Managing Canada Thistle in Organic

Canada thistleArvense is a type of plantThe approach to farming is different in both organic and conventional systems. The challenge is more on organic farms. It is difficult to eradicate this introduction from Eurasia, so organic growers should think in terms of management. Organic management methods are used

  1. There is still time
  2. Smother/cover crops are used
  3. Defoliation
  4. Biological control agents

Understanding the life cycle and growth of this weed helps in understanding management approaches

Canada thistle is difficult to control because of its extensive root system, which can grow up to ten feet deep and up to ten feet horizontally. Canada thistles produce allelopathic chemicals that can affect seed germination and plant growth. The growth of beneficial soil microbes such as mycorrhizal fungal species is hampered by these chemicals. ‘

Canada thistle is in competition for resources below ground and above ground. The weed is so aggressive because our annual crop systems don’t provide enough competition below or above ground

Life-cycle and reproductive issues

Canada Thistle is a perennial that can reproduce from seed, but it is a noxious weed in most states. The root segments of Canada thistle populations can be transported on equipment. Once a population is established, the field is mostly covered by roots and buds


The bud stage of plants can be reached in late May to mid June. A plant can produce 1,200 seeds or more, which can remain viable in the soil for more than 20 years. Plants within a patch are either male or female and must be pollinated by insects. Animals, clothing, farm equipment, and contaminated crop seed are some of the things that spread seeds

Vegetables have a root system

Plants from root buds are more aggressive and can compete in most systems, but it takes eight to ten weeks to establish a perennial plant system

The shoots from Canada thistle are new and viable in the spring from the buds that are new. Thousands of buds can form per square foot of soil, but only a small percentage will grow into shoots. New shoots may form from parent shoots when mowed, but the rest of the plant stays dormant due to hormonal suppression


Weed scientists note that weed management in organic farming systems requires the use of multiple physical, biological and cultural tactics. Control methods will result in the best suppression when working with Canada thistle

The stubbornness is 1

Canada thistle was controlled by tilling every three weeks

Kills emerged after Tillage broke up the root system. The deep-tillage passes break up the established roots. After buds have emerged, shallow tillage kills the new shoots. The root system is broken up by cutting it into segments, which stimulates root buds to grow and depletes the important reserves of Carbohydrates. When the shoots start to replenish the root reserves, the flow of nutrients from the roots to the shoots ceases

Some organic growers use this strategy after a small grain harvest. Jon does weekly tillage for six weeks after a small grain harvest. He chisels at 6 to 8 inches deep and then disks 3 to 4 inches deep in a week. He plows and follows with an oat-forage pea fall cover crop after this series of passes. Jon uses this strategy only once every six years and reports excellent thistle suppression, with corn yields increased 35 bu/A compared to corn following a heavy thistle invasion

In the summer, Paul uses shallow tillage every 2 to 3 weeks on his farm. He has a cover crop mix of oats, 4010 forage peas, brassica, and sunflower. He works this cover crop with vertical tillage in the spring. He works down to the height of 4 to 6 inches before planting corn to get a flush of self-seeded buckwheat

There are two things: SMOTHER/COVER CROPS

Sudangrass is a warm-season summer annual that is a great smother crop for Canada thistle. Dave Campbell has used this strategy for years after participating in an Illinois study to evaluate the smothering effects of sudangrass and sudangrass with cowpeas. The research showed that Canada thistle populations were reduced by 96%. The thistle was not adequately suppressed by summer fallow and buckwheat

Dave tills three to four times in the spring with his quack digger, then plants a hybrid in June. Dave is considering going up to 60 lbs., because he drills a heavy seeding rate of 50 lbs/A. He wants a very thick stand to shade the Canada thistle. He chops this in August and doesn’t remove the forage, then allows the sudangrass to grow as the weather allows. He chisels the field after the frost has killed the sorghum. He avoids early fall tillage to avoid stimulating new shoots from the Canada thistle plants. Dave said that the method is not as effective on heavier soils in high rain events

Paul uses a similar strategy to Dave, but instead of mowing the sudangrass he strips it just at or before he heads with his sheep flock. He has been excited about the practice of reducing his Canada thistle population2 To about 1/yd2A 98.5% reduction rate!

DEFOLIATION is a category

Canada thistle root reserves will be depleted if mowing is repeated near the soil surface. The most effective way to mow is weekly, but it results in no crop after June. A hay crop is made of hay and defoliation

Canada thistle is not as good as the other grasses, particularly the tall fescue and orchardgrass. To provide the most competition, maintain optimal fertility levels when raising hay. The thistle population will be decreased by the defoliation and the competition from established roots and regrowth. Paul Mugge is from Paullina, Iowa. Paul has a lot of his crop acres planted to alfalfa for hay. Each cycle, the Canada thistle population is placed where the seeding is moved around the farm. Paul cuts his hay four times during the growing season. Paul thinks that the Canada thistle population will be reduced by 90 percent. Paul doesn’t raise ruminants in his system so hay is sold off

The biological control agents are listed

The target species must be specifically targeted to avoid off-target impacts

Six different insect species have been evaluated for control of Canada thistle. A stem-mining weevil Hadroplontus litura is a plant The impact of the larvae on thistle stems was small in North Dakota. No other insects have been found to be effective

The disease-causing organisms can be more specific than insects. Three have been evaluated for Canada thistle control. Both The word puncitiformis is derived from the Latin word puncit A rust Psuedomonas syringae is a species ofmonas A bacteria that causes leaf spot and chlorosis was found to be in Canada thistle. Thebacteria Psuedomonas is a tribeIn a two-year experiment in Minnesota, control was promising in one year but not the second. None of these have been successful

There are methods for conventional management

Conventional growers can use a longer crop rotation or seed a hay crop as part of their management strategy. They have relied on systemic herbicides to control Canada thistle. There are different options for killing this perennial. Preemergence and incorporated herbicides are not effective. Basagran, dicamba, Beacon, 2,4-D, Liberty and Roundup are all rated as fair to good for post-emergence control. Control may need multiple applications in a growing season. Before treatment, check with your supplier and read your product label

It is important to observe and remove Canada thistle new growth to prevent it from re-establishing the root system. Control of Canada thistle requires preventing seed production and spreading. If a new patch of thistle is observed due to seed growth, control it immediately to prevent the establishment of a mature root system

We will be happy to hear your thoughts

Leave a reply

Enable registration in settings - general