lUL'O] DISEASES OF PLANTS. 551 



niont of Agriculture, tlu> author lias (•l)tiiiiiod oxinTimeiital evidence to slinw 

 Ihat l'scu(1omona>i cilii (lisai)itciirs from uustorilized soil in tubes and box(>s 

 usually within six days after tliey are inoculated. P. citri inoculated in steri- 

 lized soil increases and multiplies. The disappearance of P. citri in uiisterili7>'d 

 soil is believed 'to be attributable to the antagonistic effect of other soil 

 orgaidsms. Under orchard conditions the canker organism was found to dis- 

 appear even more readily than in soil confined in boxes or culture tubes. 

 Seeds planted in pots of soil naturally infected with the canker organism and 

 in pots artlticially inoculated developed normally without any caid<er. indi- 

 cating that the canker bacteria had in some way been killed in the normal 

 soils. Buried leaves and mature wood and roots are believed to be possible 

 sources of holding over the canker organism. 



Decline o£ Pseiidomoiias citri in the soil, H. R. Fulton {Jour. Agr. Re- 

 search [U. &.], 19 {1920), No. 5, pp. 207-223).— In a contribution from the Bu- 

 reau of Plant Industry, U. S. Department of Agriculture, results are given of 

 an investigation to determine whether or not the citrus canker organism 

 {P. citri) is capable of persisting in the soil to such an extent as to make the 

 soil an important medium in holding over or disseminating the organism. 



Tests on many types of soils showed a rapid decline of P. citri in all. This 

 decline was retarded slightly by rendering the soil alkaline with lime water or 

 by lowering its temperature, and more decidedly by withholding water or by 

 previous sterilization with steam. Extremely long persistence in small num- 

 bers was noted in soil held in air-dry condition. P. citri was found to pene- 

 trate tlie soil to depths ordinarily cultivated, but the normal decline seemed 

 to occur at such depth. In water the decline was more rapid than in soil, but 

 previous sterilization of w\iter had a decided effect in prolonging resistance. 

 ( 'ertain bacteria commonly found in soils are said to have a marked deleterious 

 I'tYect on P. citri in artificial culture media, and the presence of such organisms 

 in soil is believed to be concerned in producing a decline of P. citri. Young 

 roots of grapefruit seedlings did not seem to he readily infected except through 

 wounds. 



Control of root knot by calcium cyanamid, .1. R. Watson {Proc. Fla. 

 State Hort. Soc, SO {1917), pp. 27-.?//). — A more extended account of these ex- 

 periments has been noted (E. S. R., 37, p. 453). 



Scaly bark, a disease of citrus trees, C. D. Kime {Proc. Fla. State Hort. 

 Soc, 31 {1918), pp. 86-89). — Citrus scaly bark {Cladosporiiiin hcrbarum citri- 

 colum) outbreaks are said to have been reported for 11 counties, representing 

 many prominent citrus sections of Florida. An account is given of the out- 

 breaks, effects, and efforts at control. 



Coconut bud rot, J. A. Stevenson (Rev. Agr. Puerto Rico, 2 (1918), No. 1, 

 pp. '19, 50). — A rapidly progressing tiud rot of coconut is said to be caused by 

 Bacillun coli. 



Correspondence relating to coconut diseases occurring in Grenada 

 ([/»»p. Dcpt. Agr. West Iiidies] [Pamphlet], 1918, pp. 6). — The chief particu- 

 lars in this correspondence regarding coconut diseases are furnished by W. 

 Nowell, who reports on a visit to Grenada in October, 1918, to investigate 

 diseases of coconut. 



Besides bud rot, three other local diseases are distinguished, namely, little 

 leaf disease, root disease,_and a condition of debility associated with water- 

 logging, severe root competition, or soil exhaustion. These are discussed in 

 connection with remedial measures. Nematodes are found in connection with 

 the root disease here noted, and with the disease locally called bluggoes. 



