Data Beretta et al. 2024 Biological Control 188 105437. https://doi.org/10.1016/j.biocontrol.2023.105437

Biological pest control is successful in many agricultural systems, yet various pests can still not be controlled withnatural enemies. Examples are invasive thrips species such as Echinothrips americanus Morgan and Thrips parvispinus(Karny) in Europe. The lack of biological control of these pests in several crops has been subscribed totheir complex life cycle and cryptic behaviours, but their antipredator behaviours may prevent successful controland have not been studied extensively. One of these behaviours is the potential of thrips to kill the eggs ofpredatory mites, which we quantified. Furthermore, we observed the behaviour of first- and second-instar thripslarvae when attacked by starved predatory mites Amblyseius swirskii Athias-Henriot. For comparison, we includedFrankliniella occidentalis (Pergande), which shows an array of defensive behaviours, but can be controlled successfullyby several species of predatory mites. Second-instar larvae and adults of F. occidentalis and T. parvispinuskilled predator eggs, but E. americanus did not. First- and second-instar larvae of all three species swung theirabdomen to defend themselves, and F. occidentalis and T. parvispinus produced anal droplets, which are alsoinvolved in defence. Predators were not successful in attacking any second-instar larvae during 15-minute observations,which is sufficiently long for an attack. First-instar larvae of F. occidentalis and T. parvispinus weresometimes successfully attacked by the predatory mite before they could mount a defence, but first-instarE. americanus always defended themselves and were almost never preyed upon. Cooling thrips larvae to suppressantipredator behaviour increased predation for all species and stages, except for first instars ofF. occidentalis. In conclusion, the lack of successful control of E. americanus is not caused by killing predator eggs,but by the efficient defensive behaviour of both larval instars. Our study furthermore suggests that T. parvispinuscan potentially be controlled by A. swirskii.