DISEASES OF PLANTS. 239 



The spread of the celery leaf spot disease by the use of affected seed, and 

 its prevention, G. H. Pethybridge (Dept. Agr. and Tech. Instr. Ireland Jour., 

 14 (1914), No. Jf, pp. 687-69Jf, pi. 1). — This is an account of investigations re- 

 garding the propagation and control of Septoria petroselini apii on celery. 



Tests were made with 109 samples of celery seed representing all common 

 vax'ieties obtained from dealers, 92 itev cent of the samples showing the presence 

 of the fungus. Tests for germinability of the spores present on the seeds 

 showed a low rate which, however, might cause a high degree of infection when 

 seeds are sown thickly, as is common in practice. 



Tests with fungicides are described, from which it was found that infected 

 seed are rendered safe, without serious injury to germinability, by immersion 

 for three hours in hydrogen peroxid or formalin with or without one hour's 

 previous soalcing in water. Immersion in 2 per cent copper sulphate for 24 

 hours seriously impaired germinability. 



Investigations on potato diseases (fifth report), G. H. Pethtbridge (Dept. 

 Agr. and Tech. Instr. Ireland Jour., 14 {1914), No. 3, pp. 433-455, pis. 3; abs. 

 in Jour. Bd. Agr. [London], 21 {1914), ^0. 4, pp. 342-344). — Continuing previous 

 communications (E. S. R., 29, p. 549), the author reports on several potato 

 diseases. 



As regards potato blight {Phytophthora infestans), it is stated that while 

 results of spraying experiments may have been vitiated by weather conditions 

 in 1913, spraying just before the beginning of unfavorable weather gave the 

 best results, as in previous years. Spraying from below seemed superior to 

 that from above. Burgundy mixture seemed on the whole superior to Bordeaux 

 mixture, and fungicidal powders appeared to be inferior to sprays. 



Stalk disease {Sclcrotinia sclerotiorum) was best controlled by late planting, 

 the best results being obtained from planting about May 15. Black stalk rot 

 {Bacillus melanogenes) was less abundant on the hardier plants from seedings 

 of May and June than fi-om those of March and April. 



Regarding corky or powdery scab {Spongospora suMerranea) , it is said that 

 among the varieties tested for several years there is not one which shows a 

 constant tendency to resist the disease. Treatment of the soil with a mixture 

 of ammonium sulphate and quicklime at the rate of 30 and 15 lbs., respectively, 

 per square rod reduced the disease somewhat. 



Pink rot and wilt are both claimed to be due to P. eryihroseptica, which can 

 attack the plant directly from the soil, possibly not through seed potatoes. 



Investigations are claimed to show that a specific Verticillium disease of 

 pototo exists. 



Potato diseases — the dang'er of importation, C. C. Brittlebank {Jour. 

 Dept. Agr. Victoria, 12 {1914), No. 7, pp. 400-403).— It is stated that the only 

 important new disease of the potato appearing in Australia since 1911 is that 

 known as scurf or dry scab, due to Spondylocladium atrovirens. Consignments 

 of imported potatoes examined showed an abundance of disease present in most 

 cases. One shipment, said to be fairly representative, contained Spongospora 

 subterranea, Phytophthora infestans, Rhisoctonia solani, Spondyloeladium atro- 

 virens, Fusariuni oxysporum, Oospora scabies, and Bacillus solanaccarum. 



Blotch and streak in potatoes, A. S. Hoene {Jour. Roy. Hort. Soc. ILondon], 

 39 {1914), No. 3, pp. 607-614, pi. i).— Reviewing the previous progress of inves- 

 tigations (E. S. R., 24, p. 247) on what it is thought may prove to be two forms 

 of a single disease recently prevalent in the British Isles, the author describes 

 experiments carried out at Wisley in 1912 and 1913. 



It is stated that while in 1912 streak appeared in about 10 per cent of the 

 tubers from diseased parent tubers, in 1913 no case of streak occurred. Dis- 

 79934°— No. 3—15 4 



