Understanding the plant-host-environment interactions of Halyomorpha halys (Hemiptera: Pentatomidae) for effective pest management strategies

An agroecosystem is a complex and dynamic context where physical, chemical, and biological processes play a role in the interactions among all organisms that respond to the environment. Integrated pest management (IPM) principles are based on the application of different tools for pest control to minimize economic, environmental and social costs. Pest-management programs must ensure that pests in the agroecosystem can be managed over the long term without adverse consequences. A deep knowledge of the abovementioned interactions is crucial to define effective management strategies against invasive species like Halyomorpha halys (Hemiptera: Pentatomidae). To contrast repeated colonization patterns throughout the season, broad-spectrum insecticides are widely used to manage H. halys infestations, which negatively impact agricultural production's sustainability in terms of economic, environmental, and human health aspects. Effective alternatives to manage this pest are needed to reduce dependence on synthetic pesticides. Knowledge of the main drivers of pest population dynamics is the key to developing successful IPM strategies. In the present thesis, the effect of climatic conditions on H. halys phenology was studied, characterizing areas with different suitability for the pest population in development. The effect of host-plant physiological conditions, drought stress status affected H. halys behaviour. The identification of volatile organic compounds released by drought-stressed and no-stressed plants can help in developing new tools for pest management. Three chapters of the thesis present studies on novel management tools already available for growers. In Chapter 4 the use of different sulphur-based fungicides was evaluated in laboratory, semi-field and field conditions. Results showed that the application of sulphur-based products negatively affects H. halys infestation lowering infestation density and fruit damages in pome fruit. Chapter 5 focused on a novel pheromone-based mass trapping system that proved to be an effective tool in H. halys management. The study highlighted optimal conditions for the use of these tools and focusing in particular on trap density in field, distance from the orchard and time of application providing information to increase the efficacy. In Chapter 6, the use of mass trapping systems was also combined with sulphur-based products in a push-pull strategy.