u 



CEREAL RUSTS OF THE UjstiteD STATES. 



be equivalent to one or more of these, and it Avas for tliis reason espe- 

 cially that in the inoculation experiments with the rusts of the other 

 four cereals Indian corn Avas employed several times, as were also 

 other grasses. A few experiments were also made with the uredo of 

 maize rust itself. The following results were obtained: 



Table 12. — Inocidalion experiments with Uredo sorghi. 



Date of 

 inocu- 

 lation. 



1896. 



Sept. 17 

 Sept. 21 

 Dec. 22 



1897. • 

 Apr. 10 

 Oct. 13 



Place where experi- 

 ments were made. 



Origin of 



inoculating 



material. 



Plants inoculated. 



Manhattan, Kana j Corn Corn . . 



do 1... -do do. 



Washington, D. C- ' do do . 



do I do Euchlceiia mexicana. 



Manhattan, Kans ] Euchl cena \ Corn 



inexicaiia. i 



The time of incubation for this uredo is shorter than that of any 

 other cereal rust, varying from five to eight days, under ordinary 

 greenhouse conditions. 



Until recently it was not known that maize rustioccurred on any host 

 in this country except Indian corn. In pursuance of an idea long 

 entertained that teosinte {Euclilccna mexicana)^ on account of its close 

 relation to corn, might also be a host for the maize rust, the writer 

 planted some teosinte seed (obtained from the Division of Agrostology, 

 which kindly supplied seeds of various grasses used in the writer's 

 experiments) in tlie greenhouse in the spring of 1897, and successfully 

 inoculated the resulting jjlants, a longer- period of incubation being 

 required, however, than in the case of corn. On August 21, 1897, he 

 found both the uredo and teleuto stages on teosinte growing on the 

 grounds of the Agricultural College at Stillwater, Okla., and later suc- 

 cessfully inoculated corn with uredospores from the teosinte, vigorous 

 sori being produced. 



It is a curious fact that while inoculations with this rust resulted in 

 adding another host for it, similar experiments with the other cereal 

 rusts have shown that the number of their hosts is much smaller 

 than had been. supposed. The established hosts for this rust in the 

 United States, as determined by experiments so far made, are Zea mays 

 (cultivated varieties of the groups saccharata, dentiformis, and vulgaris) 

 and Euchla'ua mexicana. 



Occurrence and distribution. — Maize rust occurs in all parts of the 

 United States where the ordinary varieties of field corn, sugar corn, 

 and pop corn are grown, but it is rarely found in great abundance in 

 any locality. It attains its maximum abundance on ordinary field 

 crops about October 1, or about three months later than any other rust 

 of cereals. Whether the introduction of teosinte as a forage crop will 

 have any effect iii facilitating the spread of the rust remains to be seen. 



