16 
Iris diseases and their remedies 
When it is necessary to pack Irises for a journey of any length, it will be well to remember that 
the rhizomes are apt to decay if packed loosely in moist wrappings. It is much better to wrap them 
tightly in some mossy material that is just so dry that no more moisture can be squeezed from it. 
This wrapping excludes a free circulation of air and prevents entire desiccation. As to seeds, there is 
only one caution and that is that a small canvass bag or packet, with a label attached for the stamp 
and address, is far safer than an envelope in which the seeds are often crushed by stamping in 
the post. . 
Rhizomes that arrive much parched after a long journey are perhaps best treated by being plunged 
in old cocoanut fibre in a cold frame or in some sheltered position. With such treatment, it is not 
long before the new roots begin to push out. The rhizomes should be frequently inspected, for the 
roots grow apace when once they start. When a few roots have made their appearance, it is advisable 
to place the rhizomes at once in their permanent position, so that the fibres may grow there to their 
full length and not be broken by transplantation at a later date. 
Iris diseases and their remedies. 
Pseudomonas iridis or Iris root rot. Cf. Journ. R. H. S. xxviii. p. 662 (1904). 
Of late years this disease has been very common among Pogoniris in some gardens. It is generally 
at its worst during the flowering season, when tufts of leaves will be found turning prematurely yellow 
at the tips or stems will be discovered rotten at the base. The disease is bacterial. The rhizomes 
become rapidly soft and rotten, and emit an offensive smell. 
When a plant is found attacked, it should be lifted without delay. The soft portions of the rhizome 
should be carefully cut away and burnt, and the sound remainder, including the roots and leaves, dipped 
into a bright pink solution of potassium permanganate or Condy's Fluid. 
The Iris should then be replanted, if possible in a fresh position, in soil that has received a dressing 
of superphosphate of lime or of some other acid manure. An acid medium is fatal to the bacteria, which 
thrive in lime and alkaloids. Unless the ordinary garden soil is strongly impregnated with lime, the 
amount of superphosphate used should not exceed 1 lb. to 5 square yards. 
Mystrosporium adustum Massee, Gard. Chron. 1899, 1. p. 412, and Plant Diseases, p. 325 (1903). 
This is the disease which sometimes attacks Iris reticulata, and carries off the bulbs by hundreds. 
For this reason, it is advisable to lift the bulbs of the reticulata group at least every other year. If 
the disease is present, traces of it will then be found in the shape of black patches on the outer netted 
coats of the bulbs. Any that are badly diseased should be burnt and the rest soaked for two hours in 
a solution of formalin of the strength of one part in three hundred of water. The bulbs should then 
be dried and stored in a warm dry place until they are replanted. 
Piucinia Iridis DC. (Iris Brand or Rust). *Cooke, Fungoid Pests, p. 74. PI. v. fig. 91 (1906). 
This produces crowded patches of rusty-brown pustules on the leaves, and although a slight attack 
appears to do little harm to the plants, yet it may become so severe as to destroy the leaves entirely 
and thus greatly weaken the plants. Spraying at intervals of about 3 days with a solution of 1 oz. of 
sulphide of potassium (liver of sulphur) to 2 — 3 gallons of water seems to check the spread of this 
disease. Leaves badly affected should be collected and burnt. 
Heterosporium gracile Wallr., Gard. Chron. 1894, *■ P- 718; *Cooke, Fungoid Pests, p. 75. PI. v. 
fig. 90 (1906). 
This usually appears in late summer and autumn on the leaves of Pogoniris in the form of elliptical 
pale-brown spots with a darker margin. The foliage should be sprayed with ammoniacal copper car- 
bonate solution. This is made by mixing together three ounces of sulphate of copper and three ounces 
of sodium carbonate with one quart of the strongest concentrated ammonia. When wanted for use the 
resulting blue liquid should be diluted with twenty-two gallons of water. This disease seems to break 
out much more readily among Pogoniris species when the soil is deficient in lime. 
Where any large collection of Irises is grown together, it may be found advantageous to spray the 
plants in spring and early summer at intervals of about a month with some disinfectant, such as formalin, 
potassium permanganate or the Aseptic Spray solution supplied by R. E. Evans, Horticultural Chemist, 
Stratford-on-Avon. This precaution tends to prevent outbreaks of the above-mentioned diseases. 
