li'-^»] DISEASES OF PLANTS. 545 



rroduction of coiiidia iu Gibbt'rrlla sauhiiictii, J. G. Dickson and II. 

 JoMANN (.Jour. Afir. Research [('. ,s'.], J!) {liKUl), Xo. 5, pp. 23.5-2.i7, fig. 1).— 

 Kesiilts :uv j.ivt'ii of ii cooperative invest ifj:at ion of tlie Wisconsin I'Jx[)erinient 

 Station and tlie Bureau of IMant Industry, l". S. Deparlnient of A^'ric'ulture, on 

 the development of the seal) fun;;us {(1. sitiihiiictH) which attacks wheat, corn, 

 rye, barley, and oats. 



It was found that repeated crops of conidia of G. saubinetii can be produced 

 in abundance in short periods of time from ascospores, sporodochial conidia, 

 vej,'etative c-onidia, or mycelium wlien favorable moisture and temperature condi- 

 tions obtain. This ability of the wheat scab organism to produce virulent spores 

 in abundance in short periods of time is considered to have an important bear- 

 in;;' upon the development of wheat scab epidemics. 



IMiilipitine downy mildew of maize, W. H. Wkston, .tu. {.four. A(/r. lie- 

 .scarrh [U. S.], 19 (1H20), A'o. 3, pp. <n-J22, pis. 12, fifjs. 3).— The author has 

 investigated for the Bureau of IMant Industry, U. S. Department of Agriculture, 

 the downy mildew of maize, wliich has been known to occur in the IMiilippine 

 Islands for a number of years. The present paper gives results of his study 

 on tlie distribution, severity, and characteristics of the disease, and the nature 

 and relationships of the causal fungus. 



The disease is said to be extremely destructive, and representntive varieties 

 of all kinds of maize were found highly susceptible. Teosinte and maize-teo- 

 siiite iiybrids and sorghums were attacked, but with less virulence. The symp- 

 toms of the disease may appear from the time plants are seedlings with only 

 three or fou^ leaves to the time when the tassels and silk are fully developed. 

 In general, infected plants showed a yellowing of the leaves in more or less 

 restricted striped areas, a whitish down due to the abundance of conidiophores, 

 principally on the leaves, abnormal growth of vegetative parts, and abortive 

 dcveloitment of the ears, resulting in partial or complete sterility. 



The causal fungus is said to be Sclcrospora phUlppincnsis, which is described 

 as a new species, and its relationship with other species I'nown to attack maize 

 is i)i)inted out. The fungus produces conidiophores in great abundance, but only 

 at night wlu n a thin layer of dew or raia is on the leaf surface. No oospores 

 or other resting bodies have yet been found to be produced by this species. The 

 iiuthor reports having found the oospore stage of a Sclerospora on Sacchm-nm 

 .tpontancum, a common wild grass in the Philippines, but whether this is con- 

 nected with the conidial stage on maize is yet to be determined. 



Halo bliglit of oats, C. Elliott (Jour. Ayr. Research [U. S.], 19 {1920), No. 

 If. pp. 139-112, pis. 11, fin. 1). — A description and discussion of a bacterial dis- 

 ease of oats which has been the subject of investigation by the author are given 

 in a contribution from the Bureau of Plant Industry, U. S. Department of Agri- 

 culture. 



This disease was unusually severe in its attack on oats in Wisconsin during 

 ini8, and reports of a similar di.sease were received from southern Minriesota, 

 Iowa, northern Illinois, and Indiana. The disease is characterized l)y haJo- 

 like margins of chlorotic tissue about a center of dead tissue. Isolations made 

 from these lesions have constantly given a typical white organism, which has 

 been studied and the disease produced by artilicial infections. The organism 

 is believed to live over the winter on the .seed, producing primary lesions on the 

 first leaves of seedlings, and from these the organism is carried to other leaves 

 by winds and rain. In natural infections, halo blight has been observed only 

 on oats and rye, but artificial inoculations showed that the organism may be 

 slightly pathogenic on wheat, rye, and barley. The halo blight is considered due 

 to Bacterium coronafackns u. sp., a technical description of which is given. 



