“Alien versus predator”: predatory effect of coccinellid Exochomus quadripustulatus on the scale insect Toumeyella parvicornis . An open‐field experimentation on the Pinus pinea of Rome

The tortoise scale insect ( Toumeyella parvicornis ) is rapidly spreading in stone pine ( Pinus pinea ) forests and urban parks of Mediterranean Europe. Its current distribution and potential spread is concerning as, so far, it already includes three different European countries. Pest management strategies based on endotherapic treatments have a limited time coverage and are unfeasible on large scales. Biological control can be a valuable alternative to contain the spread of T. parvicornis , as highlighted by some recent studies conducted with predators under controlled conditions. Although promising outcomes, open‐field efficacy is still poorly explored. This study aimed to fill this gap in knowledge through an open‐field assessment of the predation impact of Exochomus quadripustulatus and its capability of reducing T. parvicornis infestation level. Adult ladybug females were released on stone pine groups divided as follows: (i) plants treated only with ladybugs, (ii) plants pre‐treated with bio‐insecticide prior the release of the ladybugs, and (iii) an untreated control. The stone pine groups that received the ladybugs application, showed a lower infestation level (in terms of T. parvicornis adult females) than the untreated control, for most of the evaluation period. Results showed, for the first time, evidence of E. quadripustulatus efficacy in open‐field applications, confirming the previously positive outcomes observed under laboratory and semi‐field conditions. The outcomes of this study, accordingly, open the door to future biological control programs.