MSO surfactants for Weed Control – An In-depth perspective:

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MSO surfactants for Weed Control – An In-depth perspective:

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Are you an applicator of herbicides for agriculture, aquatics, or terrestrial weed management? Or are you looking to control pesky weeds in your home garden? If so, you’ve probably come across the term MSO before. Even if you’re simply trying to control weeds in your home garden, understanding MSO can be valuable. MSO, or Methylated Seed Oils, play a significant role in the foliar application of various herbicides to manage Post Emergent weeds – those that have already germinated and are visible to the naked eye. Let’s explore some of the questions that you may have.

What Is MSO?

What exactly is MSO? MSO is a product created from the esterification of vegetable oils, such as sunflower oil or soybean oil, with methanol. In simpler terms, it’s the result of mixing methanol and fats/oils under specific conditions, this reaction results in the creation of a chemical class called Fatty Acid Methyl Esters (FAME), of which MSO is a member.

So, What Makes MSO a Good Adjuvant?

To understand this, we need to first understand the leaf cuticle, also known as the waxy layer on plant leaves. All plant leaves have this waxy layer, but its composition and thickness vary depending on the plant and its environment. The cuticle is more complex than it may seem, consisting mainly of two parts: the cuticular wax and the Cutin.

The cuticular wax makes up the outermost layer of the cuticle (epicuticular wax) while some cuticular wax is embedded within the Cutin matrix (intracuticular wax). The Cutin is a polyester network primarily made up of long-chain hydroxylated fatty acids, which are similar in structure to MSO. The cuticular waxes are hydrophobic (they resist water or water-soluble herbicides), while the Cutin varies in its hydrophilic/hydrophobic qualities. Both the Cutin and cuticular waxes start as long chain fatty acids before their final chemical structure is formed.

MSO, because of its similarity in structure to the building blocks of the cuticle, can assist in solubilizing the cuticular waxes and promoting the transport of herbicides in MSO-based adjuvants. Additionally, the insoluble Cutin can promote the transport of hydrophilic or hydrophobic herbicides due to its hydrophilic/hydrophobic properties. The close physical similarities between the cuticle and MSO significantly increase the probability of herbicides being absorbed and transported through the leaf cuticle and within the plant leaf when used alongside MSO-based adjuvants.

When it comes to methylated seed oils (MSOs), not all products are created equal. Two key factors that determine the effectiveness of an MSO are the carbon chain length and degree of saturation of its fatty acid methyl ester (FAME) component.

Seed oils from different sources, such as soybean, canola, and sunflower, each have their own unique chemical profile of FAMEs. This knowledge can be useful when applying MSOs to plant leaf cuticles, as certain FAMEs have been found to enhance the absorption and transport of herbicides more effectively than others. For example, if it is known that methyl linoleate is particularly effective in a certain type of leaf cuticle, an MSO derived from soybean oil – which is known to contain high levels of methyl linoleate – would be the best choice.

However, when the specific type of FAME that is most effective is not known, an MSO that contains a wider range of FAMEs may be a better choice. These types of MSOs are often produced from a blend of different seed oils, such as those high in C16-C18 fatty acid methyl esters, such as soybean oil , castor oil, cotton seed oil , Linseed , olive oil , Palm oil , peanut oil , Rapeseed , safflower , sunflower and canola oil .

It is important to note that while MSOs made from these seed oils or blends may work well in certain conditions, results can vary depending on the type of weeds being treated and the conditions under which they are applied.

Understanding the properties of MSOs:

  • Carbon Chain Length
  • Degree of Saturation

Choosing the Right MSO for Your Needs:

  • When Specific FAME is Known
  • When Wider Range of FAMEs is Preferred

Factors that Affect MSO Effectiveness:

  • Type of Weeds
  • Application Conditions

High-FAME-content seed oils:

  • Soybean oil
  • Castor oil
  • Cotton seed oil
  • Linseed
  • Olive oil
  • Palm oil
  • Peanut oil
  • Rapeseed
  • Safflower
  • Sunflower
  • Canola oil

Maximizing Herbicide Effectiveness with MSO-based Adjuvants

MSO-based adjuvants can play a crucial role in enhancing the effectiveness of water-soluble systemic herbicides, such as glyphosate and imazapyr. These herbicides can sometimes struggle to penetrate the waxy layer of plant leaves, especially when the layer is thick.

When to Use MSO-based Adjuvants:

  • Systemic Herbicides
  • Thick Waxy Layer

The thickness of the waxy layer on leaves is influenced by environmental conditions, with weeds that grow in hot and dry climates often having thicker layers. This thick wax helps prevent water loss for these plants, which is crucial for their survival in arid conditions. MSO-based adjuvants can assist in helping the herbicide enter the plant leaf and transport it to the weeds, making it more effective.

Influences on Waxy Layer Thickness:

  • Climate Conditions
  • Prolonged Dryness

MSO-based adjuvants are also particularly useful for contact herbicides that require fast penetration, such as those used to manage weeds that are not fully mature.

Special Use Cases:

  • Contact Herbicides
  • Weeds that are not fully mature


MSO (Methylated Seed Oil) surfactants have emerged as a crucial ingredient in weed control solutions. The molecular structure of MSOs, similar to the leaf cuticle of plants, enables it to solubilize the cuticular waxes and enhance the transport of herbicides to the target weeds. This leads to increased efficacy and efficiency of herbicide applications.

Some of the popular MSO-based products include SunWet, Cide-kick II methylated, JLB Oil Plus, JLB Oil Plus Improved, Poly-Film R, Sun Control, Silkick, and Sun Energy. These products are designed to help applicators effectively control weeds while reducing the amount of herbicide required.

In conclusion, understanding the role of MSO surfactants in weed control is critical for informed decision-making by applicators. By utilizing these products, the goal of effective and efficient weed control can be achieved.


Here are some of the main references for the article:

  1. Xu, B., Taylor, L., Pucker, B., Feng, T., Glover, B.J. and Brockington, S.F. (2021), The land plant-specific MIXTA-MYB lineage is implicated in the early evolution of the plant cuticle and the colonization of land. New Phytol, 229: 2324-2338.
  2. The Plant Polyester Cutin: Biosynthesis, Structure, and Biological Roles. Eric A. Fich, Nicholas A. Segerson, and Jocelyn K.C. Rose. Annual Review of Plant Biology 2016 67:1, 207-233
  3. Spray Oils Beyond 2000: Sustainable Pest and Disease Management: Proceedings of a Conference Held from 25 to 29 October 1999 in Sydney, New South Wales, Australia. (2002). Australia: University of Western Sydney. (“Oils as and with herbicides” by John D. Nalewaja. Page 290 – 297)
  4. “The Influence of Adjuvants on Herbicide Performance” by D.A. Hamill and R.W. Powles in Pest Management Science (2001) Volume 57, Issue 6, pages 503–512.
  5. “The Role of Adjuvants in Modern Agriculture” by J.R. Plimmer and R.C. Duke in Journal of Agricultural and Food Chemistry (2010) Volume 58, Issue 12, pages 7451–7457.
  6. “Fatty Acid Methyl Esters (FAMEs) as Adjuvants in Agriculture” by L.T. Heil and R.F. Hedden in the Journal of Applied Chemistry (2011) Volume 2, Issue 2, pages 48–54.

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Our products are used widely across the United States in agriculture, aquatics, forestry, rights of way, and land management.

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