The sec,ind plant diseases to be considered :Ire those 41111e to bacteria, over some of which there 11.1, been considerable controversy. Some writer, deny their bacterial origin. Ilia the investigations of [In. E. F. Smith and others seem to ',rote that in a number of well known instances bacteria are the immediate cause of di,ease. The.t investigators, by carefully conducted experiment-. have ,liereeded in pro. (luring the disca-c- in question by inoculation experiment, with the bacteria. 1)iseascs of fun gous origin for the most part attack certain defi nite portion, of plants. as the leaves. fruits. etc.. dest•oying them and indire, tly affecting the re-t if the plant : but the bacterial disca,es, upon soft. herbaceous plant, attack any part of the plant and eaii-c its sudden collapse without much delay. 'Prominent among the diseases at tributed to ba nay be mentioned the tire blight of and pears. black rot of cabbage. a wilt disease of cuenniber, and melon,. a brown rot of potatoes. egg-plant. and tomatoes. n disease of corn. a hyacinth di-ea-e, and a disease f celery. of these are fully characterized under their special the Of the third class may bementioned the Iillylloxera, which attack, the of tilt grape. IleV41-tating tile of Franee. Italy, and Europe generally, vt herever varlet ies of grape- which belong to a re grown : nematode, in orms. hich attack the root, of many plants in parts of •the United States. Europe, and elsewhere, causing galls to be formed to the "Feat detriment of the plant : and thrips and aphides. whose punctures a disease of and doubtless many The di-ease 4 f the la-t class are doe to some interfcreme with the proper exercise of the fune lion, of the plant—by improper nutrition. ton much or too little water, light. heat, etc. These manifest themselves in manner to the bacterial diseases, the whole plant being. affected. I'm• these diserse4 the correetive means suggest themselves, the only difficulty being the 41i-eotery of •'he investigation, of the pant few ye: have led to the ilkeovery not only of the valises of moan? plant (li:ea-•s, but al-, of the means where by they may be prevented. Cure, for such dis
eases are not known when the plant is once badly affected. so attention is given to their prevention. Sanitary conditions are necessary to keep plants in a healthy state. In order to prevent the spread of plant diseases, all affected plants and parts should be collected and burned. All weeds and wayside plants likely to harbor the disease should be destroyed. :\lany diseases are spread by in sects. and, as far as possible, these should be combated. :Nlany diseases may be prevented by the thorough and repeated spraying, of the plants with a fungicide (q.v.). The theory upon which these act is that the copper or other substances used are detrimental to the germination of the funr-u—spores by which the diseases are spread. Experience has shown that much of the loss due to sonic of our most common and destruetivc plant diseases might have •been absolutely pre vented by the timely and thorough use of fungi cides, and that at a cost very small indeed com pared to the loss sustained.
131BLIO6RAPill". Sirauer. Handbuch der Pflan zenkrankheiten (Berlin. 1S96 ) ; Frank, Die Krankhei t en (1. r Plla»:cn ( Tu beuf and Smith, The Diseases of Plants Induced by Cryptogamie Fungi (London. 1t:07) : Scrib ner, Fungus Disease.~ of the 4rape 11)7(1 Other Plants I Little Silver. N. .T.. IS90) : Lodeman, The Spraying of Plants (New York, 1896) ; see, A Textbook of Plant Diseases (London, 1:399): Hartig and Somerville, Discuses of Trees (London, 1594) ; Prillieux, ..1/a/adie• des plantes agrieolcs (2 vols., Paris. 1895-97) : publica tions of the United States Department of Agriculture, Division of Ve=etahle Pathology: also many of the reports and bulletins of agricultural experiment stations. For articles particularly relating to bacterial diseases, con sult: E. F. Smith, in American Naturalist (Philadelphia, IS9S-09) : Centralblatt fiir Bak teriologi( and Parasitenkunde, Ztreite Abtheilang (Jena, IS9S, et seq.). See FUNGICIDE: FUNGI,