ABSTRACT

The commercial fungal biopesticide product PFR-97 20% WDG, based on the entomopathogenic fungus Cordyceps fumosorosea (Cfr), is registered in the U.S.A. for foliar sprays on citrus. The persistence of Cfr suspensions (10⁷ blastospores/mL) applied to grapefruit plants was evaluated under summer field conditions in southern Florida. Concurrently leaf disk bioassays were conducted to evaluate the pathogenicity of fungal residues on field-aged leaves against the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama. The results demonstrated that Cfr persisted for at least 35 days under our field conditions and caused up to 40% ACP mortality when used in bioassays. There was a general trend of higher colony forming unit counts and a correspondingly higher ACP mortality with the residue age of field-treated leaves. We hypothesise that under certain environmental conditions the Cfr propagule residues will germinate, produce hyphae, phialides and develop conidia on the leaf phylloplane over time. During this study, an adult citrus leafminer Phyllocnistis citrella (Stainton), another important pest of citrus was observed mycosed with Cfr hyphae and subsequently attached to the citrus leaf. Our study shows that Cfr can potentially provide supplemental longer-term management for ACP. Abiotic and biotic factors that may affect the field activity of Cfr and other mycoinsecticides over time are discussed.

摘要

商业真菌生物农药产品 PFR-97 20% WDG，基于昆虫病原真菌Cordyceps fumosorosea ( Cfr )，已在美国注册用于柑橘叶面喷雾。在佛罗里达州南部的夏季田间条件下，评估了施用于葡萄柚植物的Cfr悬浮液（10 ⁷芽生孢子/mL）的持久性。同时进行叶盘生物测定以评估田间老化叶片上的真菌残留物对亚洲柑橘木虱 (ACP)、Diaphorina citri Kuwayama 的致病性。结果表明，Cfr在我们的现场条件下持续至少 35 天，当用于生物测定时，导致高达 40% 的 ACP 死亡率。随着田间处理叶片的残留年龄，菌落形成单位数较高，ACP死亡率相应较高。我们假设在某些环境条件下，Cfr繁殖体残留物会随着时间的推移发芽、产生菌丝、菌丝并在叶平面上形成分生孢子。在这项研究中，观察到成年柑橘潜叶虫Phyllocnistis citrella (Stainton) 是另一种重要的柑橘害虫，它被Cfr菌丝感染，随后附着在柑橘叶上。我们的研究表明，Cfr可以潜在地为 ACP 提供补充的长期管理。讨论了随着时间的推移可能影响Cfr和其他mycoinsecticides的田间活动的非生物和生物因素。