Pests and Diseases

The good news here is that most of the damage you see on your leaves is not going to kill your plant.  Generally, leaf damage is unfortunate, but not lethal.  If you plants have burnt edges or spots, holes or tears, or other physical damage, the plant will usually survive just fine. Obviously you want to find out what is doing the damage so you can eliminate the cause, but as long as you don't let it go to extremes, it generally won't do any lasting harm.

However, although hostas are considered rugged, easy to grow plants, they are not immortal. You need to learn the difference between leaves that have physical damage and those that show symptoms of something more serious.  If your plant has leaves that are yellowing, wilting, or simply falling off, you may actually have a problem. 

Like all plants and animals, hostas have enemies. Although they are among the the most trouble free plants you can grow, they are not immune to diseases and predators.  If you think there is something seriously wrong with your plant, it's generally surprisingly easy to figure out what the problems is.

Let's start with the two worst things that can happen to a hosta, crown rot and voles.  If your plant dies, or is on death's door, these are the two most likely causes.  You may have to dig the plant up to determine which one is causing the damage, but if you have any chance of saving the plant, you need to act quickly. 

Crown Rot

There are several diseases that are referred to as crown rot, the most common, and the one we are referring to is bacterial soft rot, which occurs most often in early spring.  It is caused primarily by freezing weather in the spring, mostly in plants that are too wet or in plants that have broken dormancy and freeze after they leaf out.

If your plants have significant leaf damage from a late freeze, be sure to check the crown to make sure there are no soft areas.  At the very least, use your finger to check under the soil surface at the base of the leaf stalks and see if you can feel any soft spots.  You may have to dig the plant to examine it. A healthy rhizome should be hard, like a potato, and if you feel anything that is soft and mushy, you have a problem.

There is a terrific web page that gives more information on hostas pests and diseases than anything I could ever write.  If you would like more information about identifying and treating problems,  About the only major pests not addressed are voles and deer, which I cover a bit below.  The link is: http://www.extension.iastate.edu/Publications/SUL14.pdf

Voles

Voles are probably the most destructive of the pests that affect hostas. The piece of rhizome in the picture is about 4 inches long.  It's all that's left of a 5 or 6 year old plant of 'Halcyon' that used to have a spread of 3-4 feet. You can see from the freshly eaten areas that the little varmints weren't finished.  If I hadn't dug up the rhizome, they would have eaten it all. Actually, this plant will regrow if we replant it.  It will be years before it's as big as it was, but it's not dead. 

Voles are small, mouse-like rodents that burrow underground. They look just like mice, except that their tails are very short. They feed on the underground rhizomes and can destroy a clump in a very short time. If your plant looks healthy one day and the next day the leaves are on the ground and no longer attached to anything, you've got voles. Sometimes the voles will use mole runs, but moles do not eat hostas.

Sometimes they will leave some rhizome and roots intact, and the plant can recover if you can protect it from further damage.  Other times, especially with small, young plants, you may find the leaves collapsed on the ground and nothing left below. If you suspect voles are damaging your plants, you can usually check simply by poking around the plant with your finger.  If you still have leaves attached and standing, you can probably find a soft spot in the soil surrounding the rhizome, the tunnel that  the vole used to get to the plant.  Or you may find that the rhizome is gone.  If you poke around and there's nothing left, the vole has finished and moved on, probably to another plant.

There are many ways to try to control voles, and your best course of action depends on a number of factors.  Cats, traps and poisons are the simplest, but with the latter two you need to make sure you're not killing anything you don't mean to.  If you have a problem with voles, I suggest you Google "vole control" and get an idea of what is possible and practical for your garden.

Deer

We seem to get more emails every year from people wanting to know what ate their hosta flowers or leaves and what to do about it.  Of course, since I wasn't there, I can't tell them for certain, but the best guess is deer.  Deer sometimes eat just the flower buds, but will usually eat the leaves too.  Sometimes they will just sample what you have and move on, other times they can destroy a planting overnight.  There are three primary ways to deter them, dogs, sprays and deer fence. 

Dogs are pretty effective, but not if they're sleeping next to your bed.  They have to be free to run the deer off from dusk to dawn to be of any use.  This is not practical in some areas.

The most common solution is repellent sprays.  There are any number of brands and I can't say which is the most effective because I don't have any experience with them. I've heard good things about Liquid Fence and Bobex, but I understand that eventually all of them lose their effectiveness, so the best thing to do is probably to alternate the kinds of sprays you use.  Check with your local garden center or farm store for recommendations in your area.

Deer fence is probably practical only as a last resort, since it requires that you fence your whole garden.  If this is a solution you want to consider, I would suggest you Goggle "deer fence" or "deer control" for suggestions.