630 INSECTS AFFECTING VEGETATION 



CHRYSANTHEMUMS. 



Chrysanthemum Rust. The rust is easily distinguished from 

 all other diseases that attack the chrysanthemum. It forms small 

 blisters, about the size of a pin head, or by coalescing much larger 

 ones, which appear on the under surface of the leaf, and to some ex- 

 tent on the upper surface. These soon break open and expose a dark 

 brown powder, the uredospores. On badly infested plants the leaves 

 are well covered, especially beneath, with the loose brown powder, 

 indicating the wonderful possibilities in spreading the infection to 

 healthy plants in the vicinity, as every grain of this powder is 

 capable of starting the fungus in a growing leaf, if the conditions 

 are favorable. (Ind. E. S. B. 85.) 



Having carefully reviewed the present knowledge of the char- 

 acters and habits of the fungus, only a few words will be required to 

 outline the treatment for its suppression or control. Care should 

 be taken that the rust does not invade an establishment. All pur- 

 chased cuttings or plants should be carefully looked over for the 

 rust, and also closely watched for at least a month afterward to de- 

 tect the very beginning of the disease, should it develop. If taken 

 in time, removing the diseased leaves as they appear, and burning 

 them without scattering the spore powder, is likely to stop its spread. 

 Other precautions which will occur to any cultivator, like wholly 

 destroying very badly infested plants, may also be employed. Should 

 it continue to crop out in spite of all such attention, every leaf and 

 stem above ground should be destroyed at the end of the flowering 

 period, and the young plants or cuttings for the next season's supply 

 be grown in an uncontaminated house and if possible from uncon- 

 taminated material. With an understanding of the nature of the 

 rust fungus there will probably be little difficulty in fully eradicat- 

 ing the disease by the end of the second season at the longest. 



Spraying with a suitable fungicide to keep the rust in check 

 has been recommended by a number of writers. How efficient this 

 method will prove cannot be definitely stated, as experimental re- 

 ports are lacking and the Station has not had an opportunity to 

 make tests. The Bordeaux mixture may be used, or sulfide of po- 

 tassium. For the latter, use one ounce to two gallons of water, and 

 apply weekly. No fungicide is likely to stop the disease without 

 hand picking, but if rightly used will undoubtedly prove a material 

 assistance. (Ind. E. S. B. 85.) 



Leaf-Spot. This is frequently a disfiguring disease of this 

 plant in earlier growth. It is caused by the leaf-spot fungus (Septo- 

 ria Chrysanthemi). Two other fungi, a Phyllostica and a Cylin- 

 drosporium, also attack the chrysanthemum. For indoor treatment 

 copper sulphate solution of one fourth of the strength given in the 

 spray calendar that is one pound to 50 gallons of water will prove 

 available. More applications will be required, but the foliage, will 

 not be rendered so unsightly as with Bordeaux mixture which, how- 

 ever, may be applied in full strength. 



Powdery Mildew. Powdery mildew also occurs upon chrysan- 

 themum foliage. The fungus (Erysiphe Cichoracearum) is usually 



