244 EXPERIMENT STATION RECORD. 



DISEASES OF PLANTS. 



Report on plant diseases prevalent in Nebraska during the season of 1905, 

 F. D. Heald {Nebraska Sta. Rpt. 1905, pi). 19-81). — Notes are given on the 

 occurrence of a large number of plant diseases observed in Nebraslia during 

 the period covered by tbis report, the data being arranged under different 

 groups according to the host plants. In addition suggestions are given for the 

 prevention of these diseases, so far as means are Ivuown. 



Infection experiments with Erysiphe graminis, G. M. Reed {Reprinted 

 from Trans. Wis. Acad. Sci., Arts, and Letters, 15 {1905), pt. 1, i)p. 135-162).— 

 The author reviews the im'estigations of a number of experimenters on the 

 specialization of mildews, the investigations seeming to indicate that " although 

 there are definite physiological species, normally restricted to one or a few host 

 plants, yet injured host plants of one physiological species may be infected by 

 spores of another physiological species and, in this way, the mildew may be 

 bridged over from one host plant to another." 



The author reports a considerable number of infection experiments, using the 

 conidia of E. graminis from blue grass and rye. For the most part he has 

 sought to infest grasses that are in common cultivation and which are conse- 

 quently often exposed to infection from both rye and blue grass. To test the 

 results reported by Marchal (E. S. R., 14, p. G66) spores from rye were sown on 

 wheat, oats, barley, wild barley, soft brome grass, and a number of species of 

 Poa. With one exception, none of the seedlings or leaves inoculated became 

 infected, although the experiments were continued from 8 to 15 days. A further 

 experiment showed that the spores from rye would not infect other cereals. 

 The experiments with mildew from blue grass showed that this mildew would 

 not readily infect the other species of Poa experimented with. 



In conclusion the author states that his experiments indicate that spores of 

 the mildew from one grass will not infect a grass belonging to a different genus. 

 It is quite possible that for E. graminis there is one, if not more, distinct physi- 

 ological species for each genus of grasses that contains species which are hosts 

 for this mildew. In many genera of grasses the specialization has undoubtedly 

 gone still further, so that there may be a number of physiological forms upon 

 the various species of the same genus. This is indicated by the author's work 

 vpith various Poas and leads him to the conclusion that there is more than one 

 at least partially differentiated physiological form for this genus alone. 



A brief bibliography concludes the publication. 



A preliminary report on the blast of rice, 11. Metcalf (South Carolina Sta. 

 Bid. 121, i)p. ■'jS).- — This bulletin is the result of studies and investigations on 

 rice diseases carried on in cooperation between the South Carolina Experiment 

 Station and the P>ureau of Plant Industry of this Department. The present 

 bulletin is preliminary, and further investigations are to be carried on with fer- 

 tilizers and other methods of soil treatment, as well as experiments to determine 

 the exact nature of rice blast. 



Rice blast is known to be present in practically all of the regions devoted to 

 rice culture in South Carolina and it has also been reported from Louisiana and 

 Texas. In addition to lowland rice it is known to affect upland rice wherever 

 grown in South Carolina, and while in general the disease resembles that called 

 brusone in Italy, it does not appear to be identical with it. 



The characteristic features of rice blast are distinct lesions at one or more 

 joints. Beginning as small spots on the sheath nodes the tissues underneath 

 gradually die until the joint is partially or entirely involved. In consequence 

 the parts of the itlant above the affected joint die by degrees. This cutting off 

 may take place at any joint above the water and at any stage from the shooting 



