Half Friend, Half Enemy? Comparative Phytophagy between Two Dicyphini Species (Hemiptera: Miridae)

SIMPLE SUMMARY: Omnivorous predators, such as some mirids, are important biological control agents in several vegetable crops since they are generalists and can survive in the crop in the absence of prey. Nesidiocoris tenuis is a mirid used worldwide and its phytophagy is well known, which is not the case for the Palearctic Dicyphus cerastii. To use the latter in biological control it is crucial to evaluate the damage it causes to plants. We compared these two mirid species, under laboratory and semi-field conditions, regarding the damage they caused to plants and fruit, and their location on the plant versus on the fruit. Both species produced plant damage (scar punctures on leaves and necrotic patches on petioles) and caused flower abortion, at a similar level, however, only N. tenuis produced necrotic rings. Overall, N. tenuis females produced more damage to tomato fruit than D. cerastii. There was an increased frequency of D. cerastii females found on the plants over time, which did not happen with N. tenuis. Our results suggested that although D. cerastii caused less damage to tomato fruit than N. tenuis, it did feed on the fruit and could cause floral abortion, which requires field evaluation and caution in its use. ABSTRACT: Despite their importance as biological control agents, zoophytophagous dicyphine mirids can produce economically important damage. We evaluated the phytophagy and potential impact on tomato plants of Dicyphus cerastii and Nesidiocoris tenuis. We developed a study in three parts: (i) a semi-field trial to characterize the type of plant damage produced by these species on caged tomato plants; (ii) a laboratory experiment to assess the effect of fruit ripeness, mirid age, and prey availability on feeding injuries on fruit; and (iii) a laboratory assay to compare the position of both species on either fruit or plants, over time. Both species produced plant damage, however, although both species produced scar punctures on leaves and necrotic patches on petioles, only N. tenuis produced necrotic rings. Both species caused flower abortion at a similar level. Overall, N. tenuis females produced more damage to tomato fruit than D. cerastii. There was an increased frequency of D. cerastii females found on the plants over time, which did not happen with N. tenuis. Our results suggested that, although D. cerastii caused less damage to fruit than N. tenuis, it still fed on them and could cause floral abortion, which requires field evaluation and caution in its use in biological control strategies.