292 



THE GARDENERS' CHRONICLE OF AMERICA. 



SNAPDRAGON RUST. 



During the summer of 1913 the attention of the 

 floriculture department of the University of Illinois 

 was first called to a rust on antirrhinum growing in 

 the region north of Chicago, says a report on "The 

 Rust on Antirrhinum," by Chas. C. Rees, Floricultural 

 Pathologist, Argiculture Experiment Station, Univer- 

 sity of Illinois, Urbana, 111. This rust, although it was 

 thought at the time to be of little or no economic im- 

 portance, has since, by virtue of its having spread into 

 two other states, affecting seriously the snapdragon 

 crops of a considerable number of growers, come to be 

 regarded as a serious pest. 



Prior to the summer of 1913, the rust had Iseen re- 

 ported but from two western coast states, California 

 and Oregon. In 1895 it was determined as a new 

 species by Holway, an American botanist, and named 

 Puccinia antirrhini (Diet, and Holw.). 



Then in September, 1914, the writer learned that 

 the snapdragons growing on a .private estate in north- 

 ern Ohio were suffering an attack of the disease. The 

 report was substantiated by the receipt of a quantity 

 of diseased material from that locality at the station 

 only a few days ago. 



The disease is easily recognized and each grower of 

 antirrhinum owes it to himself as well as to neighbor- 

 ing growers to examine his plants and cuttings thor- 

 oughly for any traces of infection. Within ten to thir- 

 teen days after a plant has been exposed to the rust, 

 numerous grayish white areas the size of a pin's head 

 will appear on the under sides of the lower leaves. 

 From three to five days later characteristic rusty, 

 brown pustules begin to replace these spots. These 

 pustules continue to increase in number until prac- 

 tically every leaf of the plant is attacked. The stem 

 also furnishes a foothold for the disease. 



At this stage the plant begins to wilt ; its period of 

 usefulness has passed and in a short time it is dead. 



Cuttings have also proved themselves to be quite 

 susceptible to attacks of the disease. Taken at a time 

 when their vitality is at its lowest point, the cuttings 

 fallan easy prey to the rust. The disease appears on 

 the cuttings as it does on the older plants, grayish 

 white spots appearing first, followed by the rusty 

 brown pustules. However, where the cuttings are 

 taken from diseased plants in the field, the pustules 

 may show up on the upper leaves as soon as they do on 

 the lower ones. The reason for this is obvious, as the 

 disease was already established on the plants in the 

 field from which the cuttings were taken. 



Owing to the fact that experimental work on the 

 disease is just being commenced, the writer is unable 

 at this time to advance any definite methods of con- 

 trol. However, after studying this problem for the 

 last six weeks and after having observed the infection 

 in a number of localities, it would seem advisable to 

 ■observe the following precautions : 



Examine carefully the cuttings and plants growing 

 in the house. Pay particular attention to the lower 

 leaves of the older plants, as the heavy moisture on 

 these leaves makes conditions ideal for the germina- 

 tion of rust spores. Remove at once and burn all 

 plants showing the slightest signs of infection, keep- 

 ing well in mind the description of the rust as given 

 in this article. Diseased plants should be removed, 

 roots and all, and burned with great care, as the spores 

 ■will "fly" upon the slightest provocation, and in this 

 ■way neighboring plants are infected. 



As heavy moisture on the leaves makes germina- 



tion easy for all rust spores, it would seem advisable 

 to discontinue all overhead watering. Water only 

 from below, and should the soil dry out too rapidly, 

 mulch the bench well. 



Do not propagate from a plant showing the slightest 

 signs of the rust or from a plant that has in any way 

 been exposed to the disease. The selection of cuttings 

 from diseased plants has already played too active a 

 part in the spread of the infection. 



EXl'ERIKXCE WITH THE RUST. 



Referring to report on "The Rust on Antirrhinums," 

 by Chas. C. Rees, Floricultural Pathologist, University 

 of Illinois, Arthur Smith, Reading, Pa., submits the 

 following experiences : 



"In the summer of 1913 I had a number of seedlings 

 Antirrhinums growing in four-inch pots which were 

 suddenly (apparently) attacked by a disease similar to 

 that described in your article and which resulted in 

 the majority of them dying. Although tliis was an en- 

 tirely new exjjerience, I did not attach the importance 

 to it which it no doubt deserved. 



"This year the same thing has happened. Init the re- 

 sults have not been so destructive as the aflected 

 plants were removed, but not, as subsequent events 

 have shown, before other plants had been infected for, 

 since they have been benched, the rust has appeared 

 upon many of them. I am, however, sanguine enough 

 to venture to believe that I have got the disease prac- 

 tically under control by the following means : 



"All plants badly aft'ected. that is, with stems as well 

 as leaves rusted, were turned out, the remainder had 

 all diseased leaves removed and thoroughly sprayed 

 with Fungine. The result is that the progress of the 

 disease has practically been entirely stop])ed. Some 

 plants have stems eighteen inches long with all leaves 

 for six inches from the bottom destroyed, but the' 

 stems and remaining leaves are perfectly healthy, and 

 others that were attacked are sending up healthy new 

 shoots. I began spraying three weeks ago and have 

 since sprayed all antirrhinum, those which have never 

 shown any sign of rust as well as the others, twice a 

 week, at the same time refraining as much as possible 

 from overhead watering. In this latter connection, 

 however, it has appeared to me that in the case of 

 plants in pots out of doors as well as in the ground in 

 1913, the disease spread faster during hot dry weather 

 th.an it did after the moister cool weather of autumn. 

 This was especially noticeable with regard to plants 

 in the ground Avhich had had many of the lower leaves 

 killed, but which recovered themselves and flowered 

 well after rains in September. Strangely enough, this 

 year not one plant from the same batch of seedlings 

 planted in the ground has shown the slightest sign of 

 rust. 



"The result of spraying has convinced me that the 

 jjroper course to pursue for the future is to spray as a 

 jireventative before the disease appears and to keep it 

 up throughout the season." 



QUESTIONS SIMIL.XRITV OF DISEASES. 



Regarding Mr. Smith's communication, Chas. C. 

 Rees writes : "I wish to say that if the diseased speci- 

 mens of Antirrhinum which he sent to me are typical 

 of his infection, then his plants are not suffering from 

 an attack of the rust, Puccinia antirrhini. For this 

 reason, I should say that his letter to you regarding 

 control measures, etc., has no direct bearing on my 

 article, as he is referring to a dift'erent disease of the 

 Antirrhinum entirelv." 



