The hosta has a well-deserved reputation for being a low-maintenance plant resistant to many pathogens. However, hostas are in danger from a hosta virus X (HVX).
The disease caused by the hosta virus is tricky because it can stay dormant for a long time.
You can buy an infected plant that seems healthy, plant it in your garden, and enjoy its good looks for a few years. Then, all of a sudden, the hosta will start to die.
What Causes Hosta Virus?
Dr. Ben Lockhart, a phytopathologist at the University of Minnesota in the United States, published the first scientific studies on the Hosta virus in 1996.
As a result, the X virus was named Hosta (HVX). Dr. Lockhart discovered that this virus only infects hostas and spreads through the sap of plants during bush division, leaf, and inflorescence pruning, but not through insects, fungi, seeds, or pollen.
However, when infected plants are propagated through division or tissue culture, the resulting offspring are also afflicted with the disease.
There is no cure for virus-infected plants; they must be destroyed. But the virus can’t live in dead tissue, so after two to three weeks, the plants taken out can be replaced with new ones.
In addition, Lockhart said that some types of hosta are resistant to the virus. For instance, many hybrids of Hosta Sieboldiana elegans are resistant to or even immune to the HVX virus.
Symptoms of Hosta X Virus
The symptoms of the Hosta X virus can take many forms. Intervein chlorosis and leaf deformation are common symptoms.
Spots (mosaics or speckles) may also appear on the leaves. Flowers on the infected plant either lose their original coloration or fail to open. The plant dies over time.
It can be challenging to tell the difference between a host infected with a virus and one that has been damaged by sun exposure, frost, fungi, or nematodes just by looking at it.
For example, infected plants exhibit the following color changes:
- A virus infecting a leaf will cause it to develop a pattern that looks like a fountain pen mark on blotting paper. Note that this vein discoloration is not caused by a virus and should not be confused with the naturally occurring variation in some plant species (such as the Maya Tritone).
- Deformed leaf tissue looks sloppy and unattractive, and some parts of the leaf are “chewed” and dry, with a different color and are usually denser than healthy tissue;
- It has a mottled appearance, fuzzy spots, or mosaicism.
Changes like these don’t always mean you have an HVX. Other pathogens could cause them, but either way, this is a sign of the disease, so you should get rid of it.
Some cultivars, like Kiwi Forest Hosta, have a speckled appearance that isn’t a disease symptom but rather the result of inherent genetic traits.
Lockhart tested 57 hosta plant varieties and species to write an article about which ones were resistant to the disease and which were severely impacted by it.
However, recent studies have revealed that no hosta cultivars are more (or less) resistant to HVX. Any hosta growing and exposed to HVX is likely to get infected. (Source)
There is no danger of the virus spreading to other hostas, and the plant is not at risk of dying. However, it spreads rapidly through contaminated garden tools, gloves, or other work clothes from a sick plant.
Is There Any Way To Cure The Hosta X Virus?
Unfortunately, this viral disease is incurable. There’s nothing left to do but uproot the plant and move it far away from the plot.
It’s a shame, but it’s the only way to prevent the rest of the hostas from getting sick.
If you discover this invasive disease, you should eliminate your hosta and immediately disinfect any gardening equipment you’ve used, such as a shovel, pruners, a hoe, etc.
The virus can easily be spread on a shovel when a sick hosta is dug up or when old plant parts are cut off with secateurs or scissors.
To avoid spreading the disease, it is recommended that you use disposable work gloves when removing the plant.
Use dishwashing soap to clean your tools and an alcohol wipe to clean the blades.
It’s not enough to dip cutting tools in disinfecting solutions. Pruning shears, scissors, knives, and other tools must be wiped down to remove sap residue.
Scientists used to think that the virus doesn’t stay in the soil and that a new, healthy hosta could be planted in the same spot after 4-6 weeks.
However, after doing more research on the virus, they now say that you shouldn’t plant new plants where the sick hosta was growing.
It has been found that X virus-infected plant parts and roots can stay in the soil for at least two years. (Source)
Here Are My Recommendations
When dividing hostas or trimming their roots and stems, always remember to disinfect your gardening tools:
- In high heat by burning over a fire or in boiling water;
- Use either 10% bleach or 3% formaldehyde (Formalin);
- Be wary of purchasing unnamed plants, and exercise extra caution when shopping for new varieties of hostas with variegated or dotted leaves;
- The roots and root neck should not be cut when transplanting. When dividing and caring for hostas, don’t get sap from one plant on another when you remove leaves and peduncles. Clean your tools before moving on to the next plant.
- Keep all gardening tools, pots, and gloves clean after working with hostas;
- Keep a few test kits on hand to check on new purchases. You can get HVX Immuno Strip kits from Agdia Inc.
How Do You Test For Hosta Virus?
Laboratory testing in scientific institutions is out of reach for the average host collector because it costs so much.
However, the HVX ImmunoStrip is a test kit for collectors and growers that can check hostas for the virus.
It was developed in 2008 by Agdia Inc., an agricultural diagnostic laboratory in Elkhart, Indiana, began producing the antibodies required for enzyme-linked immunosorbent assays (ELISA) that same year.
The use of this kit is quick and easy. It is a one-time-use kit with a test strip and a plastic bag with the test liquid.
- Collect some plant tissue, like a small piece of leaf or root (about the size of your thumb).
- Put it in a bag, crush it, and mix it with the formula.
- Wait for the liquid to absorb the antibody line on the test strip. If HVX is there, it will bind to the antibodies, and a positive result will appear as a red line on the test strip.
Above the antibody line is a control line that turns red whether the sample is infected or not.
So, if the test is positive, there should be two red lines; if it is negative, there should be only one. Agdia says this testing method gives 99% of the same results as serious lab tests.
However, experts from Agdia warn against making the most common mistake when testing, which is putting the strip too far into the bag of liquid.
There is a risk that this will produce inaccurate results. Using too large of a sample can also lead to erroneous results.