Tall Bearded Iris diseases
What should I do if my iris gets sick?
One of the easiest ways for your iris to catch a disease is through an open wound. Therefore use clean shears to trim brown foliage away and cut rhizomes apart instead of breaking them.
Diseases to look out for:
Rhizome Rot: This occurs in the spring and in very wet climates and is the most serious iris disease. It normally starts at the bottom of the stem and travels down into the rhizome turning the plant brown, soft and foul smelling. . Use of fresh manure or excess nitrogen, coupled with poor drainage, contribute to soft rot development Cut the affected parts away and rinse with a 9 part water to 1 part bleach solution. Rhizome rot rarely kills a plant outright if the correct action is taken immediately.
Crown rot fungus: Causes a rot at the base of leaves where they join the rhizome and causes them to fall over. It is identified by reddish-brown "mustard seeds" which are produced by the fungus. Trim leaves to admit more sunlight and air movement to the rhizomes; carefully remove and destroy all diseased leaves.
Leafspot: This may be a problem during the spring and summer and especially for areas with wet weather. Small brown spots will start to show on the leaves. This is nothing to worry about but it is unsightly. Affected leaves should be cut back to help with the air circulation. The best solution is to keep the plants clear of old foliage and try not to let them get overcrowded. Since disease organisms overwinter on old foliage, cut and destroy leaves of infected plants in the fall.
Scorch: Most recognized when the leaves turn bright orange/brown beginning at the tip and look like they have been scorched. This is most likely the result of not enough moisture or starvation. Sometimes plants can be saved by replanting in fresh soil.
No Bloom: Plants that have not bloomed in the same location should be moved. Check that they are getting a minimum of 6 hours of full sun per day. Iris must have good drainage and not be planted too deep.
Plant away from large trees and or buildings. Iris need good air circulation and direct sunlight.