Potential of entomopathogenic fungi and nematodes against the two cryptic species Parahypopta caestrum and Cossus cossus in laboratory assays

Pests residing in cryptic habitats, as insects which bore into the plant tissue (woodboring insects) or under the bark (bark beetles)the soil (wireworms) are very difficult to control because chemical pesticides are not able to reach the target. Usually, the only option to reduce infestations is the removal and destruction of infested or injured plants. One potential alternative to chemical insecticides for the control of cryptic insects can be the use of microbial control agents, as entomopathogenic nematodes (EPNs) and fungi (EPFs), because they may be able to penetrate into cryptic habitats and to be horizontally transmitted within the pest populations. Parahypopta caestrum (HUbner) and Cossus cossus (L.) (Lepidoptera, Cossidae) are highly-destructive cryptic pests in Europe. Parahypopta cuestrumcan I be considered the key pest of Asparagus spp. in Italy, due to its high destructiveness and the lack of effective control options available. The soil-borne larvae bore mines into the roots and the shoots, causing the total destruction of plantations after 2-3 I years. The goat moth C. cossus (L.) is a wood-boring pest whose larvae bore large galleries under the bark and even deeply into trunks and branches of fruit and forest trees, reducing plant growth and vigour, and causing limbs and branches to fall. Preliminary assays were performed in laboratory conditions in order to evaluate the infectivity of several EPF and EPN autochthonous strains against P. caestrum and C. cossus larvae. Results revealed the efficacy of these microbial control agents in killing the larvae, although a wide inter- and intra-specific variability in virulence was detected among different microbial strains. Considering the lack of effective chemical control means, the microbial control of the Asparagus moth and the goat moth by EPNs and EPFs reveals promising perspectives and needs further investigations.