Augmentative releases of the soil predatory mite Gaeolaelaps aculeifer reduce fruit damage caused by an invasive thrips in Mediterranean citrus

BACKGROUND: Soil-dwelling predatory mites of the family Laelapidae are augmentatively released for the biological control of several pests with an edaphic phase in numerous greenhouse crops. Yet, there is no information about the potential of releasing these predators to control pests in open field crops. We tested, during two consecutive years, the potential of augmentative releases of Gaeolaelaps aculeifer, alone or in combination with coco fiber discs as mulch, to reduce the damage caused on citrus fruits by the invasive thrips Pezothrips kellyanus in Mediterranean citrus. In a separate trial, we also compared different mulch types (coco fiber discs, rice husks or a mixture of sawdust and wheat bran) for their potential to support the establishment and population development of the predatory mites after their release. RESULTS: The percentage of unmarketable fruits caused by P. kellyanus was significantly reduced in the plots where G. aculeifer was released. The addition of coco fiber discs did not reduce further the percentage of unmarketable fruits. Sawdust + bran mulch was the most effective in preserving immature and adult predatory mite population after their release. CONCLUSION: Augmentative releases of G. aculeifer have the potential to reduce fruit damage caused by P. kellyanus in citrus. (c) 2020 Society of Chemical Industry.