Summary: 1. Indirect induced plant defence via emission of herbivore‐induced plant volatiles (HIPV) to recruit natural enemies of herbivores is a ubiquitous phenomenon, but whether and how emission of above‐ground HIPVs is adaptively modulated by below‐ground mutualistic micro‐organisms is unknown.2. We investigated the effects of the mycorrhizal fungus Glomus mosseae on chemical composition of HIPVs emitted by bean plants Phaseolus vulgaris attacked by spider mites, Tetranychus urticae, using proton‐transfer mass spectrometry, and attraction of the spider mites’ natural enemy, the predatory mite Phytoseiulus persimilis, to these HIPVs using a Y‐tube olfactometer.3. Mycorrhiza significantly changed the HIPV composition. Most notably, it increased the emission of β‐ocimene and β‐caryophyllene, two compounds synthesized de novo upon spider mite attack. The constitutively emitted methyl salicylate was increased by spider mite infestation but decreased by mycorrhiza.4. The predators responded strongly to HIPVs emitted by plants infested for 6 days and preferred HIPVs of mycorrhizal plants to those of non‐mycorrhizal plants. In contrast, they were less responsive and indiscriminative to mycorrhization when exposed to volatiles emitted by non‐infested plants and plants infested by spider mites for 1 or 3 days.5. Our study provides a key example of an adaptive indirect HIPV‐mediated interaction of a below‐ground micro‐organism with an above‐ground carnivore.

We tested 13 species of phytoseiid mites for prey preferences between eggs and larvae of twospotted spider mite, Tetranychus urticae Koch. In general

Coconut is an important crop in tropical and subtropical regions. Among the mites that infest coconut palms,Aceria guerreronisKeifer is economically the most important. We conducted surveys throughout the coconut growing areas of Brazil. Samples were taken from attached coconuts, leaflets, fallen coconuts and inflorescences of coconut palms in 112 localities aiming to determine the occurrence and the distribution of phytophagous mites, particularlyA. guerreronis, and associated natural enemies.Aceria guerreroniswas the most abundant phytophagous mite followed bySteneotarsonemus concavuscutumLofego & Gondim Jr. andSteneotarsonemus furcatusDe Leon (Tarsonemidae). Infestation byA. guerreroniswas recorded in 87% of the visited localities. About 81% of all predatory mites belonged to the family Phytoseiidae, mainly represented byNeoseiulus paspalivorusDe Leon,Neoseiulus barakiAthias-Henriot andAmblyseius largoensisMuma; 12% were Ascidae, mainlyProctolaelaps bickleyiBram,Proctolaelapssp nov andLasioseius subterraneusChant.Neoseiulus paspalivorusandN. barakiwere the most abundant predators on attached coconuts. Ascidae were predominant on fallen coconuts, whileA. largoensiswas predominant on leaflets; no mites were found on branches of inflorescences. Leaflets harboured higher mite diversity than the attached coconuts. Mite diversity was the highest in the state Pará and on palms surrounded by seasonal forests and Amazonian rain-forests.Neoseiulus paspalivorus,N. barakiandP. bickleyiwere identified as the most promising predators ofA. guerreronis. Analyses of the influence of climatic factors revealed that dry ambient conditions favour the establishment ofA. guerreronis. Neoseiulus paspalivorusandN. barakihave differing climatic requirements; the former being more abundant in warm and dry areas, the latter prevailing in moderately tempered and humid areas. We discuss the significance of our findings for natural and biological control ofA. guerreronis.