Jl. Jenkinson et Ah. Mccain, WINTER SOWINGS PRODUCE 1-0 SUGAR PINE PLANTING STOCK IN THE SIERRA-NEVADA, USDA Forest Service research paper PSW, (219), 1993, pp. 210000001-10
Seed source and sowing date effects on first-year seedling growth and
Fusarium root and collar rot of sugar pine were analyzed in two consec
utive nursery tests at the Pacific Southwest Research Station's Instit
ute of Forest Genetics, near Placerville in the western Sierra Nevada.
The experimental design in both tests consisted of four replications
of a randomized complete block of split-split plots, with sowing date
split for disease treatment and seed source. Seed sources were natural
stands at low, middle, and high elevations on the western slope of th
e northern Sierra Nevada. Seeds were soaked 36 hours in aerated water
at 25-degrees-C (77-degrees-F), chilled 90 days at 1-degrees-C (34-deg
rees-F), and sown in fumigated soil in February, March, April, and May
. Treatment plots were drenched with fungicides just before sowing in
the first test, and were inoculated with Fusarium oxysporum f. sp. pin
i at time of sowing in the second test. Seedling emergence averaged 96
to 99 percent, regardless of sowing date. Seedlings in February sowin
gs reached triple the size of those in the traditional May sowings, an
d mortality in the check and inoculated plots averaged 3 and 6 percent
in the February sowings, against 17 and 33 percent in the May sowings
. The results show that seedlings in early sowings (February, March) c
onsistently escape Fusarium disease and produce 1-0 planting stock. Th
ose in late sowings are highly susceptible to Fusarium and the survivo
rs must be carried through a second growing season to produce 2-0 plan
ting stock.