Conidiobolus lunulus is a recently described entomophthoralean species isolated from leaf-cutter ants. This fungus discharges not only primary but also secondary conidia and microconidia of different shapes. Because nothing was known about the biology of the fungus, and its interactions with hosts, we first evaluated if its pathogenicity against leaf-cutter ants changes with the fungal age (time grown in vitro), and if it is related to the conidial structures produced. Afterwards, we tested its virulence at three combinations of temperature and relative humidity. In addition, we noted all visible causes of death by recovering different microorganisms from the dead, non-sterilized, ants to evaluate C. lunulus virulence when pathogens carried naturally by the ants were present. Finally, we used the conditions that lead to the highest mortality to evaluate fungal virulence to other host species, including non-leaf-cutter ants. Results indicated that C. lunulus was pathogenic from a culture age of 1 to 5 days, with a peak at 2-days-old, from which we registered median lethal times of 1–2 days and 85% of the cadavers with fungal conidiation. Our results suggest that primary conidia and moon-shaped microconidia were infective. Evaluations of mortality using 2-days-old cultures on several leaf-cutter ant colonies showed 1) significantly faster mortality of C. lunulus inoculated ants in comparison to controls, 2) significantly greater and faster mortality at 23.7 °C than at 21.2 °C, 3) significantly higher and faster mortality at 88% than at 57% RH, and 4) a significant reduction of other pathogens in C. lunulus inoculated ants in comparison to controls. C. lunulus was highly specific to leaf-cutter ants, as hardly any increase in mortality was observed on inoculated ants, and no conidia were recorded on cadavers of the other three non-leaf-cutter ant species tested. Our results highlight that C. lunulus is a very promising biological control agent against leaf-cutter ants.

C onidiobolus lunulus是最近描述的一种从切叶蚁中分离出来的虫害。这种真菌不仅排出初级而且排出不同形状的次级分生孢子和小分生孢子。由于对该真菌的生物学及其与宿主的相互作用一无所知，我们首先评估了它对切叶蚁的致病性是否随真菌年龄（体外生长时间）而变化，以及它是否与产生的分生孢子结构有关. 之后，我们在三种温度和相对湿度组合下测试了其毒力。此外，我们通过从死去的、未经消毒的蚂蚁身上回收不同的微生物来评估C. lunulus当蚂蚁自然携带的病原体存在时的毒力。最后，我们使用导致最高死亡率的条件来评估真菌对其他宿主物种（包括非切叶蚁）的毒力。结果表明，C. lunulus从 1 至 5 天的培养龄开始具有致病性，在 2 天龄时达到高峰，我们记录了 1-2 天的中位致死时间和 85% 的尸体带有真菌分生孢子。我们的结果表明初级分生孢子和月形小分生孢子具有传染性。使用 2 天大的培养物对几个切叶蚁群的死亡率进行评估表明 1) C. lunulus 的死亡率显着加快与对照组相比，接种的蚂蚁，2) 23.7 °C 下的死亡率明显高于 21.2 °C 下的死亡率，3) 88% 下的死亡率明显高于 57% RH 下的死亡率，以及 4) 其他病原体的显着减少与对照相比，C. lunulus接种了蚂蚁。C. lunulus对切​​叶蚁具有高度特异性，因为在接种的蚂蚁身上几乎没有观察到死亡率的增加，并且在其他三种非切叶蚁物种的尸体上没有记录到分生孢子。我们的结果强调，C. lunulus是一种非常有前途的针对切叶蚁的生物防治剂。