19/05/2026
“What are these yellow-brown spots on my iris leaves?” 🤔
It is Iris leaf spot disease, also known as Fungal leaf spots.
Here are some facts about it:
⭐️ It is caused by a fungus.
⭐️ Iris leaf spot is the most common disease affecting iris plants.
Description:
🌿 The first evidence of the disease is the appearance of small yellow-brown spots on leaves that are surrounded by a water-soaked border. It is most conspicuous on the upper half of the leaf in the lead up/following bloom. The spots enlarge, turn brown and dry. Eventually, the leaves will die.
Cause:
🌦️ Wet, humid-like conditions make the ideal environment for fungal leaf spot. Leaf spotting is most common during wet conditions, as rain or water splashed on the leaves can spread the spores. 💦
Treatment:
🌿 Controlling this iris leaf disease involves specific cultural management practices that reduce the production and spread of spores.
🌿 Removing and destroying all diseased and dead foliage is recommended. You can remove the infected leaf portions, but you often need to remove the entire leaf. Either way, use sterile secateurs. This should significantly reduce the number of surviving spores come spring.
🌿 You can spray with a fungicide treatment, but severe infections may require at least 4-6 treatments, repeating every 7-10 days. Be mindful that fungicides easily wash off in the rain so reapplication may be required.
🌿 Plant Irises in well-draining soil where they receive full sun and have good air movement.
🌿 Leave good space between plants and remove weeds to ensure proper air circulation.
What happens if I don’t treat the leaf spot?
⚠️ While infection of iris leaf spot generally targets the leaves, it will occasionally affect the stems and buds as well. Leaf diseases weaken the plant and that can affect the next year’s flowers. In severe cases, if it is left untreated, the weakened plant may be unable to sustain itself and underground rhizomes may die.
Important tip:
👉🏻 REMEMBER if you are treating your iris with a fungicide, you need to spray when you FIRST see evidence of the disease on the foliage. If the leaf spots takes hold, a fungicide treatment will just arrest it but it will not cure the issue.
So, it is best to get your gloves on peeps and start removing the dead foliage! Give yourself a break from weeding 🤪!
💡Remember, PREVENTION is key!💡
Hope this has been helpful.
Caitie x