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Autochthonous biological resources: the potential of the mirid Dicyphus cerastii for biological control in protected crops

Publication . Duarte, Gonçalo Nuno Abraços Henriques Gomes; Figueiredo, Elisabete; Silva, Elsa Maria Borges da

Dicyphine mirids (Hemiptera: Miridae: Bryocorinae: Dicyphini) are important biological control agents (BCAs) in protected crops. Despite this, only two species are commercially available in Europe, Macrolophus pygmaeus and Nesidiocoris tenuis. The former establishes slowly, and the latter can cause damage to tomato crops. Dicyphus cerastii occurs along the Mediterranean basin and spontaneously colonizes protected tomato crops in Portugal, where it often co-occurs with N. tenuis. Dicyphus cerastii has been previously observed feeding on several tomato pests. However, many aspects of its biology and ecology remain poorly studied. This thesis intended to better understand the role of D. cerastii as BCA, and whether it can be an alternative or a complement to N. tenuis, by gathering information on its biological traits, predatory interactions, and phytophagous behaviour. Our results indicate that D. cerastii may be a valuable predator in tomato crops since it showed high voracity on important pests even when compared to other dicyphines. Moreover, we observed that, despite being able to damage fruit and cause flower abortion, the impact of D. cerastii on the tomato plant is less severe than N. tenuis. Though mirids only engaged in intraguild predation in absence of extraguild prey, D. cerastii preyed more often on N. tenuis than otherwise. We also found that D. cerastii had a longer developmental period, higher mortality, and lower reproductive rate than N. tenuis, particularly above 20 °C, which could be the main reason behind the apparent seasonal competitive displacement by N. tenuis. Overall, this thesis contributed to increase the knowledge on the dicyphine complex of protected crops by understanding the services and disservices provided by D. cerastii. Given its better performance at lower temperatures and high voracity, D. cerastii may complement N. tenuis in spring conditions in Portugal, which further evidences the importance of conservation of autochthonous biological resources.

2024-06-20Doctoral thesis

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