Iris Root Rot 



Of the few diseases attacking the iris, the root rot Tpseudo- 

 monas iridis or bacillus omniTerus) is the worst. This is a soft 

 rot or decay, with a characteristic disagreeable odor. In its 

 advance stages it reduces the entire rhizome to a putrid mass, 

 entirely different from the natural decay of the older portions 

 of the rhizome, which is sometimes hastened by wet weather. 



Root rot is usually indicated first by the sudden falling of a 

 fan of leaves, which, when taken hold of, comes away easily 

 from the decaying rhizome. Heavy, wet soil, over watering, wet 

 seasons, old crowded plants, and possibly the presence of borers, 

 all tend to create conditions favorable to the development of 

 the root rot. 



Usually the rhizome can be saved if the rot is noticed in time. 

 Entirely cut out back to sound tissue, and the wound thor- 

 oughly disinfected with potassium permanaganate — one level 

 teaspoonful of the crystals to one quart of water. If the rot 

 has not made much headway, it may be cut out without taking 

 up the roots. Ordinarily, however, it is better to take them up 

 and replant. Knives and other materials used, as well as the 

 fingers, should be carefully sterilized in the permanganate solu- 

 tion after treating each root. Rhizomes which are fully exposed 

 to the sun, and have good drainage, are seldom attacked by this 

 disease ; this is one of the reasons why it is better to replant 

 before the clumps get too large. 



Iris Leaf Spot (Heterosporium gracile) 



Usually develops after the flowering season, giving the plants 

 a dingy and unnatural look, which is quite distinct from the 

 natural drying of the foliage. Tro.jana and mesepotamica vari- 

 eties are most prone to this disease. 



If the diseased leaves are cut off and burned as soon as 

 noticed, or the upper third or half of the foliage removed 

 entirely if the disease is general, this will usually control it, as 

 the new fall groAvth is likely to be normally healthy. Spraying 

 with ammoniacal copper carbonate solution ( which may be 

 purchased from mo.st seed stores) is also helpful in preventing 

 the leaf spot from spreading to uninfected plants. 



Iris Rust ^Puccinia iridis) 



This is a typical ''rust" which forms small blisters or pus- 

 tules of a dull rust color ; it appears only infrequently. Dykes, 

 the great English authority, recommends spraying with liver of 

 sulphur. 



