Even the toughest plants are susceptible to fungus

Published 6:54 pm Saturday, June 3, 2017

I thought it impossible for monkey grass to die of natural causes.

Well, I’ve always known there has to be a fungus or bug out there somewhere awaiting the right time to invade even the toughest of plants.

But liriope, aka “monkey grass” is just one of those plant species we expect to be pest-free for a lifetime, our lifetime.

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Unfortunately, there are two fungal diseases that can get severe in liriope. And just my luck, it’s apparently the worse of the two has jumped all over the liriope that I use for flowerbed borders and ground covers.

Crown rot disease of liriope is caused by the fungus Phytophthora palmivora. That Phytophthora genus is the parent of a bunch of species of fungi that cause diseases in many of our favorite plants.

Those fungi species are especially bad at and below ground level, including diseases of lawn turf, oak trees, vegetables, fruit trees and many landscape plants.  It is said in this climate even the healthiest of peach trees will be short-lived and die of Phytophthora root rot.

In Southern U.S. liriope, the fungus spreads rapidly in late spring during periods of high rainfall.

Sound familiar?

The first noticeable symptom is yellowing of leaves. They turn yellow because fungi has attacked the crown, which is the just-below-ground stem part where the leaves join. The leaves brown out fairly quickly and the plant “melts down” to the ground in a few weeks.

The other liriope disease shows up in late summer and fall, making it easy for us amateurs to distinguish which of the two we have.

The second one, called “liriope anthracnose” or “liriope leafspot” is brought on by differing species of the Colletotrichum genus. This disease first shows up as brown or red spots on the leaf edges or down the leaf midrib.

Eventually the spots grow together, causing a brown, dead leaf.

And since a dead leaf makes no plant food, the entire plant weakens when several of its leaves die out. Leafspot disease is not usually deadly to Liriope plants like crown rot.

With both liriope diseases, we homeowners/gardeners have very few control options.

Avoid overhead sprinkler irrigation; that’s the same as more rainfall on leaves.

There really is nothing practical to do to cure crown rot. “The literature” says to plant only healthy, disease-free plants. Yeah, well, I did that twenty-something years ago.

The fungi has found us. Fungicides registered for this disease are drenches pretty much relegated to the commercial nursery industry with the goal of producing healthy plants to sell.

For crown rot infections, dig up sick plants regularly and get rid of them. Likewise, pull off anthracnose-spotted leaves as they occur. Logically, the compost pile is absolutely no place to discard diseased plants and leaves.

If you cut down or mow down liriope in the late winter, rake the leaves and, Yep —  far away with them.  If you don’t normally cut back liriope in winter, do so this coming winter if your’s is sickly.
Terry Rector is spokesman for the Warren County Soil and Water Conservation District.