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Dryocosmus kuriphilus Yasumatsu (Hymenoptera Cynipidae) was first recorded in Sardinia (Italy) in 2007. Two years later a biological control program started with the introduction of its non-native parasitoid, Torymus sinensis Kamijo (Hymenoptera Torymidae). Over a nine-year period (2009–2017), data on the relative abundance of D. kuriphilus, its native parasitoids and T. sinensis were collected. Native parasitoids reacted quickly to the large availability of hosts. However, a dramatic change in the abundance of each native species was recorded from year to year. In the first few years, the native parasitoid community and pest abundance did not fluctuate much. The turning point was 2014, when, at the same time, the native parasitoid populations increased and the T. sinensis populations also began to increase. In the following year, both the D. kuriphilus and native parasitoid populations decreased considerably, whereas the T. sinensis populations reached over 50% parasitism. The univoltine D. kuriphilus acted as an asynchronous resource for native bivoltine parasitoids. An asynchronous host-parasitoid interaction produces wide fluctuations in their populations. In this case, D. kuriphilus strongly altered the local community, which was subjected to a chaotic change in composition and species abundance. When T. sinensis became established, it monopolized the pest, making this resource unavailable to native parasitoids that returned to attack almost exclusively the native oak cynipids. In fact, the successful control of D. kuriphilus by the introduction of T. sinensis rebalanced the situation that had been altered by the arrival of the invasive pest.

Cardoon (Cynara cardunculus var. altilis) has gained interest as a novel crop for bioenergy, multipurpose uses, and industrial bio‐based productions, also based on the achene yield. However, achenes can be affected by various insects, which are considered as minor pests in traditional Cynara crops. Nonetheless, very little information is available on these pests. The aim of this research was to identify the frequency of different insect species with particular regard to weevils, and to quantify the achene yields and losses caused by these spermophagous insects on cardoon. Field measurements were performed across three consecutive years in Sardinia (Italy). Mature cardoon heads of different insertion orders (primary, secondary, tertiary and quaternary heads, respectively) were manually harvested. For each head, the achenes were counted and weighed, and bare receptacles were scored in terms of damaged areas by weevil larvae (i.e., the percentage of total area). The results highlighted a higher frequency of Larinus scolymi (90%) compared to Larinus cynarae. The total number of achenes per head and the 1000‐achene weight were markedly affected by head order. Actual achene yield ranged from 86.8 to 107.9 g per plant. The estimates of achene yield losses per plant due to Larinus weevils ranged from 36.3 in 2014 to 113.0 g per plant in 2015, corresponding to about 0.4 to 1.1 t per hectare, respectively. Our results showed that achene losses were caused mainly by L. scolymi, indicating that cardoon crop profitability could be jeopardised in the absence of insect controls. Based on the experimental data, appropriate strategies aimed at controlling weevil infestations are needed to preserve cardoon achene yields.