Oct. IS, I92I Transmissible Mosaic Disease of Cabbage 175 



a plant of the same or a closely related species.^ No mosaic mottling 

 appeared on any of the cruciferous plants inoculated with juice from 

 mosaic potato. With a more adequate supply ofcrucifer mosaic mate- 

 rial and repeated applications it is probable that every plant treated 

 would have developed mosaic mottling, such as has frequently been 

 obtained with mosaic potato juice inoculations on the Irish potato.^ 



The first mosaic mottling was observed from 20 to 30 days after inoc- 

 ulation, which also corresponds very closely with the incubation period 

 for mosaic of Irish potato. The results in Table I also disclose successful 

 inoculations on plants in different species of Brassica. Further evidence 

 on this interspecific infection is presented in Table II on transmission by 



means of aphids. 



TRANSMISSION WITH APHIDS 



Since aphids were found on every mosaic plant examined in the field 

 and on account of the fact that these insects have been found to transmit 

 mosaic of tobacco,^ spinach blight/ and mosaic of potato,'' experiments 

 were carried on with these insects. Aphids belonging to Myzus persicae 

 Sulz. were used in this investigation. These insects were originally 

 collected from the morning-glory and transferred to healthy turnip and 

 mustard plants on which they were cultured while confined under cages 

 until needed for inoculation. Neither the morning-glory nor the turnip 

 or mustard plants on which these insects fed before being transferred 

 to mosaic Chinese cabbage and turnip developed mosaic mottling. 

 This indicates that the morning-glory apparently was free from mosaic, 

 at least from the type which could infect the crucifers used in this 

 experiment. 



When the healthy plants for inoculation had developed from five to 

 eight leaves, aphids were transferred from the cultures to mosaic plants, 

 where they were allowed to feed for a few days before they were intro- 

 duced to the healthy plants. All inoculated plants also were confined 

 in cages so as to prevent dispersal from one species to another. After 

 the aphids had fed from 7 to 14 days on the inoculated plants they were 

 killed by tobacco fumigation in a fumigation chamber. These plants 

 were now allowed to grow without cages in a greenhouse where fumiga- 

 tion was practiced at regular intervals for the control of aphids. Since 

 mosaic mottling developed from 12 to 30 days after these insects were 

 killed by fumigation, mosaic mottling can not be attributed simply to 

 the mechanical injury produced by the aphids. This fact is further 



J Gardner, Max W., and Kendrick, James B. turnip mosaic. In Jour. Agr. Research, v. 22, no. 3, 

 p. 123-124, I pi. 1921. 



- ScHXJLTz, E. S., Foi^oM, Donald, Hudebrandt, F. Merrill, and Hawkins, I,on A. op. ot. 



' Allard, H. A. THE MOSAIC disease OF TOBACCO. U. S. Dept. Agf. Bul. 40, 33 p. , 7 pi. 1914. 



* McCuNTOCK, J. A., and Smith, Loren B. true nature of spinach-blight and relation of insects 

 TO ITS transmission. In Jour. Agr. Research, v. 14, no. i, p. 1-60, pi. A (col), i-ii. 1918. 



6 Schultz, E. S., Folsom, Donald, Hildebrandt, F. Merrill, and Hawkins, Lon. A. op. ciT. 



