sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

SDÜ Faculty of Forestry Journal
eastern North America on native spruce species and on Norway spruce (Picea
abies (L.) H. Karst). Although sometimes numerous, these galls normally do not
seriously impact spruce health. They are, however, considered unsightly on trees
grown as ornamentals or as Christmas trees.
Although a single host species can support multiple generations of the Cooley
spruce gall adelgid, its complex life cycle normally involves alternation between
spruce and Douglas-fir hosts. The life history of this insect has been described in
detail by Cumming (1959) and summarized by the USDA Forest Service (1985).
Immature females overwinter as nymphs on the most recent year’s twigs of spruce.
After emergence and maturation in spring, the “stem-mother” deposits up to 350
eggs covered by a mass of white, waxy secretion. Eggs hatch in 1 to 2 weeks, and
nymphs feed at bases of new needles on the elongating shoots. Young, green to
purple, fleshy galls develop rapidly, elongating (up to 75 mm) and expanding in
girth (up to 18 mm) to enclose the feeding nymphs. By late summer galls open to
allow nymphs to move to needles where they molt into winged adults that fly to
Douglas-fir. On Douglas-fir the adelgid is able to reproduce parthenogenically and
sexually, overwinter as nymphs, and develop a winged stage that returns to spruce.
Although feeding occurs on Douglas-fir, galls similar to those on spruce are not
produced on this host.
Diplodia pinea (Desmaz.) J. Kickx fil. (syn. Sphaeropsis sapinea) is a widely
distributed, asexual fungal pathogen of conifers in native forests and where
planted as exotics (Punithalingam and Waterston, 1970). Reports of severe
damage caused by D. pinea most frequently involve pines (Pinus species),
especially two- and three-needled pines of the subgenus Diploxylon. However, the
fungus occasionally has been reported from spruce hosts or substrates (Farr et al.,
1989; Punithalingham and Waterston, 1970). Rain-splashed conidia of D. pinea
can be dispersed throughout the growing season (Palmer et al., 1988) and
germinate quickly followed by penetration directly (Brookhouser and Peterson,
1971; Chou, 1978) or through wounds. Disease may develop rapidly, or D. pinea
may persist on or in asymptomatic hosts (Stanosz et al., 2005) with subsequent
proliferation to cause disease under conditions that induce host stress (Stanosz et
al., 2001). Damage includes seed rot and seedling collar rot, shoot blight, branch
and bole cankers, crown wilt, and blue stain of sapwood (Chou, 1976; Chou, 1987;
Palmer, 1991; Rees and Webber, 1988; Stanosz and Cummings Carlson, 1996).
Diplodia pinea is frequently found sporulating on needles and stems it has killed,
and also on mature, opened seed cones (Waterman, 1943; Peterson, 1977).
Close examination of galls of the Cooley spruce gall adelgid from an
ornamental Colorado blue spruce revealed presence of pycnidia on the galls (and
attached needles) (Figure 1) that yielded D. pinea conidia. The objective of this
study was to examine the frequency of occurrence and amount of potential
inoculum of this pathogen from galls induced by the Cooley spruce gall adelgid.
Procedures used were modified from those developed by Munck and Stanosz
(2009) for water extraction of conidia from seed cones of pines.
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