There is fungus among us, and I think it's killing my plants...along one side of my front path, anyway. Unfortunately, I missed the opportunity to have David Deardorff and Kathryn Wadsworth (authors of What's Wrong With My Plant? (And How Do I Fix It?) diagnose my garden malady in their three-part guest series on Garden Rant, so I had to do it myself. Luckily, I had help from their book, which I won in a contest on May Dreams Gardens. Garden bloggers helping other garden bloggers--isn't it great? I think so!
(Warning--this a long story, so if you're stopping by for a brief visit, you might want to bookmark this post and come back later.)
The whole sordid mess begins with this pretty little autumn sage (Salvia greggii) I posted about on March 30. It's easy to see why some call it 'Cherry Sage.' I was simply delighted to see it 'spring forward' so lushly after last summer's drought and winter's 17° F freezes.
Alas, my delight was short-lived. A week later, on April 7, I noticed the entire plant was drooping, and some of the stems on the north side of the plant had turned all brown and crunchy.
Closeup of the brown crunchy bits, big noisy sigh.
Ten days later, on Saturday, April 17, the autumn sage, S. greggii, a reliable and hardy native plant for Central Texas xeriscapes, was stone-cold dead. What on earth takes out an established salvia greggii in ten days?
I knew I had a big problem, but what? I saw no insects (other than bees and butterflies), no scale, no mold, no growths, no galls, no root nodes, no oozing, nothing obvious. And nothing I read on the Internet about S. greggii gave any clues.
Wildflower.org: "[Salvia greggii] is disease and insect free and drought tolerant, and once established, should not be fertilized."
University of Florida IFAS Extension: "No pests or diseases are of major concern."
Jerry Parson's Plant Answers: "Most gardeners find Salvia to be relatively pest - and disease - free."
Two plants down from the dead salvia, a nearby white autumn sage testified to the hardiness of the species.
So who killed Cherry Sage? I didn't know, and my Twitter garden buddies didn't, either. I decided to chalk it up to a mysterious, isolated incident. I dug up the dead salvia and threw it in the trash.
The following Saturday, April 24, I noticed the blossoms of the Bath's pink dianthus that looked so healthy on April 6 and April 17 had completely flopped over. Fearing the worst, I decided to try peeking underneath the plant. To my horror, I found I could lift the entire huge mound up off the ground, except for one small section that remained fully rooted. The bottom of the plant was brown and wilted, and a horde of pillbugs were having one heckuva party under there. I also noticed that some of the wood bits within the compost under the plant had white growth on them. Ohh, that can't be good, can it?
I'm no expert, but I figure rotten roots are a sign of root rot. Ya think?
Between the Bath's pinks and the spot where the autumn sage died, I realized the Mayfield Giant coreopsis was clearly drooping. Uh oh. I'd been thinking maybe the plant was just getting too big to hold itself up (it's huge); now I'm thinking, Oh nooo, not the coreopsis too!
I peered down into the center of the giant mound, and found telltale signs of fungus. Brownish-black shriveled stems and leaves at the base. Holes in the leaves with brown edges. And pillbugs, feeding on the dead bits.
Looking closer, I noted mottling on the lower leaves. Mottled leaves are often seen with plant viruses, but according to "What's Wrong with My Plant? (And How Do I Fix It?)", similar leaf patterns may also reflect a fungal attack. Fungus can also cause plant collapse; once one has ruled out insects, nematodes, drought, salt damage, transplant shock and mechanical damage, fungi remain the primary suspects.
So far, all signs seem to point to a fungus. But what fungus (and does it matter)? I didn't think the fungus that took out my lawn 2 years ago, Take-All-Patch, could be attacking my disease-resistant native perennials. Take-All-Patch (Gaeumannomyces graminis var. graminis) is said to attack only turf grass, particularly St. Augustine. Nevertheless, if fungus killed my lawn, and if fungus is killing my garden plants, this certainly suggests that conditions are right in my front yard for fungus to flourish.
I kept reading, researching, and Googling, and eventually came across this document from Chase Horticultural Research which suggests that Rhizoctonia spp. enjoys attacking coreopsis, dianthus AND salvia. Chase Horticultural Research is a private research and diagnostic lab for the ornamental horticulture industry. Their article on Rhizoctonia states this soil-borne pathogen can cause root, stem and foliar diseases which can decimate entire beds in a few days in hot, wet conditions. Well now. It has been warming up, and we have had a lot of rain. So is this Rhizoctonia my culprit, or is it a garden-variety verticillium, fusarium or pythium? Unfortunately, it's hard to know without a $100 diagnostic culture, or at the very least, a sample of the affected plant, encased in a Ziploc bag and toted down to the local nursery for the staff to take a look-see. (Ever try to fit a 4-foot 'Mayfield Giant' coreopsis stem into a Ziploc bag?)
At times like these, when naturally hardy plants are dying, most gardeners will conclude that Something Has to Be Done, and that Something usually comes in a powder or liquid to be sprinkled or sprayed upon said plants. Because I use organic methods, I try to choose products that are effective, yet do no harm. Although the 'do no harm' part doesn't always work out, I try anyway. In this spirit, on Sunday, I treated the entire front garden with a 2 ounce, $23 packet of Actinovate. Actinovate is an organic, broad-spectrum fungicide made by Natural Industries in Houston, Texas, a hot and humid city where folks know about fungus. The ingredients in Actinovate are approved by the Organic Materials Review Institute (OMRI) and are nontoxic to insects, fish, invertebrates, pets and people. It's reportedly effective in treating a wide variety of fungi including Brown Patch, Take-All Patch, Dollar Spot, Powdery Mildew, Black Spot, Downy Mildew, Botrytis, Pythium, Alternaria, Phytophthora, Fusarium, Rhizoctonia, Verticillium and other root decay fungi--so if Rhizoctonia is taking out my plants, Actinovate should handle it, and if some other fungus is the culprit, Actinovate should handle it.
The active ingredient in Actinovate is a beneficial microorganism, Streptomyces lydicus strain WYEC 108. According to the manufacturer's literature, when Actinovate is used as a drench, S. lydicus colonizes the root system, feeding off of the plant's waste materials and preying on pathogens while secreting beneficial and protective by-products. These by-products also aid plants in complexing minerals and micronutrients found in the soil, allowing easier uptake. Actinovate can also be used as a spray to combat foliar or surface fungi.
Other eco-friendly fungicides include Serenade and Exel LG. Serenade contains a different strain of 'good bug', Bacillus subtilis (QST 713 Strain). However, Serenade is a foliar treatment which, although effective on surface fungus like powdery mildew, may be of limited use in treating soil-borne fungi like Rhizoctonia. Exel LG is a systemic broad-spectrum fungicide containing mono- and di-potassium salts of phosphorous acid, which are considered environmentally safe but are not technically organic. Like Actinovate, Exel LG can be used as a foliar spray, soil drench, or incorporated into soil; unlike Actinovate, Exel LG is not OMRI-approved and does not specifically state effectiveness against Rhizoctonia on the label.
Two years ago, I'd used Actinovate on my dying lawn, on the recommendation of Dromgoole's Natural Gardener. Perhaps the turf was too far gone, or I didn't apply enough of it, but Actinovate didn't seem to help. Nevertheless, I decided to try Actinovate again. Although it was too late for Cherry, I hoped Mayfield and Bath would see a benefit. I drenched the coreopsis, dianthus and remaining salvia with Activovate, and sprayed the rest of the garden with the leftovers.
The result? Two days later, the Bath's pinks perked up, the white autumn sage remained unscathed, and the coreopsis? Still floppy, but stable, and look, skippers don't mind a little floppiness. They're happy to feed on the blossoms, even when they're practically laying on the ground.
Words and photos © 2009-2010 Caroline Homer for "The Shovel-Ready Garden". Unauthorized reproduction is prohibited.