. Biology of rust resistance in forest trees : proceedings of a NATO-IUFRO advanced study institute, August 17-24, 1969. Trees; Pine; Trees; Rust diseases. 366 R. T. BINGHAM Some improvement was obtained by: using inner chambers of poly- ethylene film; protecting outer rows of seedlings with paper or wet burlap barriers to prevent drying; maintaining standing water droplets on seed- lings by intermittent, hand misting (Fig. 5); and using R. hudsonianum leaf rather than R. visoossimum bush inoculum. Despite these improvements, given a really large test involving several contiguous chambers and
. Biology of rust resistance in forest trees : proceedings of a NATO-IUFRO advanced study institute, August 17-24, 1969. Trees; Pine; Trees; Rust diseases. 366 R. T. BINGHAM Some improvement was obtained by: using inner chambers of poly- ethylene film; protecting outer rows of seedlings with paper or wet burlap barriers to prevent drying; maintaining standing water droplets on seed- lings by intermittent, hand misting (Fig. 5); and using R. hudsonianum leaf rather than R. visoossimum bush inoculum. Despite these improvements, given a really large test involving several contiguous chambers and a warm inoculation season, fluctuations in levels of infection within and between the chambers have remained large. For instance, in 1966 when 800 running feet of nursery beds containing more than 75,000 seedlings were inoculated in three large, contiguous chambers (Fig. 1), it required almost 8 hours for a 6-man crew to lay out infected R. hudsonianwn leaves on screens suspended above the seedbeds (Fig. 6). The first of three chambers on the east was "buttoned up" at 10:00 and the last on the west at 3:00 , by which time some of the succulent R. hudsonianum leaves were wilting. During this inoculation ambient air temperatures reached 95°F, inner chamber temperatures 87°F. On the warmest afternoons a 3-man crew simply could not move fast enough with hand-mist nozzles to maintain water droplets on all seedlings. This is not surprising when one considers that at 50°F a cubic meter of saturated (100% ) air contains 9-1/2 gm of water, while at 86°F it contains 30-1/2 gm--or 3-1/4 times as much. Despite these problems, 3 years after this single, 72-hour inoculation, average level of infection in 10 "non-resistant" control lots of the main experiment was 88% (Table 1).. Figure 6. Infected Ribes hudsonianum leaves being laid out on inverted nursery bed cover screens, approximately 18 inches above pine seed- lings. Leaves from five or more different
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Keywords: ., bookauthoruni, bookcentury1900, booksubjectpine, booksubjecttrees
