Temperature-manipulated dynamics and phenology ofMindarus abietinus(Hemiptera: Aphididae) in commercial Christmas tree plantations in Québec, Canada

Abstract

Abstract-The balsam twig aphid Mindarus abietinus Koch (Hemiptera: Aphididae) is a major pest of economic importance for the Christmas tree industry. Global warming during the 21st century could potentially increase local population densities and reinforce the pest status of this aphid in commercial fir (Abies Miller; Pinaceae) plantations in Québec, Canada. During this study, we tested the effects of a warmer environment on colony growth rates of M. abietinus and aphid morph composition during the second generation of its cycle, which is key to colony size growth and potential damage to Christmas trees. We monitored M. abietinus populations on two host fir species and one host fir variety, in order to understand the early season dynamics of this aphid and its host tree. It was possible to distinguish the two overlapping generations of winged aphids leaving colonies, which led to observing a much higher proportion of wingless daughters, produced by the stem mother, than what had previously been reported. Colony growth rates were significantly higher in a warmer environment than in the nearby plantation, suggesting that warmer temperatures in late spring and early summer may provide the suitable conditions required for M. abietinus colonies of greater density.Résumé-Le puceron des pousses du sapin Mindarus abietinus Koch (Hemiptera : Aphididae) est un ravageur d'importance économique en plantations commerciales d'arbres de Noël. Au 21 e siècle, le réchauffement climatique pourrait augmenter ses densités locales en plantation de sapin (Abies Miller ; Pinaceae) et renforcer son statut d'insecte ravageur au Québec, Canada. Nous avons testé expérimentalement les effets d'un environnement réchauffé sur la croissance des colonies de M. abietinus et le dimorphisme de progénitures de la fondatrice à la deuxième génération. Nous avons suivi les populations de M. abietinus sur trois arbres-hôtes du genre Abies, afin de mieux comprendre leurs interactions. Nous avons pu séparer les deux générations chevauchantes de pucerons ailés quittant les colonies, ce qui nous a permis d'observer une plus grande proportion de progénitures aptères de la fondatrice que dans les études antérieures. Le taux de croissance des colonies était plus élevé dans un environnement expérimental réchauffé que dans la plantation environnante, suggérant des conditions propices à des densités plus élevées de M. abietinus.

Embryonic stage of obligatory diapause and effects of abiotic conditions on egg hatching in the balsam twig aphid, Mindarus abietinus

“…Mindarus abietinus eggs are laid in early July and apparently stop developing in mid‐July, regardless of environmental cues, especially photoperiod, which is relatively stable shortly after the summer equinox in late June, but diminishes rapidly in late summer. This endogenous interruption of egg development in M. abietinus follows the production of the sexuales (i.e., males and oviparae) by the winged, parthenogenetic viviparous females, the sexuparae, which mature and disperse by flight in late June in Québec (Doherty et al., ). Hypothetically, the sexuparae could be the sensitive stage to the diapause‐inducing stimuli suggested by Tauber et al.…”

“…Partial prediapause embryogenesis in M. abietinus in the preceding summer may help explain their early hatching in May (Deland et al., ; Doherty et al., ), weeks before the spruce spider mite, Oligonychus ununguis (Jacobi), and the pine needle scale, Chionaspis pinifoliae (Fitch), two other known Christmas tree pests overwintering as eggs in southern Québec (Doherty et al., ). Prediapause development possibly is a specific adaptation of M. abietinus to its main host, the balsam fir.…”

“…Overwintering eggs, usually located near the base of fir needles, are deposited by sexually‐reproducing females in early July. These eggs survive the winter in obligatory diapause and complete embryogenesis to hatch only the following year in early May in southern Québec, Canada (Deland et al., ; Doherty et al., ).…”

Robust Model Predicts Shoot Phenology of Fraser Fir under Extreme Conditions

“…Understanding phenology is important for managing trees grown in plantations or forests. For example, both balsam gall midge (Paradiplosis tumifex Gagne) [6] and balsam twig aphid (Mindarus abietinus Koch) [6][7][8] cause economically significant damage to Fraser fir trees, but insecticides must be properly timed, based on insect and tree phenology, to provide acceptable control. Similarly, many Christmas tree producers in the southern Appalachians apply the herbicide glyphosate for weed suppression between rows of trees, in a process termed 'chemical mowing' [9].…”

“…Climate change is expected to usher in additional challenges [5]. Insect pest density is predicted to rise with the warming temperatures [8]. Early warming in the spring encourages a flush of tender growth that is sensitive to frost events later in the spring [12,13].…”