Cordyceps cateniannulata: a promising biological control agent for coffee leaf miner (Leucoptera coffeella)

The entomopathogenic fungus Cordyceps cateniannulata is a promising biocontrol agent against arthropod pests and has recently shown to be pathogenic to the coffee leaf miner under laboratory conditions. Considering the significant losses caused by this pest in coffee production and the limited use of fungal pathogens as tools to tackle this pest, we investigated the effects of Cordyceps cateniannulata on the coffee leaf miner in an in planta experiment and comparing the ability of C. cateniannulata, Beauveria bassiana and their mixture in the same assay. Prior to this, their in vitro interaction was evaluated. The growth of C. cateniannulata was unaffected by B. bassiana, whereas growth of B. bassiana was inhibited by 21.93% by C. cateniannulata. In the in planta experiment, fungal applications were initiated during larval stage and continued during pupation. All three treatments caused a high, and similar, mortality of coffee leaf miner pupae, with no additive or synergistic effect with the mixture. In the mixture, though, C. cateniannulata dominated sporulation from dead pupae, with a mean sporulation rate of 67%, compared to B. bassiana with 17%. Given that no fungus-induced mortality was observed in larvae within mines, exposure during pupation may represent a more susceptible stage for fungal infection under the conditions tested. While neither fungus gave rapid control of larvae, we propose that the effect on pupae, and thereby adults, could be of practical interest in suppressing populations of this coffee pest.