Monday, August 29, 2011

Armillaria Root Rot in the Landscape: Attack of the "Humongous Fungus"

Root rot is one of the most commonly diagnosed disease problems of woody plants in landscapes in North Carolina. Each year we see dozens of shrubs and trees that have one of the “big three” root rotting diseases: Phytophthora root rot, Thielaviopsis black root rot, or Armillaria root rot.

This article will feature Armillaria root rot. Armillaria root rot is caused by species of the fungus Armillaria. Common names for this group of fungi include the oak fungi, shoestring root rot fungi, or the honey fungi, the latter referring to the honey-colored mushrooms the fungus produces.

Armillaria is a common soil inhabitant and can infect a very wide host range including; oaks, maples, azaleas, beeches, birches, boxwoods, cedars, dogwoods, firs, poplars, rhododendrons, yews, roses, spruces, and sycamores (pretty much any woody tree or shrub). It can be destructive in orchards or on fruit trees in the landscape.

Armillaria is typically a problem in older plants or plants that have been stressed due to drought, frost, insect attack, mechanical injuries, poor drainage, low soil fertility excessive shade, or pollution damage.

Above-ground symptoms include leaf drop, dieback, and an overall decline in plant vigor. Armillaria infections start in young roots, but soon the fungus begins to decay larger woody roots.

Unlike most plant pathogenic fungi, Armillaria produces mushrooms and other structures that are visible to the naked eye. Three diagnostic signs of Armillaria root rot include:

1. Mycelial Fans: The most common diagnostic sign of this disease can be found beneath the bark (between the bark and the wood) at the base of the tree or shrub. White or creamy paper-like mycelial fans can be observed when the outer bark is carefully peeled away. These white mycelial fans can also be found beneath the bark of infected roots and root collar area.

2. Black Rhizomorphs: Sometimes rhizomorphs (dense strings of mycelium) that look like black shoestrings can be found under the bark or throughout the soil around infected tissue. Rhizomorphs serve as one of the primary means of dissemination. Rhizomorphs grow through the soil from infected trees, roots, or old stumps. They are able to directly penetrate healthy roots and cause disease.

3. Honey Mushrooms: In the fall, honey-colored mushrooms can be seen growing near the base of diseased trees and shrubs. Typically, these mushrooms grow in clusters. These mushroom produce microscopic basidiospores, but the spores are not thought to play an important role in the spread of the disease. Most species of Armillaria are edible and are quite tasty. Caution: It is always best to have any mushrooms identified by an expert before you eat them. Eating misidentified mushrooms can be fatal!


Usually homeowners do not notice Armillaria root rot until the plant is dead or dying. No control is possible at this point and the plant should be removed.

Replanting can be problematic because Armillaria can survive for many years as rhizomorphs in soil or in old wood and stumps. Remove the affected plant and thoroughly dig up and remove all large roots, stumps and any other wood or prunings from the affected area. When planting in areas where a plant has died, or where trees have been removed, as in new construction, remove all old roots, stumps, and wood before replanting. Consider planting ornamental herbaceous or perennial plants or grasses in the area for a few years before attempting to replant woody species.

Healthy trees and shrubs are better able to resist Armillaria root rot than stressed plants. Choose species that are well-adapted to your region and growing site. Maintain their health by fertilizing as recommended, watering during dry spells, and improving drainage in wet areas. When possible, prevent defoliation from insects and foliar diseases. Be careful to avoid damage to roots when digging or tilling. Do not push up soil around tree trunks and do not move soil from affected areas into sites where woody species are growing.

From: Emma Lookabaugh, Plant Disease and Insect Clinic, NCSU

Note: Special thanks to Dr. Larry Grand for helping with this article!

Monday, August 22, 2011

Pest Alert - Japanese Maple Scale

Japanese maple scale, Lopholeucaspis japonica , is active now and much of the summer. It is a small, oystershell-shaped, armored scale believed to have been introduced to the U.S. from Asia. Japanese maple scale is found in several eastern U.S. states, including North Carolina, Tennessee and Virginia. Japanese maple scale has a wide host range that in addition to maples (e.g., Japanese maples, red maples, paperbark maples, and sugar maples) Cornus, Ilex, Magnolia, Malus, Stewartia, Ulmus and others.

Although the lifecycle of this pest has not been fully examined, two generations a year are expected in the mid-southern U.S. First generation crawlers emerge in mid-May, and the second generation in early August. Management efforts are complicated by the extended crawler hatch observed for Japanese maple scales that results in first and second generational overlap. Thus, the most recent sample we received had every stage (egg to adult) present at the same time.

Adult scales and crawlers are very small and most readily observed on bark of dormant deciduous host plants, but can also be found on foliage. The waxy coating on the body of male Japanese maple scales is white and females, eggs, and crawlers are lavender. The most work on this scale has been done at the University of Maryland and their fact sheet on the Japanese maple scale is available on the web at this site.

Steve Frank, Extension Entomologist, NC State University

Thursday, August 18, 2011

Residential Rain Garden Workshop Offered August 30th

As homeowners and property managers become more aware of the issues of stormwater management many of them are choosing to manage the runoff from their homes and businesses with rain gardens. Rain gardens are shallow depressions and serve as landscape features that can effectively collect and treat stormwater and reduce localized flooding. Rain gardens can be integrated into the existing landscape as a retrofit or be included in the initial landscaping plan. To effectively manage stormwater, rain gardens must be accurately sized and properly constructed.

This 1-day workshop will present a method for sizing and designing rain gardens and detail proper construction techniques. For pre-registration call 828-697-4891 and leave your name and number. If you need more information be sure to leave your contact information or e-mail Cliff Ruth at

Tuesday, August 16, 2011

Apple Recipe Contest - September 2, 2011

The annual Apple Recipe Contest is only weeks away and NC Cooperative Extension is looking for both amateurs and professionals to enter their original non-copyrighted recipes. Winners will receive great prizes, a ribbon, and I can't forget to mention the bragging rights that accompany winning the contest at the NC Apple Festival. Recipe entry forms and the written recipe must be mailed, faxed, or delivered by August 31, 2011 to NC Cooperative Extension. If you would like more information, contact Renay at 828-697-4891.

Garden Lectures for Home Gardeners

Henderson County Extension Master Gardener Volunteers are offering a series of lectures for a small fee of $5.00 per participant for each program. Money raised is used to support future educational efforts by the Volunteers. All lectures will be held on at 3:00pm in the classroom at the Bullington Center.

Fall 2011 Schedule
Sep 19 Prepare your Lawn for Spring – Now!
Sep 26 Beauty from Bulbs
Oct 3 Success with Houseplants
Oct 17 Add WOW to your Garden with Hydrangeas
Oct 24 Putting the Garden to Bed

To register for these or other upcoming Mastering Your Garden Lectures, call the Extension office at 697-4891. Keep checking our county website for more information on upcoming lectures.

Wednesday, August 10, 2011

Bullington Center Annual Fall Plant Sale

Friday, September 9 and Saturday, September 10
10 am – 4 pm

Mums, pansies, perennials, shrubs
Visit the Garden Shed for
Gently-used tools, yard art and books

95 Upper Red Oak Trail
Hendersonville, NC

I-26 East to Hwy. 64 East, Left on Howard Gap Road
Right on Zeb Corn Road, Right on Upper Red Oak Trail

All proceeds support our gardens and educational programs
Cash and checks only

Tuesday, August 2, 2011

Announcement: WNC Naturally Events

Do you wild-harvest or grow medicinal herbs? Are you looking for a buyer? Do you make products with medicinal herbs? Are you looking for local suppliers? Are you a forest landowner looking to make some extra income from your land but don't know which plants to harvest or how to do it sustainably? Do you want to start cultivating medicinal herbs?

If you answered yes to any of these questions, register to attend one of three "WNC Naturally Events" being held in three convenient locations in western North Carolina. These are inexpensive, participatory events with sessions led by people ho have been involved in the natural products (medicinal herb) industry for many years. They are all the same, so pick the one most convenient for you. The first event is coming up real soon, so sign up now!

Here are the details:
Events: Three WNC Naturally Events
Dates: August 6, 2011, The Almond Center, Bryson City, NC
August 27, 2011, AB Tech Enka Campus, Candler, NC
October 22, 2011, Mill Spring Agricultural Center, Mill Spring, NC

For more information, or if you would like to have a table to promote your business or organization at one or more of these or would like to sponsor these
events, contact Alison at or 828-684-3562. To register on-line, please visit our EventBrite site.

This notice was provided by Jeanine Davis, Dept. of Horticultural Science, NC State University. For more information on the projects and the NC Natural Products Association, please visit this site.

Herbicide Injury on Tomatoes... A Gardeners Experiment

Jim and Elizabeth Curtis have been kind enough to share these great photographs with me. We had a few concerns that some compost they are using in their vegetable gardens might have contained herbicide residue. The first picture is of two tomato plants, one planted in regular potting soil and one planted in the compost used to amend their garden soil.

After about 2 months of the two plants receiving identical moisture and sunlight, this is how the two plants are looking. The tomato in the grey pot is the one with regular potting soil and the green pot is the one with the compost.

Here is a close up of the deformed tomato stems and leaves, common symptoms of herbicide injury.

If you need more information or help diagnosing a plant problem, be sure to contact your local Extension Office. Click here for a listing of NC County Offices.