An iolinid predatory mite feeds on powdery mildew

Despite reports of arthropods successfully controlling plant diseases, this strategy is still underexplored in biological disease management. Iolinids are omnivorous predatory mites that occur naturally on tomato plants and are one of the most promising natural enemies for control of the tomato pest Aculops lycopersici (Acari: Eriophyidae). They also feed on fungi and have been demonstrated to control powdery mildew infections caused by Oidium sp. on tomato plants. However, it remains elusive how these predators control this disease and we therefore explored the mechanisms involved in this process. We show that powdery mildew is a suitable food source for Quasihomeopronematus nordestinus (Acari: Iolinidae), which can develop, survive and reproduce when feeding on it, much like on pollen, another excellent food source for the iolinid. Feeding on leaf tissue appeared to be obligatory for this predator, but did not allow for juvenile development and reproduction. Our findings indicate that consumption of the fungus is one of the mechanisms by which this iolinid mite suppresses powdery mildew infections in tomato plants.