Natural and experimental fungal colonisation of Lycorma delicatula egg masses suggests reduced hatch success

The spotted lanternfly, Lycorma delicatula (White), is an invasive planthopper that threatens various agricultural and wild plant species. Controlling L. delicatula is critical due to its rapid spread and agricultural impact, but management efforts are hindered by limited knowledge of its reproductive biology and microbial interactions. This study examines how fungal colonisation affects hatch efficacy in L. delicatula eggs and evaluates entomopathogenic fungi as a biocontrol strategy. Fresh L. delicatula egg masses were aseptically collected in April 2023, revealing initial fungal colonisation. Egg masses were stored in darkness at 9°C and 30–35% relative humidity. Monthly incubations from April to September at 22°C and 65–70% humidity showed increased mycelial colonisation over time, correlating with a reduction in hatch rate after 60 days (R2 = 0.66). Dilution plating of eggs stored for 150 days yielded 106 colony-forming units, indicating bioamplification of entomopathogenic fungi such as Cladosporium spp. and Fusarium spp. Molecular identification confirmed that Pseudomonas fluorescens, a known antifungal bacterium, inhibited growth of Cladosporium spp. (p < 0.05). Six entomopathogenic fungal isolates were tested against L. delicatula egg masses in vitro, with Samsoniella sp. showing increased mycelial colonisation (p < 0.001), while P. fluorescens exhibited the least (p = 0.008). These findings document the natural colonisation of L. delicatula egg masses by entomopathogenic fungi, suggesting that high-concentration spore applications could be a viable biocontrol strategy to target the stationary egg mass life stage and curb population growth.