Irises are some of the most popular flowers in the world.
These amazing members of the Iridaceae family are categorized into six subgenera, 2 of which have rhizomes and 4 with bulbs.
Irises are not only beautiful, but they also tend to be easy to grow and suffer from relatively few problems.
However, the infamous mosaic virus is one major threat to your cherished iris plants.
What Is Iris Mosaic Virus?
Mosaic virus refers to a wide range of viral infections that result in a mottled or “mosaic” pattern on the infected plant’s foliage.
Mosaic Iris virus is primarily transmitted by:
- Mechanical (i.e., use of infected tools, hands, or contact between an infected plant and a damaged healthy plant).
There are 3 different types of iris mosaic virus which may also infect plants in other families.
Iris Fulva Mosaic Virus (IFMV)
This type of mosaic virus affects rhizomatous irises, especially the water-loving copper iris (Iris fulva) and its cultivars.
Other known species to be affected are:
- Siberian iris (Iris siberica)
- Leopard lily (Iris Domestica)
- Amaranthaceae and Chenopodiaceae families.
However, there may be more vulnerable species not yet discovered.
Its range is thus far believed to be only in the US.
Iris Mild Mosaic Virus (IMMV)
This Iris virus affects bulbous irises and members of the iris families:
The virus can be found worldwide, and it’s believed that most important iris cultivars are already infected.
Iris Severe Mosaic Virus (ISMV)
This mosaic virus not only affects bulbous irises and Iris x hollandica hybrids but also members of the Chenopodiaceae and Solanaceae families.
It’s found primarily throughout Europe, the US, and Japan.
Oddly enough, while this form of mosaic virus may be transmitted by mechanical means, grafting plants or simple contact between an infected and uninfected plant doesn’t appear to spread the disease.
Other Mosaic Virus That Affect Irises
It’s worth mentioning that several other forms of the mosaic virus can affect irises to some degree or other.
- Bean yellow mosaic virus (BYMV)
- Cucumber mosaic virus (CMV)
- Tobacco mosaic virus (TMV)
What Damage Does Mosaic Iris Virus Cause?
All forms of the mosaic virus have common traits, such as:
- Streaking of the leaves
- Possible mottling of flowers
While CMV and IFMV are known to affect primarily rhizomatous irises, IMMV and ISMV are exclusive to bulbous irises.
A single plant may contract more than one form of mosaic virus, and those with multiple infections tend to have far more severe symptoms.
Here are examples of symptoms to look out for:
- Plants with Iris fulva mosaic virus have a faint to a prominent mosaic pattern on their leaves.
- Both the leaves and seed pods tend to become malformed.
- Some necrosis may occur on the leaves.
- Unlike most forms of the mosaic virus, irises infected with IFMV appear to bear seeds that do not carry the disease.
As its name suggests, the iris mild mosaic virus has mild symptoms, including minor mottling.
Like IFMV, the seeds of infected plants do not carry the virus.
The real threat is with iris severe mosaic virus, which can cause the following conditions:
- Stunted growth
- Bud drop
- Flower breaks
- Leaf striping
Younger leaves tend to be the most affected, and no part of the plant is salvageable once infected.
Infected plants tend to die prematurely.
How To Control Iris Mosaic Virus?
Unfortunately, there’s no cure for plants infected with any form of mosaic virus.
Using chemical or organic means of pest control to keep aphids away from your irises can be the most straightforward, most effective means of prevention.
There’s also some evidence that spraying mineral oils and perimicarb insecticides can help prevent the spread of mosaic virii to some extent.
Another good way to help prevent mosaic virus spread is to keep the area around your irises free of weeds and debris.
Here are some tips to follow:
- Always sterilize your tools before and after every cut, especially when moving to another plant.
- Some good ways to sterilize are a solution of water with 15 to 20% percent bleach, intense heat, or rubbing alcohol.
- Carefully dig up and destroy any infected plant, making sure not to leave bits of infected root behind.
- You may also wish to sterilize the soil and discard any containers the infected plant was in.
While it’s possible to salvage the seeds of an infected plant in some cases, do the following:
- Sterilizer them in a 10% percent bleach soak.
- It’s best to start from scratch, especially if you don’t know which mosaic virus strain affects your plant.
- Washing your hands between plants is also essential, as the mosaic virus can be passed on if you have the juices of an infected plant on your hands, especially when it comes to the tobacco mosaic virus.
- Finally, be sure to buy only healthy rhizomes or bulbs from a reputable source and check your plants regularly for signs of disease.
Weeding out infected plants quickly reduces the risk of spreading a mosaic virus infection to your other irises.