Symbiont-Targeted Control of Halyomorpha halys Does Not Affect Local Insect Diversity in a Hazelnut Orchard

Harmless crop-associated insect communities are a fundamental part of the agroecosystem. Their potential as a reservoir of natural enemies of pests has encouraged their conservation through the development of low-impact pest management programs. The brown marmorated stink bug, Halyomorpha halys, represents a serious threat to Italian hazelnut production. Laboratory and field experiments confirmed the susceptibility of this pest to the disruption of the obligated symbiotic interaction with gut bacteria, paving the way for the development of the symbiont-targeted control strategy. Here we present the results of a three-year field assessment of symbiont-targeted control in a hazelnut orchard in northwestern Italy. The use of a biocomplex to disrupt symbiont acquisition by H. halys nymphs was compared to the use of lambda-cyhalothrin insecticide. The effects on the local entomofauna were assessed, as were the trend of H. halys population and the damage caused by stink bugs to harvested hazelnuts. The insecticide consistently reduced the insect diversity in the field, while the anti-symbiont biocomplex had no effect. However, the control of the H. halys population and the stink bug-induced damage to hazelnuts varied over the years in the field plot submitted to the symbiont-targeted approach. Our results indicate that the symbiont-targeted control does not interfere with local insect communities. Key aspects for improving the effectiveness of this tactic are discussed.