Report on the Agricultural Experiment Stations, 1952 Page: 56
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56 REPORT ON EXPERIMENT STATIONS, 1952
The Maryland station (coop. USDA) found that the tobacco mosaic
virus is widely distributed throughout the tobacco-producing areas
of the State and that it may be carried back to the land by the application
of unsterilized stems and waste leaf scraps as a fertilizer or
soil conditioner. Tests indicate, however, that the virus in tobacco
stems can be inactivated by exposure for 15 minutes or longer to a
temperature of 212 F. in a saturated atmosphere.
By fall plowing or by leaving the land out of tobacco for a year
or more, the Connecticut station drastically reduced tobacco mosaic.
This indicates that cultural methods can do much to control some of
the more serious diseases of tobacco. The use of soil fumigants in
areas heavily infested with nematodes added from $75 to $140 per
acre to the value of tobacco, according to the North Carolina station.
Fire blight may lose its burn
The Colorado, Missouri, and Arkansas stations report that fire
blight, one of the most troublesome diseases of apples and pears, may
lose some of its potency. The Colorado station found that spraying
Dithane Z-78 in the 10-percent bloom and again in full bloom reduced
the incidence of current season blossom and twig infection approximately
75 percent. This spray method, together with sanitary
pruning and treatment of hold-over cankers, has become standard
practice in fire blight control in Colorado.
Infections were markedly reduced on apple trees in full bloom
sprayed with streptomycin or thiolutin, according to a Missouri report.
Calcium hypochlorite, a very commonly used laboratory disinfectant,
was found by the Arkansas station to be equally as effective in controlling
fire blight as bordeaux mixture, and it did not russet the
A technique for maintaining virulent cultures of the fire blight
organism was found by the Illinois station which should facilitate
further studies of the disease. It was observed that the fire blight
bacterium was able to survive over winter in mummied pear fruit.
By inoculating pears with pure cultures of the organism and placing
them in a refrigerator maintained at 5 C., a virulent culture of the
fire blight bacterium could be isolated for tree inoculations in the
Better control of row crop foliar diseases
Many vegetable growers are still waiting for more efficient concentrate
spraying methods to be developed for the control of foliar diseases
in row vegetable crops. The Ohio station has carried on research
designed to determine additional details on the technique of
spray application under practical field conditions. It was found that
2X and 4X spray concentrations applied at 40 and 80 gallons gave
approximately as good control of foliar diseases of tomatoes as did
a 1X concentration at 160 gallons per acre.
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United States. Office of Experiment Stations. Report on the Agricultural Experiment Stations, 1952, book, January 1953; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc5990/m1/58/: accessed July 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.