An Introduction to NCSU Plant Disease and Insect Clinic

by Andrea Laine, EMGV

You know you’re a serious gardener when you get excited about preparing a sample for the NCSU Plant Disease and Insect Clinic. I just wish I had engaged this problem-solving staff sooner and I hope you will learn from my experience.

Over the last three or four years, the mature evergreen azaleas in my landscape – of which there were many – began to succumb to a sudden dieback. Where there was once dark green glossy leaves and abundant flowering, seemingly overnight a swath of vertical branches would turn brown and die. I was alarmed, but knew not what to do. So, I did next to nothing: I trimmed out the crispy parts and hoped for the best.

I am ashamed to admit this experience was after my master gardener training. In training we certainly learned about the services provided by the Plant Disease and Insect Clinic, but either I didn’t think my plant problem was important enough to bother someone at NC State, or I was too lazy to prepare a sample. Probably a little of both.

Inspired to act

Fast forward to this summer when two things happened that inspired me to act. First, the mysterious dieback attacked a stand of azaleas that are a key structural element in the design of my landscape (see photos above). And secondly, I noticed the exact symptoms on a few azaleas in a Durham neighborhood far from my own. The problem no longer belonged just to me; I resolved to seek a diagnosis on behalf of all of us.

My first step was to collect a soil sample from the vicinity of the azalea with the most recent dieback. The results showed that the soil pH was too high – 6.2 – where azaleas prefer a number between 4.7 and 5.3. Phosphorus was high and potassium was a little low. While all that is not a great situation for these acid-loving plants, it did not explain the sudden dieback. I needed to delve deeper.

I decided to access the NCSU Plant Disease and Insect Clinic. (You’ll find a direct link to it on the right side of this blog’s homepage as well as in the list of resources below.) I dug up a smaller azalea that had browned out a year or so earlier, left a good bit of the roots and soil intact and plunked it into a double plastic bag. Back indoors, I downloaded a submission form from the Clinic’s website, filled it out to the best of my ability and brought it and the sample to the master gardener office where I enlisted the help of our County Ag Agent Dr. Ashley Troth. Ashley submitted the sample on my behalf and we included digital images of the affected plants in my landscape. The more information a client can provide, the better will be the diagnosis and recommendations.

I had decided to remove these small, scraggly azaleas from the landscape anyway. So, I used half of one as my sample to the Plant Disease and Insect Clinic. Photo by A. Laine.

A diagnosis

A week later the diagnosis was in:  Symptoms are typical of Phomopsis dieback, a fungus disease. “The disease can be very serious if the fungus moves into larger branches and the base of the plant. This dieback was found down into the base of the plant submitted,” wrote Shawn Butler, an ornamentals diagnostician. “Presence of this disease,” he continued,  “often is an indicator of stressed or injured plants. Photos show that there is probably a problem in the root zones of these plants.  No root rot pathogens were isolated from these roots.  If the plants have been water-stressed in the past, then that might be the primary problem.” 

He also sent a root sample out to check for presence of damaging nematode populations. Some parasitic nematodes were found but populations were not high enough to cause damage.

A new pledge

I will take away at least two lessons from this experience (and I hope you do, too). The first is to seek help sooner, and the second is to not ignore long-established shrubbery. (These azaleas were planted at least 20 years ago.) The plants I inherited with my landscape deserve tender-loving-care equal to that which I provide to the plants I personally select for the landscape. 

Yet another azalea is affected. Removing it would leave a hole in the bush to the right as they have grown together over the decades. Photo by A. Laine.

Resources & Further Reading

How to submit a sample to the clinic: https://projects.ncsu.edu/cals/plantpath/extension/clinic/submit-sample.html

Meet the staff
https://projects.ncsu.edu/cals/plantpath/extension/clinic/about.html

Fees for the Clinic’s diagnostic services: https://projects.ncsu.edu/cals/plantpath/extension/clinic/services.html

Azalea care – a factsheet from Clemson University
https://hgic.clemson.edu/factsheet/azalea-care/

A comment about old azaleas from Louisiana State University
https://www.lsuagcenter.com/portals/blogs/southerngarden/problems-with-old-azaleas

Durham Master Gardener Program News

Public Events
Is your community planning a feast, fair or festival? Add to the excitement by inviting the Master Gardeners to staff a table at which your guests can have their gardening questions answered. Our “Ask an Expert” program travels all over Durham County to provide this service. Call 919-560-0528 to make a request or learn more.   


Soil Sampling
Statewide, the soil sampling kits and associated paperwork are now available in Spanish and English! Locally, you may pick them up at 721 Foster Street in Durham from the Durham County Master Gardener office.

The season for free soil samples is coming to a close next month. The last day that samples will be collected at 721 Foster Street is November 25, 2019. From December 1, 2019 through March 31, 2020 residents will be responsible for delivery of their soil samples to the NC Department of Agriculture and Consumer Sciences in Raleigh and paying for their soil to be tested ($4.00 per box).  Extension will resume accepting soil samples on March 19, 2020. There is much to gain by testing your soil! Learn more.

New Partnership with HUB Farm
Durham County Master Gardeners now serve The Hub Farm, a 30-acre farm, forest, and aquatic educational center in Durham whose mission is to improve the academic achievement and well-being of students in Durham Public Schools through experiential outdoor learning. Hub Farm engages students, teachers, and the greater Durham community in environmental stewardship, health and nutrition, and career development. The farm is a program of Durham Public Schools Career-Technical Education Department and is guided by a small staff and advisory board. It is located at 117 Milton Road. Learn more about Hub Farm.

Edible Plants Sale in April
The addition of a greenhouse at Briggs Avenue Community Garden has enabled on-site seed-starting to flourish. The gardeners hope to share their bounty of seedlings of edible plants at an Earth Day event in Durham in 2020. Stay tuned for more information!

NC Extension Gardener Plant Toolbox
Though still a work in progress, the North Carolina Extension Gardener Plant Toolbox is a great resource. It contains detailed descriptions and photographs of 3,311 plants that grow in and around North Carolina. You can search for a plant by its common name or its scientific name. Use the “Find a Plant” feature to select a plant for a specific location, or  try “Identify a Plant” to determine the name of a plant based on its flower and leaf characteristics.

The primary goal of the plant database is to help consumers select plants that will bring them joy, provide a valuable function in their landscape, and thrive where planted. Users are encouraged to consider year-round functionality and potential disease and insect problems as part of their selection process. Access the database at https://plants.ces.ncsu.edu/ now and in the future. It will only get better!

— A. Laine

Getting Back to Basics

September is synonymous with school. So, this week we are getting back to basics with a post that defines foundational gardening terms. The better you understand these terms and phrases, the easier it will be to identify, select and care for plants in your landscape.

Growing season:  The period between the beginning of growth in the spring and the cessation of growth in the fall.

Hardiness zone:  Expressed as a number and letter combination from 1a to 13b, the US Department of Agriculture has assigned a zone to every geographic area of the United States based on the average annual minimum winter temperature. Tags on plants sold commercially often identify the zone(s) in which the plant will grow.   

Microclimate. Climate affected by landscape, structures, or other unique factors in a particular immediate area.

N-P-K:  Acronym for the three major plant nutrients contained in manure, compost, and fertilizers. N stands for nitrogen, P for phosphorus, and K for potassium.

Coreopsis major, blooming along roadsides now, is a native perennial hardy in zones 5a to 9b. It attracts butterflies and songbirds and is deer resistant. The flowers are large (for coreopsis) and the stems are tall. Photo by A. Laine

Annual: Plants started from seed that grow, mature, flower, produce seed, and die in the same growing season.

Biennial: Plants that take two years, or a part of two years, to complete their life cycle. By freely reseeding, a biennial plant may seem to come back year after year, but you are actually seeing new plants.

Perennial: A plant that lives more than two years and produces new foliage, flowers, and seeds each growing season. Tender perennial:  A perennial that is not tolerant of frost and cold temperatures. Applying a winter mulch can help it survive It may die off above ground and regrow from the roots.

Woody perennial: A plant that goes dormant in winter and begins growth in spring from above-ground stems. Herbaceous perennial: A plant that dies back in the winter and regrows from the crown in spring.

Exotic: A plant of foreign origin or character; not native; introduced from abroad, but not fully naturalized.  Naturalize: The process whereby plants spread and fill in naturally.

Native plant: A plant indigenous to a specific habitat or area. Nativar: A plant that is a cultivar of a native plant. Cultivar: A cultivated variety of a species. Propagation of cultivars results in little or no genetic change in the offspring, which preserves desirable characteristics.

Integrated pest management. A method of managing pests that combines cultural, biological, mechanical, and chemical controls, while taking into account the impact of control methods on the environment.

Invasive. Growing vigorously and outcompeting other plants in the same area; difficult to control.

Noxious weed. Weeds that have been declared by law to be a species having the potential to cause injury to public health, crops, livestock, land, or other property. Noxious weeds are very invasive. There are 124 plants in NC that meet the legal criteria.

When a gardening term has you stumped, refer to the glossary chapter of the Master Gardeners Handbook for a definition – there are hundreds of entries — and a small dose of continuing education.

— A. Laine

Resources & Further Reading

Glossary Chapter of Master Gardener Handbook: https://content.ces.ncsu.edu/extension-gardener-handbook/glossary

Find your plant hardiness zone:  https://planthardiness.ars.usda.gov/
USDA Plant Hardiness Zone Map, 2012. Agricultural Research Service, U.S. Department of Agriculture.

Noxious weeds in NC: https://plants.usda.gov/java/noxious?rptType=State&statefips=37

https://plants.ces.ncsu.edu/plants/coreopsis-major/

Core Aeration of Lawns

by Carl J. Boxenberger, EMGV

Core aeration is a process by which cores or plugs of soil and thatch are removed from the lawn. Core aeration is done by a machine with hollow tines.

Soils that are prone to heavy traffic are subject to compaction. Core aeration reduces soil compaction by removing plugs of soil which opens up a channel in the lawn and allows water, oxygen and nutrients to penetrate down in the soil.

Core aeration should be done when the grass is actively growing. Fall is the time to core aerate cool season lawns such as tall fescue. Spring and early summer is the time to core aerate warm season grasses such as Bermudagrass.

Gardener operating soil aeration machine on grass lawn. Stock Photo c Mikhail Pavlenko

Core aeration equipment with hollow tines can be rented at local equipment rental companies.  There are also professional turf maintenance companies that will aerate your lawn if you do not want to tackle this by yourself.

Run the aeration equipment over your lawn to remove soil cores. Chop up the cores by running a lawn mower over them. If you have a large lawn and a tractor, you can distribute the cores by dragging a piece of chain link fence or mat over them.

Core aerate a few days after a rain. This will have allowed the soil to drain. If you pull plugs when the soil is wet they will form wet clods of soil alongside the aeration holes and actually inhibit air infiltration into the soil, defeating the purpose of aeration.

Further Reading

NC State Extension Turf Files: https://www.turffiles.ncsu.edu/

News alert about zoysiagrass mite damage
https://ncturfbugs.wordpress.ncsu.edu/2019/05/23/zoysiagrass-mite-alert/

To Do in October

by Gary Crispell, EMGV

Well, wasn’t September fun?! Dry, wet, dry, OMG wet. Heartfelt sympathies to those who suffered loss by Florence. For those of us whose gardens were only moderately affected (or not at all) here is the October calendar.

Fertilizing
Not much to do here unless you are planting spring flowering bulbs. Should that be the case, incorporate a little balanced fertilizer (10-10-10 or equivalent) into the soil as you plant. Store any leftover fertilizer in a dry place for the winter.

Planting

  • The above-mentioned spring flowering bulbs (e.g. hyacinths, tulips, daffodils, crocuses, etc.).
  • Pansies! Those plucky members of the Viola genus who can brighten up a gray winter day should be on everyone’s list unless, of course, there are deer nearby.  Apparently, the pansies make a great dessert after a meal of azalea branches.  Plant them soon as the more established they are when it gets cold the better able they will be to withstand the cold.
  • “Fall is for planting.” It’s not just a slogan from the nursery industry. It is gospel. The very best time to plant any new landscape plants you have been planning is now.
  • Peonies can be planted or transplanted now.
  • In the vegetable garden consider a nitrogen fixing cover crop like red clover, hairy vetch or winter rye. This will help keep down the weeds and add nitrogen to the soil. In the spring just till it into the soil to add nutrients and organic matter.
  • If you happen to be one of the foresighted people who have a cold frame now is the appropriate time to plant a winter’s worth of salad. Lettuce, green onions, radishes, carrots, spinach and other leafy greens will grace your salad bowl all winter if planted now.

Pruning
Once frost (It’s October. It is going to frost!) has finished the decimation of the perennial garden cut off all the dead tops and throw them on the compost pile. Root prune any trees or plants you plan to move in the spring.

Spraying
Unless you have a lace bug problem, it is time to clean up and winterize the sprayer and store the pesticides in a secured, dry location that will not freeze. As for the lace bugs, they are active whenever the leaf surface temperature is warm enough (i.e. whenever the sun shines on the leaves). A horticultural oil spray can be helpful in controlling both feeding adults and egg stages.

Lawn Care
Maintain adequate moisture levels for any newly seeded or sodded lawns.  Avoid leaf buildup on lawns.

Tall fescue and bluegrass (not the fiddlin’ kind) can still be planted in October.

Propagation
Keep an eye on any new cuttings in the cold frame (the one without the salad greens in it). They should be checked at least twice a month and watered as needed.
If you are a gardener lucky enough to be able to grow rhubarb now is the time to dig and divide it.

Other stuff to do that will keep you outdoors while the leaves turn color:

  • Take soil samples while they are still FREE. NC Department of Agriculture will charge for them from November to April.
  • Put those raked 0r blown leaves into the compost bin or till them into the veggie garden.
  • Clean fill and put out the bird feeders.
  • Dig and store (cool, dark, dry) tender summer flowering bulbs (E.g. gladioli, dahlia, caladium) before frost.
  • Clean up lubricate and otherwise prepare lawn and garden equipment for its long winter’s rest.

A mea culpa. This writer neglected to inform you that it is time to band trees that are susceptible to canker worm invasions. This involves wrapping and securing the trunk with a coarse material like burlap or quilt batting about 4 or 5 feet above the ground. That in turn is wrapped with a corrugated paper wrap that is then covered with the stickiest gooeyest stuff you’ve ever played with. All these materials are available at some nursery/garden centers, one of which is very proximal to the Durham Cooperative Extension office.

For a fun activity now that will yield fresh living flowers in the bleak mid-winter try your hand at forcing spring flowering bulbs. Plant bulbs in pots early in October and place them in the refrigerator. In twelve weeks bring them out into the house and watch them grow and bloom. Kids love it.