A novel predatory mite, Pronematus ubiquitous, in blackberry cultivation: effectiveness in biological control against the broad mite (Polyphagotarsonemus latus) and sensitivity to intraguild predation

Abstract: The broad mite, Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae), is a
pest of many commercial crops and has been found on plant species belonging to over 60
different plant families. Relatively recently (2014) it has been reported as a serious threat to
cultivated blackberries, Rubus fruticosus, in the United States, and since 2020 we have also
observed problems with this pest in Belgian commercial blackberry production. In this study
we evaluated the potential of a novel predatory mite, Pronematus ubiquitous (McGregor) (Acari: Iolinidae), for integrated control of P. latus. In a first phase, the lifecycle and migration characteristics of P. latus on blackberry plants were studied. Subsequently, the efficacy of P. ubiquitous was analyzed in the laboratory including survival, efficiency, food preferences, and intraguild predation (IGP) dynamics. Broad mites reproduced rapidly on blackberries, highlighting the urgency of developing effective control methods. Although P. ubiquitous showed some potential effectiveness as a preventative, uncertainties remain due to its preference for Tetranychus urticae spider mites and pollen over broad mites. In addition, unidirectional IGP with the predatory mites Neoseiulus californicus and Amblyseius andersoni was observed. Despite these findings, the definitive potential of P. ubiquitous as a control agent against P. latus remains inconclusive, necessitating further research, especially in commercial conditions. Nevertheless, this study has investigated the use of P. ubiquitous as part of an integrated control strategy to manage broad mite infestations in blackberry.