连续三个月内，每月一次进行叶面或根部浸润处理。生长季节。处理包括 Rio、ProGibb 40SG、Maximizer、Actigard 50WG 和 K-phite 7LP。2021 年，ProGibb 40SG 增加了两个品种的枝条生长，但循环阈值 (Ct) 值并未表明任何处理都会影响细菌滴度。2022年，一个月后开始施用，并且在处理之间没有观察到对枝条生长参数或细菌滴度的显着影响。施用 ProGibb 40SG 后症状减轻以及健康树木反应相似这一事实表明生长反应是由于植物对激素处理有反应，而不是对病原体的影响，病原体的效价保持相似。因此，ProGibb 40SG 对改善 PPD 树健康的价值可能非常有限。