Germination, penetration, and infection by Arceuthobium americanum on Pinus banksiana

Abstract

Information on the establishment of Arceuthobium americanum Nutt. ex Engelm. on its host, jack pine (Pinus banksiana Lamb.), is required to improve knowledge of this critical development stage and improve pest management. Laboratory and field observations on four populations of A. americanum seeds from Alberta collected in 2000 and 2001 and histological observations on one population were used to determine the timing and histopathology of parasite establishment on jack pine. Seed germination remained near zero until 110 d after placing seeds in storage; germination peaked after 230 d in 2001 and between 230 and 320 d in 2002. Interannual variation in germination timing at study sites was high. Interannual variation in percentage of germination was low, as was variation in percentage of germination from different seed sources. Germinated seeds of each seed source were significantly larger (48%) than seeds that did not germinate. Penetration at the base of spur shoots began during June-August and usually continued until June-July of the next year. The odds of infection when the germinant survived until the second growing season were 26-55 times greater than the odds of infection when the germinant withered in the first growing season. Symptoms of infection usually occurred 13-15 months after germination and were consistent for all seed sources and sites. Résumé: Il est nécessaire d'acquérir de l'information au sujet de l'établissement d'Arceuthobium americanum Nutt. ex Engelm. sur son hôte, Pinus banksiana Lamb., pour avoir une meilleure connaissance de ce stade critique de dévelop-pement et améliorer la gestion des ravageurs. Des observations en laboratoire et sur le terrain portant sur quatre populations de graines d'A. americanum, faites en 2000 et 2001 en Alberta, et des observations histologiques dans une population ont servi à déterminer le moment et l'histopathologie de l'établissement de ce parasite sur le pin gris. La germination des graines est demeurée presque nulle jusqu'à 110 j après que les graines eurent été entreposées. Elle a atteint un sommet après 230 j en 2001 et entre 230 et 320 j en 2002.La variation dans le moment de la germination était élevée dans les sites à l'étude. La variation interannuelle du pourcentage de germination était faible, ainsi que la variation dans le pourcentage de germination entre les différents lots de graines. Dans chaque lot de graines, les graines qui ont germé étaient significativement (48 %) plus grosses que celles qui n'ont pas germé. La pénétration à la base des branches fruitières commençait en juin-août et continuait habituellement jusqu'en juin-juillet de l'année suivante. Lorsque le germinat survivait jusqu'à la deuxième saison de croissance, les chances d'infection étaient 26-55 fois plus élevées que s'il flétrissait durant la première saison de croissance. Les symptômes de l'infection apparaissaient habituellement 13-15 mois après la germination et étaient consistants pour tous les lots de graines et tous les sites.[Traduit par la Rédaction] Brandt et al. 1...

Mountain pine beetle associated blue-stain fungi cause lesions on jack pine, lodgepole pine, and lodgepole × jack pine hybrids in Alberta

“…Other pests could influence the susceptibility of pine stands to MPB attack. Dwarf mistletoe (Arceuthobium americanum Nuttall ex Engelmann) is one of the most damaging pests of lodgepole and jack pines in western Canada (Brandt et al 2005). Interactions between dwarf mistletoe and MPB have been suggested for lodgepole pine (Hawksworth et al 1983); however, empirical evidence is equivocal, with some studies suggesting that mistletoe-infected trees are more susceptible to MPB attack, others suggesting that they are less susceptible, and some studies suggesting no relationship (see Hawksworth et al 1983 for a discussion).…”

Callus Culture of Arceuthobium americanum Nutt. ex Englem. and Explant Response to Varying Auxin and Cytokinin Concentrations

“…When Arceuthobium americanum infects lodgepole pine, it induces the formation of witches' brooms (Tinnin et al 1982, Brandt et al 2005. Additionally, Schaffer et al (1983) have shown that witch's broom formation in ponderosa pine (Pinus ponderosa Dougl.…”

“…The parasite is dependent on its host for water, minerals and some photosynthate; as such, A. americanum specimens live only a short time without their host plant (Brandt et al 2005). Cut pine branches infested with mistletoe are only viable for a few days at room temperature and a month at most at 4°C.…”