Mites affect plum curculio (Coleoptera: Curculionidae) behavioural responses to attractive volatiles Virginia Hock, 1 Ge ´rald Chouinard, E ´ ric Lucas, Daniel Cormier Abstract—An infestation of Histiostoma Kramer sp. mites (Acari: Histiostomatidae) occurred in rearing colonies of the univoltine strain of plum curculio (PC), Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), established in 2010 in southern Que ´bec, Canada. Tests conducted in a two-choice still-air vertical olfactometer with mite-infested and noninfested PC revealed that the number of beetles responding by walking towards normally attractive synthetic and natural odours was significantly lower for those infested with mites. Those mite-infested curculios that did discriminate between test odours and odour-free air all responded positively to the test volatiles, similar to the behaviour of noninfested insects. This indicates that mites affect PC ability to physically move towards attractive volatiles but not odour preference. Re ´sume ´—Une infestation par les acariens phore ´tiques du genre Histiostoma Kramer (Acari: Histiostomatidae) s’est produite dans l’e ´levage de la souche univoltine du nord du charanc ¸on de la prune Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae) e ´tablie en 2010 dans le sud du Que ´bec, Canada. Des tests ont e ´te ´ effectue ´s a ` l’aide d’un olfactome `tre vertical a ` deux-voies, sans pression d’air. Les charanc ¸ons infeste ´s et non-infeste ´s ont e ´te ´ teste ´s et ont re ´ve ´le ´ un effet des acariens sur la re ´ponse olfactome ´trique de cet insecte. Pour les odeurs synthe ´tiques et naturelles attractives aux charanc ¸ons, significativement moins de charanc ¸ons infeste ´s par des acariens ont re ´pondu aux odeurs que de charanc ¸ons non-infeste ´s. Pour cette raison, l’attraction des charanc ¸ons infeste ´s par des acariens vers les sources des odeurs e ´tait difficile a `e ´tablir. Cependant, tous les charanc ¸ons infeste ´s ayant re ´pondu ont re ´agit positivement aux volatiles teste ´s, d’une fac ¸on similaire aux insectes non-infeste ´s. Ceci indique que les acariens affectent la capacite ´ des charanc ¸ons a ` re ´pondre aux volatiles attractifs mais n’affectent pas leurs pre ´fe ´rences. Mites have been known to infest plum curculio (PC) Conotrachelus nenuphar (Herbst) (Coleop- tera: Curculionidae) larvae and adults (Smith 1957; Broersma and Hays 1966; Amis and Snow 1985), and impair movement of this and other species of insects (Amis and Snow 1985; Smith 1988). We conducted olfactometric bioassays to determine if mite-infested PC adults behave differently than noninfested PC regarding response to volatiles. Apples containing PC larvae were collected from the field in 2009 in Saint-Bruno-de-Montarville, Que ´bec, Canada (45.550288N, 73.319178W) during June drop and placed in emergence cages. Emer- ging nonsexually mature adults were collected daily and immediately separated by sex (Thompson 1932) and transferred to overwintering cages (Le Blanc 1992) and placed outdoors under natural conditions throughout the winter. Overwintered adults were removed from their cages the following V. Hock, 1 Institut de recherche et de de ´veloppement en agroenvironnement (IRDA), Laboratoire de Production Fruitie `re Inte ´gre ´e 335, chemin des Vingt-Cinq Est Saint-Bruno-de-Montarville, Que ´bec, J3V 0G7 Canada; and Universite ´ du Que ´bec a ` Montre ´al (UQAM), De ´partement des sciences biologiques, Laboratoire de lutte biologique, Case postale 8888, succursale Centre-ville, Montre ´al, Que ´bec, H3C 3P8 Canada G. Chouinard, D. Cormier, Institut de recherche et de de ´veloppement en agroenvironnement (IRDA), Laboratoire de Production Fruitie `re Inte ´gre ´e 335, chemin des Vingt-Cinq Est Saint-Bruno-de-Montarville, Que ´bec, J3V 0G7 Canada E ´ . Lucas, Universite ´ du Que ´bec a ` Montre ´al (UQAM), De ´partement des sciences biologiques, Laboratoire de lutte biologique, Case postale 8888, succursale Centre-ville, Montre ´al, Que ´bec, H3C 3P8 Canada 1 Corresponding author (e-mail: virginia.hock@irda.qc.ca). doi:10.4039/tce.2012.94 Received 11 April 2012. Accepted 18 June 2012. Can. Entomol. 145: 82–87 (2013)  2013 Entomological Society of Canada 82