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Adjuvants

Tank mixture adjuvants are usually mixtures of additives which are selected for specific functions.

 

Adjuvants are materials added to crop protection products or agrochemicals to enhance the efficacy of active ingredients and improve the overall performance of the product.

Adjuvants are usually available classified as adjuvants or activator adjuvants. Ancillary adjuvants may alter physical properties spray mixture with increasing activator adjuvants biological activity of the pesticide. In practice however, these features are often associated with each the other and not always clearly distinguishable.

Tank mix additives, mainly with herbicides, are increasingly used in World.

 

The expected benefits are dose reduction, efficacy adjustments and drift limitation. By mode of action, three main families can be distinguished: surfactants, oils and salts. Surfactants reduce the surface tension of the spray liquid and can also promote absorption of the active ingredients into the leaves. Oils above "penetrants" are mainly compatible with lipophilic active ingredients, such as specific graminicides. Salts are better hygroscopic and beneficial with hydrophilic active ingredients such as bentazone, glufosinate or glyphosate.

The expected benefits are dose reduction, efficacy adjustment and drift limitation. According to the mechanism of action, three main families can be distinguished: surfactants, oils and salts. Surfactants reduce the surface tension of the spray liquid and can also help to absolutize the active ingredients in the leaves. Oils are penetrants  generally compatible with lipophilic active ingredients such as specific graminicides. Salts are better hygroscopic and beneficial with hydrophilic active ingredients such as bentazone, glufosinate or glyphosate.

Synergism (Crop damage)

When products synergize, the application becomes too potent. For example, an adjuvant could affect crop retention or uptake, exposing it to more active ingredient or overwhelming crop metabolism. The result is damage to the crop we are trying to protect.

Antagonism (Reduced efficacy)

When products antagonize, the application becomes less potent. There are several examples:

pH adjusters in one product may reduce the half-life of another product (e.g. The fungicide Captan has a half-life of 3 hours at a pH of 7.1 and only 10 minutes at a pH of 8.2.)

Active ingredients may get tied-up on the clay-based adjuvants in other products (e.g. glyphosate tied up by Metribuzin).

One product changes the uptake/retention of another. For example, a contact herbicide burns weed foliage beyond its ability to take up a lethal dose of systemic herbicide.

 

Physical Incompatibility

Physical incompatibility affects work rate and efficacy. Products form solids that interfere with or halt spraying. It can also make sprayer clean-up more difficult. For example, weak-acid herbicides lower the pH of the spray mix, reducing the solubility of Group 2 herbicides (i.e. imidazolinones, sulfonylureas, sulfonanilides). The oily formulation then adheres to plastic and rubber surfaces in tanks, connectors and hoses.

There are many forms of physical incompatibility:

  • Liquids can curdle into pastes and gels that clog plumbing to such an extent that flushing cannot clear it and a manual tear down is required.

  • Dry formulations don’t hydrate or disperse, becoming sediment that clogs screens and nozzles. Even if they are small enough to spray, they reduce coverage uniformity. For example, a dry product added behind an oil gets coated, preventing it from hydrating.

  • Certain product combinations may cause settling, or one partner is more prone to settling. If the sprayer sits without agitation, settled products may or may not resuspend.

  • Certain product combinations may cause foaming, or one partner may be prone to foaming, causing overflows or breaking pump suction. When products foam, dry products added through the foam may swell, preventing hydration.

  • Phase separation occurs when products layer in the tank. Consider oil and water. Even with agitation, the active ingredients may not be uniformly suspended in the tank and coverage uniformity will be reduced during spraying.

Adjuvant is a product that optimizes the efficacy of another (mainly - herbicides, insecticides and fungicides), and ultimately reduces limiting factors during spraying of Crop Protection (CP) products.

Limiting factors for a successful application of CP products:

  • Climate/weather

  • Water quality

  • Specific CP management

  • Droplets

  • Sprayers

  • Etc

Adjuvants offer solutions for farmers in three beneficial areas:

1. Technical benefits

  • Limiting factors for successful treatment

  • Modern spraying:  

  1. Increasing application speed

  2. Reducing water volume

2. Economic benefits:

  • Better CP treatment balance cost/ha vs effectiveness

  • Better CP application management

  • Sufficient product effectiveness >> A.I. (active ingredient) full protection = 100% biotic action

3. Environmental benefits:

  • Better applications focused on pest/ diseases targets

  • Less CP product waste:  

  1. Reduced drifting

  2. Reduced evaporation effect

  3. Reduced soil loss 

Benefits derived from using adjuvant products are applicable in the treatment tank, during spraying, as well as directly on weeds, pests or target diseases.

In the treatment tank, these substances mainly act on two factors. These directly influence protection of the active ingredient (a.i) from chemical, fungicide, insecticide or herbicide products, such as the pH control of the treatment broth and water hardness.

The pH is intimately linked to the preservation and the phytosanitary degree of effectiveness dealing with the phytosanitary product’s active ingredients. This decreases drastically if we move away from the optimum range (5.5 – 6.5 pH). In this way, the adjuvants produce an acidifying effect, which ensures an optimum pH, guaranteeing maximum phytosanitary expression of the products.

On the other hand, they act and modify the complexation process, which immediately shows cations in hard waters (Ca 2+, Mg2+, Fe3+, etc.), produced by hard waters, blocking anions (more of phytosanitary products have negative charge) that interfere in the dissolution of chemical assets during treatment broths. Ultimately, allowing to free assets in order for it to carry out its action on the target pest and, or, disease.

During the spraying process, they give the treatment broth physicochemical characteristics. This calls for a more precise and controlled spraying. The main features are described below: 

  • Spreading, reduces the surface tension of droplets

  • Penetrating, facilitates passage of active ingredient from phytosanitary product into plant tissue

  • Retaining, prevents runoff and losses of a.i into the soil

  • Sticking, sticks contact products to the leaves

  • Moistening, captures humidity from the air and extends droplet lifespan

  • Diffusing, facilitates plant translocation

  • Drift control, improves the performance and precision of spray applications

  • Anti-leaching, protects from rainfall 

Finally, the adjuvants bear their effect directly on the targeted weed, pest or disease, enhancing phytosanitary action. Next, we highlight the effects which are the most important features: 

  • Offers retention in irregular / non uniform plant shape

  • Improves spreading on foliar surface

  • Adds penetration properties on foliar cuticle/thickness

  • Works to facilitate spreading, wettability and retention on hydrophobic leaves/plants.

  • Persistence which improves efficacy along with its target coverage over a long period of time. This limits the adverse factors (long flight distances, humidity, cuticle waxes, etc.).

  • Reduces the risk of off-target drift 

Agrosps is developing a wide range of agricultural adjuvants, with the objective of creating a relationship with the farmer while providing effective solutions that help improve product competitiveness.

Agrosps will revolutionize the Global adjuvant market!

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