Experiment Station Record, Volume 74, January-June, 1936 Page: 58
xx, 1029 p. ; 24 cm.View a full description of this book.
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58 EXPERIMENT STATION RECORD [VoL 74
Phony peach disease control is promoted by destroying wild peach trees,
W. F. TURNER (U. S. Dept. Agr. Yearbook 1935, pp. 275-277).-An account is
given of an intensive compaign for the eradication of diseased wild peach trees
recently carried out in Georgia and Alabama.
A Phytophthora disease of peach seedlings, J. C. DUNEGAN (Phytopathology,
2'5 (1935), No. 8, pp. 800-809, figs. 2).-This paper reports the results of a
cooperative study by the Arkansas Experiment Station and the U. S. D. A.
Bureau of Plant Industry of a disease of peach seedlings in northwestern
Arkansas, differing in several respects from somewhat similar diseases previously
reported by others. It is characterized by the formation of a canker
on the succulent stems, followed by a red discoloration and rolling of the
terminal leaves, and, finally, by the wilting and death of the young trees in the
nursery rows.
From the cankers, appearing well above the soil line, a fungus identified as
P. cactorum was readily isolated and its pathogenicity proved in a series
of inoculation tests in which the disease was reproduced experimentally. The
fungus was found to invade the cortex and cambium tissues. Gum pockets are
formed in the region of the phloem, while the outer parenchyma tissues collapse
into a dark, discolored mass resting on the cortical fibers.
The prevalence of the disease is! correlated with periods of excessive rainfall
and cloudy weather during the early part of the growing season. Thus
far the only practical control measure has been to grow the seedlings in welldrained
sites.
In pure culture the fungus grows readily on standard media, producing
papillate sporangia from 30A to 45A long and from 24A to 36, in diameter
sympodially on slender sporangiophores. Antheridia, oogonia, and oospores
develop profusely on corn. meal agar and lima bean agar. The oogonia are
subspherical, from 321t to 38t in diameter; the oospores are thick walled, from
25, to 30/u in diameter; and the antheridia, which vary in shape from curved
tubes to spherical bodies, are predominantly paragynous. The organism grows
slowly at 5 C. and vigorously at from 21 to 26, but is inhibited at 32. On a
synthetic medium the fungus grew at from pH 4.0 to 9.0.--(Courtesy Biol.
Abs.)
A note on the recovery from silver-leaf disease of plum trees on common
plum and myrobolan stocks, respectively, F. T. BROOKS and G. H. BRENCHLEY
(Jour. Pomol. and Hort. Sci., 13 (1935), No. 2, pp. 135-139)..-This note records
the results of grafting and budding of plums of the Victoria variety on myrobolan
B (13 trees) and on common plum (15 trees) stocks, followed, when the
trees were 5 yr. old, by inoculating 3 of the larger shoots on each tree with
Stereunm purpureum. Three mo. after inoculation these shoots were all silvered
to about the same degree. Four yr. later the number of trees killed by silver
leaf, silvered, and healthy were, respectively, (1) for the trees on myrobolan
B, 4, 7, and 2, and (2) for those on common plum, 0, 3, and 12. Although the
high rate of recovery on the latter stock was probably related to the hot,
dry summers, of the last 2 yr., the difference in the course of the disease on the
2 stocks may be significant. It is thought that only by the accumulation of
such data that any definite statement can be made ultimately as to the influence
of the stock on the incidence of this disease of plum trees.
Seasonal relationship of dead twigs of citrus to stem-end rot, J. J.
TAUBENHAUS (Ann. Tex. Citrus Inst. Proc., 3 (1934), pp. 89-93; abs. in Texas
Sta. Cire. 76 (1934), p. 21).--Stem-end rot (Diaporthe citri and Diplodia
natalensis) was prevalent in the lower Rio Grande Valley during 1930c-31.
Both fungi were consistently isolated from dead citrus twigs and from the
rinds of grapefruits with stem-end: rot. Colletotrichum gloeosporioides and
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United States. Office of Experiment Stations. Experiment Station Record, Volume 74, January-June, 1936, book, 1937; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc5082/m1/78/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.