Hello, I am Becky Carlberg, gardening enthusiast from Southeast Oklahoma. I have degrees in Biology from Eastern Oklahoma State College and Oklahoma State University. Teaching, research work, and competing in art shows then followed. I earned my ...
Hello, I am Becky Carlberg, gardening enthusiast from Southeast Oklahoma. I have degrees in Biology from Eastern Oklahoma State College and Oklahoma State University. Teaching, research work, and competing in art shows then followed. I earned my Master’s Degree in Plant Pathology from OSU and continued graduate work on a Doctorate of Botany at the University of Oklahoma.
With my family, we twice had an opportunity to live in Europe. We were in England for five years and then later in Germany for seven years. It was an excellent education for our sons. I returned to gardening, writing and art, became a Master Gardener, as well as an Oklahoma certified Master Naturalist. I am the gardener in charge of the Shawnee Japanese Peace Garden, a member of the Deep Fork Audubon Society, and now call my five acre Backyard Wildlife Habitat and Oklahoma Wildscape outside Shawnee home.
My name is Linda Workman Smith. The first step of my gardening journey began in the hills northwest of Van Buren, Arkansas, where my parents—both from farming families—raised seven children.
This is not to say that I’ve always had a love for gardening although over the years I’ve managed to keep my hands in the dirt. In 2000, my husband’s employment brought us to Shawnee where we settled on two acres west of town. Being unemployed for the first time in many years—and planning to stay that way—I started gardening on a small scale.
I have been a member of the Multi-County Master Gardener Association for several years and thoroughly enjoy being in the organization. I now have many flower beds and I’ve expanded my gardens to include lots of vegetable varieties, several fruit trees, strawberries, blackberries, raspberries and grapes. Every year I try to plant something different. I don’t grow a lot of any one thing, but a little bit of lots of things!
By Linda Workman Smith
Once again crown gall has reared its ugly head in one of my blackberry patches. Like an unwelcome guest who drops in unexpectedly, I spotted its dreadful visage a couple of weeks ago while doing spring clean-up; thus began my strategy for getting it to “move along.” I plan to use biofumigation and soil solarization.
What is Biofumigation?
Biofumigation is the suppression of soil-borne pests and pathogens by the use of plants that contain inhibitory chemicals. The plants can be harvested as rotation crops or cultivated back into the soil as green manure.
Biofumigation uses certain Brassica cultivars, which are grown, pulverized and incorporated into the soil prior to crop planting. The biofumigation process creates a powerful soil sterilizing agent, known as Isothiocyanate (TC) a natural gas released from Brassicaceous plant tissues. The ITC gas is released once the plant cells are damaged (by pulverization), and when the crop is rapidly incorporated into the soil the sterilizing Biofumigation effect takes place. By ploughing under green plant tissue, also known as green manure, a large amount of organic matter is also returned into the soil profile.
Successful Biofumigation offers the following benefits:
The Biofumigation effect is limited to only certain Brassica cultivars, so it is important to only use improved and recognized varieties to achieve the expected benefits.
What is soil solarization?
Soil solarization is an environmentally friendly method of using solar power for controlling pests such as soil borne plant pathogens including fungi, bacteria, nematodes, insect and mite pests along with weed seed and seedlings in the soil by covering soil with a sheet of transparent polyethylene, to trap solar energy. It may also describe methods of decontaminating soil using sunlight or solar power. This energy causes physical, chemical, and biological changes in the soil.
The following is information that I gathered concerning:
Crown Gall on Blackberries
Crown Gall disease is caused by a soil borne bacterium that results in plant tumors in the crown of the plant. It spreads by entering open wounds. Crown gall reduces stand productivity; once a field is infected, it could stay infected for many years. Do not take cuttings from any plant that shows evidence of crown gall, and remove infected plants. Also be careful to disinfect pruning tools after use on plants where crown gall may be present.
Agrobacterium tumefaciens is a bacterium that lives in the soil and infects plants through wounds. Common methods of entry are through injuries made by cultivation, pruning or insect feeding; also can occur through natural causes, such as wind and hail. Once the bacterium enters the plant it inserts a portion of its DNA (called T-DNA) from the tumor-inducing portion of the bacteria's chromosome, into the chromosome of a healthy plant cell. The expression of the T-DNA causes the overproduction of plant hormones that lead to undifferentiated cell growth in that region of the plant; thus forming a gall. Small galls usually develop within 2 to 4 weeks after infection when temperatures are 20 degrees C/68 degrees F, or above. The expanding tissues can sometimes disrupt the flow of nutrients and water. Bacteria are released from the gall into the soil as the gall decays. The bacteria are spread to new plants and areas through splashing rain, irrigation water, insects, tools and plant parts used for propagation. The bacteria can survive up to two years in the soil without a plant host.
Swellings or galls may form above ground on stems or branches or below ground on roots. The galls are usually rounded with a rough surface and a spongy texture and may darken and crack with age. The galls can be confused with galls made by insect or mites and also by physiological responses to wounding or grafting. However, the interior of the gall caused by an insect will have chambers or cavities where the insect developed. The interior of a gall due to crown gall will have a mass of disorganized vascular tissue. It is often necessary to isolate the bacteria through diagnostic methods in order to make a positive identification. The effect that crown gall may have on a plant ranges from little to no impact on the growth and production to declining plant vigor or even death. The disease has a greater impact on young plants and is of great concern to the nursery industry.
The most effective method to manage crown gall is through prevention and sanitation. Plant disease-free, healthy stock from reputable nurseries. Do not plant in areas where crown gall has been seen during the previous three years. Destroy infected plants immediately, and do not plant back into the same spot. Use care during propagation to avoid transmitting bacteria to healthy plants. Sterilize pruning tools frequently using a disinfectant such as 70 percent alcohol or 10 percent household bleach. Avoid mechanical wounding to young plants by cultivation, weed eating, etc.
Galltrol®, the biological control agent, has been very successful in preventing crown gall in blackberries. Galltrol® is a nonpathogenic strain of Agrobacterium that is antagonistic to the crown gall bacterium. It is very effective when used as a preventative, but it will not cure infections after they have occurred. Dip the roots of new planting stock in Galltrol® prior to planting and follow label directions closely.
Note: I’ve been unsuccessful in finding the aforementioned product—L.W.S.
Ellis, M.A., A.H. Converse, R.N. Williams and B. Williamson. 1991.
Compendium of raspberry and blackberry diseases. APS Press:
St. Paul, MN. 100 p.
Back to my tale:
Last spring and summer—in an attempt to eradicate the curse of crown gall from one of my blackberry patches—I removed a substantial number of canes. Then following instructions from information gathered on soil fumigation with mustard, I:
Combination of these two practices could, theoretically, increase the effectiveness of disease control on a given plot—at least that’s my opinion, for what it’s worth. Another benefit is killing lots of weed seeds.
Now to the current plan of attack.
Now I shall have to wait for the next steps which will be:
My hope is that the added soil and wood chips will hold in enough of the isothiocyanate (ITC)--which is a natural gas released from all brassicaceous plant tissues—to help mitigate, if not eliminate the crown gall bacterium in the soil.
Also am hoping to not kill this entire blackberry patch with my experimentation.
And what is life without hope?
As always, happy gardening,
Linda Workman Smith
Multi-County Master Gardener Association