DISEASES OF PLANTS. 155 



An anthracnose of red clover caused by Gloeosporiuin caulivorum, II. 11. 

 Fulton {Pennsylvania Sta. Rpt. 1912, p. 249). — The appearance, progress, and 

 effects of the disease are described. Its occurrence has been previously noted 

 (E. S. R., 23, p. 448). 



Moist weather conditions, combined with rapid succulent growth, favor the 

 fungus (G. caulivorum), whicli attacks most readily at points of injury on the 

 stems. The spores are not readily disseminated by wind, and the disease spreads 

 rather slowly. Development of a new crop of spores requires about a week 

 after infection. The spores retain their vitality for a number of months, and 

 the seeds may carry the infection, as may also clover trash. The fungus may 

 live over to a second season in tissues of the plant. 



Control measures include crop rotation < using clover sod for one season only 

 in the series), fall plowing of clover sod, early mowing of affected fields, and 

 use of clover seed from healthy crops, or of seed that have been cleaned of 

 trash and disinfected by soaking for 15 minutes in formalin solution, 1 oz. to 3 

 gal. of water. 



Germination of seed of clover dodders, H. R. Fulton (Pennsylvania Sta. 

 Rpt. 1912, pp. 250, 251). — This is a report of studies on the two kinds of dodder 

 common in clover fields in Pennsylvania, Cuscuta arvensis native to North 

 America, and C. epithymum introduced from Europe. 



Precautions to be taken in field practice are use of seed known to be free 

 from contamination, separate cutting of affected areas as soon as found, and 

 burning of the dried hay in place after sprinkling with oil. 



Hibernation of Phytophthora infestans in the Irish potato, I. E. INIelhus 

 {U. S. Dept. Agr., Jour. Ayr. Research, 5 {1915), No. 2, pp. 71-102, pis. 5, figs. 

 3). — As a result of experiments, the author claims that the mycelium of P. 

 infestans spreads in the tissues of the potato tuber and finally reaches the 

 sprouts. The growth of the fungus is retarded when diseased tubers are held 

 in dry soil or at temperatures below 5° C. Infected tubers rot rapidly when 

 placed in warm wet soil, and this fact is believed to explain the wide variation 

 in stand observed by earlier writers. The mycelium of P. infestans may remain 

 alive in seed tubers planted in the soil for at least 45 days, and it is considered 

 possible that under less favorable conditions for the soft rots the fungus may 

 live longer. None of the author's observations tend to show that the potato 

 fungus is latent in the stems and leaves of plants growing from diseased tubers, 

 as is sometimes claimed. 



Laboratory tests showed that the fungus infects not only the sprouts but also 

 the shoots that break through the soil, the mycelium growing fi'om the tuber 

 iuto the stem, where it travels up to the surface and forms spores. This usually 

 takes place in the small dwarfed shoots of the hill, which may become the 

 centers for serious infection. 



Conidia of P. infestans may be borne on the cut surfaces and sprouts of tubers 

 when planted imder field conditions, but as the cut surface corks over or the 

 tuber decays, the fructification of the fungus decreases. No evidence was ob- 

 tained tending to show that conidia borne in the soil are instrumental in starting 

 foliage infection. 



A list of publications pertaining to this subject is added. 



Report of potato scab experiments, 1914, H. C Lint (Nero Jersey Stas. Rpt. 

 191.'f, pp. 477-^^88, fig. 1). — A report is given of experiments carried on for the 

 control of potato scab, in which particular attention was paid to formalin for 

 treatment of seed potatoes and of sulphur as applied to the soil. The principal 

 conclusions have been given elsewhere (E. S. R., 33, p. 246). 

 18833°— No. 2—16 5 



