Bacillus subtilis is a type of bacteria that can survive in the soil for a long time. Many strains are highly effective in colonizing plant roots and fighting plant pathogens.
They can work directly against other microbes by producing a variety of antibiotics that infect fungi or bacteria. They can also act indirectly by stimulating the plant to activate its own defense mechanisms so that it can ward off attacking microbes.
This combination of activities results in a powerful bio-control agent that is commercially available to inhibit a number of pathogens in many different cultures.
Even better – in addition to its bio-control activities B. subtilis helps the plants grow more effectively.
At Gardener & # 39; s Path we explain in detail how these bacteria work and how you can use them in your garden.
Bacillus survives harsh soil conditions
Many types of bacteria die when the soil dries out and becomes unfavorable for their growth. In contrast, types of bacillus produce spores that survive long and tolerate stressful conditions.
As soon as the conditions improve, the spores germinate due to various environmental signals.
The ability of the bacteria to survive as spores makes it easier to prepare formulations for treating plants. It is much more likely that the bacteria will survive in the long term if they are in the form of spores than as free-living bacteria.
After germination, the bacteria have special sensors that guide them to plants that they can then colonize. In addition to living at the roots, some strains of B. subtilis can also live in plants and is known as Endophytes.
Colonization of the roots
The area in the soil right around the roots can be a lush place for microbes. The roots excrete sugar and other compounds that microbes feed on. In turn, these microbes help the plant by providing nutrients that would otherwise be scarce.
This area is called the rhizosphere. Kind of bacillus usually live on plant roots and promote plant growth to such an extent that they are part of a group of bacteria known to be known Rhizobacteria promoting plant growth (PGPR). These bacteria are so important that they have their own acronym!
The bacteria form what is called a Biofilm on the plant roots. This is an entire community of bacteria embedded in a matrix made up of chemicals from the bacterial cells.
The location of the bacteria in the rhizosphere gives them a competitive advantage in the defense against plant pathogens.
Manufacture of antimicrobial compounds
Strains of B. subtilis produce a variety of antibiotics and other compounds that inhibit other microbes. It has been reported that more than 24 types of different antibiotics are produced by different strains.
These bacteria produce unusual types of antibiotics known as Lipopeptides. You can recognize the term Lipo than dealing with fat. These antibiotics interact with the fungal cell membranes (consisting of lipids) and create holes in them, which kills the fungi.
There are different types of lipopeptides, one of which is an important group Iturine. You are “is considered an excellent biopesticide. ”
Iturin A.It has been found to show antifungal activity against a wide variety of fungi and to help combat multiple plant diseases.
Another group of antibiotics is that Fencyginsthat inhibit both bacteria and fungi.
These bacteria can even inhibit the germination of fungal spores!
Induction of host resistance
In addition to attacking other microbes B. subtilis can help prevent disease by activating plants to respond to pathogens.
Plants have an active immune system and often respond to microbial threats by strengthening their immune system to ward off viruses, bacteria, fungi or nematodes.
You can respond in several ways, but one general type is known as systemically acquired resistance or SAR. Systemic means that the resistance is active in the entire system.
B. subtilis It has been shown that this type of resistance is activated in many different cultures and that pathogens are inhibited in this way.
Pathogens controlled by Bacillus subtilis
These bacteria directly control soil-borne fungal pathogens such as Rhizoctonia, Phytophthora, Fusarium, and Sclerotines. The SAR they induce in the plant can control leaf pathogens such as mildew, the fungal pathogen. Botrytis, and Sclerotines and the bacterial pathogens Erwinia and Xanthomonas.
Microbial collaboration for the benefit of plants
You are probably familiar with mychorrhizas – the fungi that live on plant roots and help them absorb nutrients. B. subtilis works synergistically with a certain type of mycorrhizae – arbuscular mycorrhizal fungi (AM).
In this way, these organisms help plants to receive nutrients such as phosphorus that are often not available to plants. The soil can be full of phosphorus, but if it is not in a form that can be easily absorbed by plants, it may lack this nutrient.
That ability means that B. subtilis helps plants, even if it doesn’t help protect them from pathogens.
Individual strains have different properties
With biofungicides like B. subtiliseverything is load-dependent. Different strains form different combinations of chemicals and differ in their ability to colonize plant roots and inhibit other microbes.
So you can’t expect to add different strains and have them work in an identical way.
The formulations also affect how well the microbes survive and protect the plants after use.
It’s best to buy an established brand that consists of a strain that has been used in a variety of crops and soil types.
Serenade® is one such formulation This is offered by a number of companies, including Arbico Organics. It was originally known as strain QST 713 before it was protected with its current name.
Use of Bacillus subtilis
You can use Serenade® for plants that range from vegetable and fruit trees to roses and houseplants.
Although this microbe is not toxic to humans or animals, it is theoretically possible to develop allergies to some of the proteins if you are constantly exposed to large amounts. Therefore, you should wear a dust / mist filter respirator if you want to apply large amounts of Serenade®.
You should apply Serenade® to the leaves of your plants at the first sign of disease. Then apply it every seven days.
With many diseases, you can increase the spray frequency to three-day intervals. You should also spray more often if your plants are really damp.
You can spray in direct sunlight or at high temperatures, but do not use it if you expect watering or rain within four hours of application.
Serenade can be used with some pesticides, but you need to check in advance whether they are compatible.
And if you run a large organic farm or one that practices good IPM (Integrated Pest Management) practices, ARBICO also has a variety of Bacillus subtilis in different strains, application methods and sizes.
This soil organism controls both root and leaf pathogens
Bacillus subtilis colonizes plant roots and directly attacks soil pathogens. It also encourages plants to activate their natural resistance, which can help fight leaf pathogens.
The ability of these bacteria to form spores is a major reason for their success in the soil, as they can only become inactive in unfavorable conditions.
Different strains differ in their properties, but the strain QST 713, better known as Serenade®, is widely available commercially to fight diseases in a wide range of plants.
Have you used Serenade®? If so, let us know in the comments how it worked.