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Percentages of Douglas-fir trees 20 cm diameter at breast height mass attacked by
Douglas-fir beetle were significantly lower on plots treated with dispensers eluting 2 and 6 mg/d
and spaced 5 and 15 m apart, respectively, compared with the untreated control. Infestation rate
on plots treated with dispensers eluting 18 mg/d and spaced 44 m apart was not significantly
different from the control. Douglas-fir beetle abundance and host tree availability were similar on
all plots. These results indicate that MCH dispensers eluting 6 mg/d (three times the current
standard rate) and spaced 15 m apart (three times existing standard distance) can effectively
prevent Douglas-fir beetle infestations.
520. Ross, D.W., K.E. Gibson, R.W. Thier and A.S. Munson. 1996. Optimal dose of an
antiaggregation pheromone (3-methylcyclohex-2-en-1-one) for protecting live Douglas-fir from
attack by Dendroctonus pseudotsugae (Coleoptera: Scolytidae). Journal-of-Economic-
Entomology 89(5): 1204-1207.
Keywords: tree/stand protection
tree/stand health
stand conditions
Abstract: The Dendroctonus pseudotsugae antiaggregation pheromone, 3-methylcyclohex-
2-en-1-one (MCH), was applied to stands of Douglas fir, Pseudotsuga menziesii in Oregon,
Montana, Idaho and Utah, at high risk for infestation to determine the lowest effective dose for
protecting live trees. MCH was applied at rates of 50, 100, and 150 bubble capsules per hectare
(20, 40, and 60 g/ha, resp.) in 1994, and 15, 30, and 50 bubble capsules per hectare (6, 12, and 20
g/ha, resp.) in 1995. Mean release rates throughout the beetle flight periods in 1994 and 1995
were 1.63 and 1.23 milligrams per capsule per day, resp. For both years, catches of Douglas fir
beetles in pheromone-baited traps located at the plot centers were significantly lower on all
MCH-treated plots compared with untreated plots, but there were no differences among the 3
doses of MCH. In contrast, MCH had no effect on the numbers of 3 predators (Thanasimus
undatulus, Enoclerus sphegeus and Temnochila chlorodia [Temnoscheila chlorodia]) collected in
the traps during either year. In 1994, the percentage of Douglas fir 20 cm diameter at
breast height (dbh) that were mass attacked was significantly lower on MCH-treated plots
compared with the untreated control, and all 3 doses were equally effective. In 1995, there were
no significant differences in the percentage of mass-attacked trees among the treatments. These
results demonstrate that MCH applied at rates as low as 20 g/ha (50 bubble capsules per hectare)
can reduce the probability that high-risk Douglas fir will become infested.
521. Ross, S.D. and R.C. Bower. 1989. Cost-effective promotion of flowering in a Douglas-fir seed
orchard by girdling and pulsed stem injection of gibberellin A4/7. Silvae-Genetica 38(5-6): 189-
195.
Keywords: seed orchard management
reproduction
economics
Abstract: In a seed orchard in British Columbia, Canada, Douglas fir (Pseudotsuga
menziesii) grafts of 5-14 cm diam. received different combinations of partial saw-cut stem girdles
and ethanolic solutions of GA4/7 injected into shallow holes drilled around the main stem. Grafts
averaged 79 seed-cone buds and 4500 pollen-cone buds each without treatment. Girdling alone
increased production per tree of seed- and pollen-cone buds to 325 and 9300 respectively. GA4/7
alone was nearly as effective as girdling alone, the response being marginally greater at the high
than low dosage (3.82 vs. 1.27 mg/cmsuperscript 2 of stem cross sectional area), but independent