Experiment Station Record, Volume 92, January-June, 1945 Page: 67
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1045] DISEASES OF PLANTS 67
During the last half of May, P. debaryanum became parasitic before and after
emergence, causing seed decay, stunted growth, and tip necrosis on the primary
and some of the seminal roots. As the season advanced and the soil temperature
was higher, P. graminicola became aggressive and induced a rapid necrosis on the
tips of most of the roots. At the same time G. saubinetii and R. -solani often
occurred on the lower part of the mesocotyl and later caused a discoloration and
necrosis of the roots. Later in the season other organisms such as H. sativum and
Penicillium oxalicunt produced further necrotic lesions on the mesocotyl and basal
portion of the roots. Still later in the sequence, Fusariumn spp., A. niger, T. lignorum,
and other saprophytic soil-inhabiting organisms were isolated from the root
and mesocotyl lesions; this group often developed extensively in the seedlings,
leaving no evidence of the organisms that had prevailed earlier.
Resistance of guayule to the root-knot nematode, W. G. HOYMAN. (Univ.
Ariz.). (Phytopathology, 34 (1944), No. 8, pp. 766-767).-Guayule transplants
were set out in the field and, greenhouse in soil known to be heavily infested with
Heterodera marioni. When grown as long as 19 mo. in such soil, the plants showed
only very slight infestation, indicating a high resistance to this nematode.
Experiments with pea seed treatments in Colorado, J. L. FORSBERG, E. OLSON,
and A. M. BINKLEY. (Colo. Expt. Sta.). (Phytopathology, 34 (1944), No. 8, pp.
753-759).-Treatment with Spergon, New Improved Ceresan, Arasan, or Yellow
Cuprocide usually gave increased stands in the three pea-growing sections where
tried. Although the first two gave best results in the majority of tests, stands and
yields varied in the different trials so that no one treatment was consistently outstanding.
Seed treatments were effective in preventing seed rotting but did not
protect plants from later attacks by root-rotting organisms. Isolations from diseased
plants showed that Fusarium solani martii f. 2, As'cochyta pinodella, Pythium
sp., and Corticium vlagum solani were present in Colorado soils.
Early harvesting of healthy seed potatoes for the control of potato diseases in
Maine, E. S. SCHULTZ, R. BONDE, and W. P. RALEIGH. (Coop. U. S. D. A.).
(Maine Sta. Bul. 427 (1944), pp. 19+).-When tubers were harvested from tuberunit
seed plots on successive dates the extent of spread of virus diseases increased
with time, there being little disease in stock harvested during July 25 through the
first week of August but usually a considerable amount in that lifted late in the
season. Tubers harvested by the first week of August were relatively free from leaf
roll, mosaic, and spindle tuber; when aphids were few or absent, very little infection
was found in those harvested the second week of August or even later. This earlyharvest
seed-plot method has been successfully employed with eight experimental
seed plots located in different parts of Aroostook County, and a number of farmers
have maintained high-quality seed potatoes by its use over 10-20-yr. periods. When
late blight is present, seed plots should not be harvested while the foliage is green.
Hand pulling is an effective though expensive method of killing the tops for the
early-harvest seed plot; in the work here described the tops were killed by spraying
with a solution of Sinox (2 gal.) and (NH4)2SO (10 lb.) in 100 gal. water. Treating
freshly dug tubers with a formaldehyde solution (1 pt. to 30 gal. water) or a
weak bordeaux (3-3-10a) greatly reduced the amount of late blight rot. If all
growers in potato regions would practice the method here described, it is believed
that ring rot would be eliminated and virus diseases controlled to such an extent
that epidemics would be very much reduced, if not prevented.
Relation of heat and desiccation to bacterial soft rot of potatoes, D. H. RosE
and H. A. SCHOMER. (U. S. D. A.). (Amer. Potato Jour., 21 (1944), No. 6,
pp. 149-161, illus. 2).-There is good evidence that bacterial soft rot-frequently
referred to as "sunscald"-in early and intermediate crop potatoes shipped directly
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U.S. Department of Agriculture. Agricultural Research Administration. Office of Experiment Stations. Experiment Station Record, Volume 92, January-June, 1945, book, 1947; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc5064/m1/80/: accessed December 16, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.