Autumnal recruitment of mite's predators by herbivore-induced plant volatiles in avocado (Persea americana Mill. cv. Hass) infested with Oligonychus yothersi (Acari: Tetranychidae)

The red mite, Oligonychus yothersi (McGregor) (Acari: Tetranychidae), is a serious foliar pest of avocado (Persea americana Mill.) orchards in Chile. In summer, avocado plants release herbivore-induced plant volatiles (HIPVs) in response to feeding behaviour of O. yothersi. These HIPVs recruit natural enemies of the red mite as Parastethorus histrio (Chazeau) (Coleoptera: Coccinellidae) and Oligota pygmaea (Solier) (Coleoptera: Staphylinidae). However, P. histrio and O. pygmaea remain in infested avocado trees throughout the summer until late autumn. Therefore, we collected HIPVs, in late autumn, to test the behavioural responses of the red mite and its coleopterans predators. Volatiles were collected under semi-field conditions using the headspace technique and Porapak Q as adsorbent. The chemical analysis revealed that infested plants emitted (Z)-beta-ocimene, alpha-farnesene, and methyl salicylate (MeSA), increasing the emissions of R-limonene. These variations triggered an attractive behaviour in P. histrio and O. pygmaea, yet O. yothersi remained indifferent. The emitted HIPVs by avocado infested plants, in late autumn, elicited tri-trophic interactions in avocado orchards, where higher R-limonene emissions and up-regulated three new volatile compounds in the volatiles profile could have influenced predator's choice, being necessary to examine.