New potential strains for controlling Spodoptera frugiperda in China: Cordyceps cateniannulata and Metarhizium rileyi

Abstract

Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), an invasive pest, was identified in China in early 2019. This pest is a serious threat to food, especially maize production. Consequently, it is necessary to use biological control to reduce the damage caused by S. frugiperda. Furthermore, it is important to find new entomopathogenic fungi or a local wild parasitic isolate to control this pest. Here, one fungus was found infecting S. frugiperda larvae in China. Isolated colonies were identified as Metarhizium rileyi (Farlow) Kepler, S.A. Rehner & Humber (Hypocreales: Clavicipitaceae) using morphological and molecular methods. Bioassay studies with purified conidial suspensions further confirmed the infectivity to 4th instar S. frugiperda larvae. The results showed that no S. frugiperda larvae survived after being treated with a spore suspension of M. rileyi GZUIFR-LS01 or Cordyceps cateniannulata (Z.Q. Liang) Kepler, B. Shrestha & Spatafora (Hypocreales: Cordycipitaceae) GZUIFR-S22 for seven days at 90% RH. However, at 75% RH, 13% and 48% of larvae survived after seven days of exposure to M. rileyi GZUIFR-LS01 and C. cateniannulata GZUIFR-S22, respectively. Additionally, C. cateniannulata strain GZUIFR-S22 led to a survival rate of less than 50% in S. frugiperda larvae after two days of treatment at 90% RH. This is the first report of the pathogenicity of C. cateniannulata against S. frugiperda.