. Recent research on foliage diseases : conference proceedings : Carlisle, Pennsylvania, May 29-June 2, 1989. Leaves Diseases and pests United States Congresses. 1982 1983 Figure 1.—Percentages of Rhabdocline pseudotsugae subsp pseudotsugae asci which contained ascospores, cytoplasm, or were empty and daily maximum-minimum temperatures and precipitation during 1982 and 1983. Identification of infection periods.—By comparing the disease ratings for trees receiving various system- atic fungicide applications during 1982 and 1983, we found that the majority of infections occurred during shoot elo
. Recent research on foliage diseases : conference proceedings : Carlisle, Pennsylvania, May 29-June 2, 1989. Leaves Diseases and pests United States Congresses. 1982 1983 Figure 1.—Percentages of Rhabdocline pseudotsugae subsp pseudotsugae asci which contained ascospores, cytoplasm, or were empty and daily maximum-minimum temperatures and precipitation during 1982 and 1983. Identification of infection periods.—By comparing the disease ratings for trees receiving various system- atic fungicide applications during 1982 and 1983, we found that the majority of infections occurred during shoot elongation from late May through mid-June in 1982 and during late May in 1983. Trees which did not receive protective sprays between 19 May and 16 June in 1982 and 19-25 May in 1983 had disease ratings which were not significantly different from the nonsprayed checks (table 1). During these infection periods, shoots elongated from 3 to 11 cm in 1982 and to cm in 1983 (table 1). Effectiveness of various fungicides.—In 1982, three applications of either benomyl, mancozeb or chlorothalonil provided effective disease control (table 2). There was no significant difference in the level of disease control obtained between any of the materials tested, and doubling the rates did not improve the level of disease control (data not shown). In 1983, single and double applications of these three fungicides were tested. Disease pressure was lower in 1983 than 1982 and a single application of mancozeb at gm a. or chlorothalonil at gm a. i/1 significantly reduced the level of disease compared to the nonsprayed check (table 3). The early single application of these fungi- cides was as effective as two applications of these materials at lower rates under this low disease pressure (table 3). During 1983, a single application of beno- myl at gm a. was not effective and two applica- tions at lower rates were only moderately effective (table 3). Discussion When the
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