Hostas Under Threat?

The hosta plant, one of our favorite northern shade perennials, is coming under siege from a recently discovered virus, known in the pathologist's world as Hosta Virus X (HVX). Gardeners who have these plants need to identify the symptoms and take necessary steps to help contain or eliminate the spread of the virus. Dr. Ben Lockhart, University of Minnesota, discovered the virus in the mid-90's, and thanks to his efforts, a lot more is known that will help the home gardener.

The most commonly seen symptoms of HVX are found on the gold and yellow-colored hostas. The leaves take on a mottled appearance, especially along the veins of the leaf, often having the appearance of ink on blotting paper soaking out from the line along the vein. To some extent, the leaves become shriveled and deformed, with less vigorous growth. In some varieties, HVX shows up as spotting on the leaves. Wherever these signs are accompanied by puckering or crinkling of the leaf at those color changes, it is a virtual certainty that the plant has HVX.

As with most viral diseases, some varieties of hostas appear to be resistant while others are much more susceptible. The long-term effect of HVX is to weaken the plant, leading to its eventual death. This virus does not affect non-hosta plants.

Infected plants have found their way to all the big box stores as well as the reputable nurseries. An infected plant can live several years before the visible symptoms are seen.

All parts of a hosta infected with HVX should be regarded as carrying a highly contagious virus and handled with this in mind. Hands and any tools used on these plants should be sterilized before contacting any healthy plants (a 10% bleach solution for tools). The virus only exists in living plant material. It will not be present in the soil, so new plants may be planted where a virused plant was dug, as long as there are no living hosta roots remaining there. The virus will not spread to other plants just by growing near them.

HVX spreads from one plant to another when cell tissue of the infected plant makes contact with cell

tissue of the healthy plant. This potentially occurs when dividing infected and healthy hostas at the

same time, using the same tool. Animals such as deer can potentially spread the virus when feeding

on hostas. Trimming off damaged leaves will also move sap around, as will stepping on the plants, or injuring them in any way. Pieces of roots left behind from digging the plants may also harbor the virus.

Nurseries that have brought in any batches of hostas that include infected plants should destroy or return the entire batch as infected, not just the symptomatic plants.

Never buy a hosta that has a mottled pattern. If you see that friends have purchased a virused hosta, impress upon them the importance of getting rid of it before they start unknowingly spreading it. Alert nursery owners/managers that you MAY have observed signs of HVX in their hostas. Be careful about buying hostas by mail order - sight unseen.

Any plants showing signs of infection should be immediately disposed of, for example, dug up and taken to the landfill.

The best way to avoid getting HVX in the garden is to buy quality, disease-free plants. Leaves can be tested at the plant diagnostic clinic, University of Minnesota http://pdc.umn.edu. There is a $25 minimum charge for virus testing. Much of the information gathered from various websites.