File:Annual report of the Quebec Society for the Protection of Plants (1921-1935.) (18743341134).jpg

Title: Annual report of the Quebec Society for the Protection of Plants
Identifier: annualreportofqu1317soci (find matches)
Year: 1921-1935. (1920s)
Authors: Société de Québec pour la protection des plantes
Subjects: Plants, Protection of; Plants, Protection of; Plant diseases; Plant diseases
Publisher: Quebec : The Society
Contributing Library: New York Botanical Garden, LuEsther T. Mertz Library
Digitizing Sponsor: The LuEsther T Mertz Library, the New York Botanical Garden

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REPORT OF THE SOCIETY 73 available for tuber formation is reduced according to the severity of the disease and the duration of it in the particular plants. The tubers are therefore )-educed in size or in number, or both. In the case of late infection there is not likely to be any noticeable difference in the tubers. Murphy has estimated that severely diseased plants yield only 57.8 per cent of a crop as compared with healthy plants of the same variet)' under the same cultural conditions. Infection Gussow has shown that by grafting the disease maybe readily transmitted, acd Folsom et al. have obtained similar results in Maine. The writer in un- published work has found aphids to be fertile sources of infection, and Folsom et al. have carried on extensive experiments in Maine proving clearly that plant lice, (Myzus persicce Sulz. and Macrosiphum solamfolii Ashmead) are carriers of the disease from plant to plant. The writer has found that aphids are also most important in the transmission of clover mosaic and it is probable that they play a part in most mosaic diseases. Other potato pests, such as the Colorado potato beetle and the flea beetle, are not found to be carriers of the disease. Experiments also indicate that the seed cutting knife is not important in transmitting the disease. The same applies to contact in the field between healthy and diseased plants. Soil has not been found to transmit the disease from one season to the next, but it may be possible that volunteer plants arising from diseased tubers left in the soil will give rise to centres of infec- tion the following season. Varietal Susceptibility Little is yet known of this phase of the question and work on it is difficult because of the carrying over of diseased tubers which came from apparently healthy plants. It is known, however, that on the whole the Irish Cobbler variety is less susceptible to the disease while Green Mountain is particularly sus- ceptible. Control Three points in control are empha-
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T\g. 3—A leaf of potato showinis- mosaic mottling. Note at 1 a flea-bee'le hole and at 2 a typical light green area.

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