. Bacteria in relation to plant diseases. Bacteriology; Plant diseases. Fig. n: Methods of Prevention. In case of certain diseases, copper fungicides have been found useful, e. g., in walnut bacteriosis and some of the leaf spots, but in general we know as yet very little about bactericidal treatments. In the early stages of an outbreak some of these diseases may be controlled by extirpation of the affected parts, or by the removal of whole plants as soon as they show signs. Also, if possible, the common carriers of infection should be eliminated. Finally, one should not forget that the substi
. Bacteria in relation to plant diseases. Bacteriology; Plant diseases. Fig. n: Methods of Prevention. In case of certain diseases, copper fungicides have been found useful, e. g., in walnut bacteriosis and some of the leaf spots, but in general we know as yet very little about bactericidal treatments. In the early stages of an outbreak some of these diseases may be controlled by extirpation of the affected parts, or by the removal of whole plants as soon as they show signs. Also, if possible, the common carriers of infection should be eliminated. Finally, one should not forget that the substitution of resistant vari- eties for susceptible varieties is one of the most hopeful methods for disposing of certain of these vexatious diseases. Whenever any- thing specially noteworthy has been discov- ered in the way of treatment it will be mentioned under each particular Fig. *FiG. yj.—Bacterium cainpeslre from the cavity shown in fig. 76, illustrating water-pore infcL- tion of the cabbage. X 2,000. tFiG. 78.—Bacterium campcslre occupying a spiral vessel in a cahliage leaf near a group of infected water-pores. The tissues to the right and left of this \essel, and also above and below it (slide 223 a3, by ), are entirely free from bacteria. The body of the leaf and all its inner tissues up to within a few millimeters of the leaf-tooth, and also the outer surface of the leaf up to the water-pores, are sound. On the contrary, an unbroken bacterial occupation can be traced from this vessel outward to the water-pore region. The bacteria in this vessel are also less abundant than in those nearer to the group of water-pores, i. e., its occupation is of more recent date. Even if there were no other evidence of infection by way of the hydatodcs than that afforded by this vessel, the presence of the bacteria in it under the circumstances mentioned points conclusively to marginal (water-pore) infection as their only possible source. The position of this ves
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