What you need to know about the application of phytosanitary products and drift

Presented by:  Agr. Eng.Jorgelina Lezaun 
Agribusiness & Marketing Consultant
jorgelina.lezaun@gmail.com 

November 2024

It is defined as APPLICATION the use of all the scientific knowledge necessary for a particular crop protection product to reach the target, in sufficient quantity to fulfill its purpose without causing contamination or DRIFT. (Etiennot, 2005, cited in Massaro, 2005).

Pesticide application technology offers alternatives for efficient pest control, minimizing the effects of product losses and avoiding damage that may affect human health, flora-fauna and the environment, as well as the risk of causing direct damage such as phytotoxicity to crops.

The risk will depend on the degree of toxicity of the formulated products - detailed on the label - and the exposure to the product. In addition, climatic conditions, the condition of the application equipment, as well as its regulation - calibration, the technology used and the possible degree of exposure must be assessed. According to scientific studies (Maluf, 2015) more than 70% of the result of a product depends on the efficiency of the application.

What is drift?

DRIFT is the “displacement of a pesticide away from a given target, transported by air masses or by diffusion” ASABE S-327.1 Standard of the American Society for Agricultural Engineers Standard.

At an environmental level, drift control is the biggest challenge for applicators (Gil & Sinfort -2005).

Losses due to this “displacement” or drift can occur as:

1. Exo-drift or outside the field where it is applied - external to the field. The product drops are transported by wind drag and due to convective currents. It is a very dangerous phenomenon when applying agrochemicals, conditioned by both the speed and direction of the wind.

1. Endo-drift occurs when the fraction of the agrochemical is lost within the field, treatment lot/crop due to the drag, coalescence and runoff effect of the drops..

Exo-drift often occurs and the type of product applied does not allow its undesired effect to be seen (insecticides, fungicides); however, herbicides are the most easily associated with exo-drift (Massaro, 2013).

The determining factors of drift can be grouped into:

1. Intrinsic properties of the active ingredient: products with high volatile vapor pressure or biological action in the gaseous phase are uncontrollable in the field.
2. Meteorological conditions: wind speed, temperature, relative humidity, thermal differential Δ T, cause evaporation of water from the pesticide droplets. It is called thermo-drift when evaporation of small droplets occurs due to high ambient temperature and low relative humidity. The vapor pressure of the phytosanitary product formulation also influences thermo-drift.

Spray technology: spray nozzle type, individual flow rate and working pressure, which determine the droplet size. Also, the equipment's working speed and the height of the boom above the target surface.

Efficient application of phytosanitary products

When applying pesticides, it is necessary to take extreme care to ensure responsible management, in order to ensure that spraying is uniform and precise, obtaining the best control. That is, to ensure that each drop sprayed is applied to the desired target, reducing losses and risks caused by drift.

There are technical variables and environmental conditions to be analyzed and considered important due to their impact on the efficient application of pesticides.

1. Size of the droplets
   

   produced by spraying from a hydraulic nozzle or tip, expressed in microns: 1 µm = 0.001 mm. It is related to drift.
   The American Society of Agricultural Engineers (ASAE) publishes voluntary standards for the safety of the use of pesticides and agricultural equipment.
   ASAE Standard S-572.1 correlates droplet size by type, nozzle number and working pressure with the risk of spray drift. It is used globally and published by companies supplying spray tips or nozzles.

VMD Median Volumetric Diameter is the droplet size diameter that divides the mass of sprayed drops into two volumes. The DVM 0.5 divides that volume into two equal parts of 50%.

Example: VF on a nozzle that has a VMD 0.5 < 100 µm, most of the droplets are < 100 µm, and the risk of losing them during work is VERY HIGH, causing DRIFT, damage and/or contamination. 

Considering this information and its importance with the risks of loss of products and effects on “non-target” organisms, restrictions are justified for spraying with Very Fine, Fine and even medium drops, in more critical plant production areas -with use of pesticides-, that is, “peri-urban areas”.

2. Hydraulic nozzle type

3. The design of hydraulic nozzles or tips has evolved with an increasing tendency to reduce drift. Low-drift nozzles have homogeneity in droplet size and this benefit depends on the size of the drops produced by the nozzle.

   There are phases in the formation and deposition of the drops produced in a standard flat fan or low drift nozzle until reaching the target.

Slide

1. 1. Hydraulic pressure ejection:

1. Pressure
2. Mass

1. 2. Kinetic energy greater than friction
2. 3. Kinetic energy less than or equal to friction, turbulence phase.
3. 4. Laying on the surface.

1. Ausencia de polvo (permiten formulación líquida de productos que solo se formulaban en polvos)
2. Facilidad en transporte y almacenamiento
3. Medir por volumen y no pesar
4. Aplicación homogénea y fácil
5. Distribución uniforme
6. Optimiza la bioeficacia del i.a
7. Mayor residualidad y menor olor que CE

3. Spray Type

When broadcast spraying, the equipment wets the entire surface of its working width above the crops and the pesticides are directed at the entire canopy.

Directed applications are applied to the inter-row of the crop below the cultivated plants with selective herbicides. It offers some advantages, although it requires certain conditions.

Advantages of directed application:

Weather conditions for spraying

Meteorological variables such as wind, temperature and relative humidity of the air affect the spraying process, causing the pesticide to evaporate. They also do so by causing the droplets to be carried by convective currents (the “vertical” movement of the air) or by wind (the “horizontal” movement of the air).

The size of the droplets can prevent or reduce evaporation. Also, the incorporation of an additive or adjuvant that acts as an anti-evaporation agent.

“Psychrometric tables” summarize the evaporative effect of air according to its temperature and relative humidity and are a tool to help define favorable conditions for application. The spraying of pesticides in the agricultural sector is regulated according to the risk of possible damage to human settlements and/or natural water sources (rivers and streams). 

Good Application Practices to reduce drift

Due to the development of urban centers on agricultural areas, it is necessary to optimize the management and application of pesticides, as well as evaluate alternatives that contribute to good practices in their application.

With the technology available today, it is possible to control and reduce drift; and satellite agriculture and ongoing training tools are useful to assist farmers and operators in decision-making.

To achieve the objective of reducing drift, it is necessary to take into account:

1. Technical aspects

1. Application techniques and equipment It is important that the calibration of the machine is carried out by a trained operator who is familiar with the machine and knows how to adjust it in order to apply the correct dose according to what is indicated on the label of the product to be used.
   • Working pressure: pressure must be controlled, avoiding nozzle blockage or drying < working pressure > droplet size < risk of drift
   • Boom height: < boom height < risk of drift.
   • Working speed: < speed < possibility of drift
   • Anti-drift nozzles: advantage because they produce “large drops” but uneven spectrum.

2. Application Features 
   

   Drop size to be applied influenced by the nozzle

   • Extremely large droplets promote ENDO-DRIFT, do not spread adequately in the field and remain above the canopy or fall to the ground, but moderately large droplets may be suitable for systemic fungicides or systemic herbicides.
   • Small droplets applied with winds >15km/h produce EXO-DRIFT. It can also occur with volatile products with temperatures >25ºC and RH <50%.
   • Addition of anti-drift adjuvants: they thicken the spray solution and increase the size of the spectrum of applied drops.
   • Use of new herbicide formulations with low risk of drift.

2. Enviromental aspects

   These are the environmental conditions at the time of application, taking into account that the OPTIMAL CONDITIONS are:

   • Relative humidity, RH 45-65%,
   • Temperature <25°C
   • Wind: wind speed 5-15 km/hr and wind direction. DO NOT APPLY with wind speeds > 15 km/hr.

Slide

 

3. Buffer zones
   

   Good practices in peri-urban areas have particularities depending on the spaces and population that are to be protected, but in general terms they are the same as those that must be followed when using phytosanitary products in agricultural spaces.

   Buffer zone is the surface adjacent to certain protection areas that, due to their nature and location -for example peri-urban areas- require special treatment to ensure the conservation of the protected space, without hindering the activities carried out therein.

   The installation of buffer zones is one of the solutions proposals to minimize the possibility of contamination of sensitive areas to pesticides.

   Based on global experiences, the distances for the suggested buffer zones depend on the type of application and are suggested for terrestrial applications 100 meters and for aerial applications 200 meters, and may be modified according to the criteria of the acting professional, available technology, climatic conditions and the phytosanitary product used.

4. Vegetative barriers / Forest windbreaks
   

These barriers/windbreaks retain part of the drift from agricultural spraying, and are used to mitigate its effects by avoiding contamination of neighboring areas. They act by “attenuating” the drift.

According to Van Eimern et al. 1964, Living material structures, “windbreaks,” allow moisture to be conserved, protecting soil and plants while intercepting “airborne contaminants” and soil particles.

As an example, in the Alto Valle and Valle Medio areas of Argentina - producers of pome trees - "windbreaks" are used to protect fruit-producing groves. They contain species of poplars Populus nigra, hybrids Populus x canadensis, etc. They have a NW-SE orientation perpendicular to the prevailing winds.

As a result of pest control spraying, smaller droplets are lifted upward by the wind and could overcome the barrier. Larger droplets are attracted to the ground by the effect of gravity. In this way, part of the drift would not overcome the windbreak and would fall within the property where the spraying is carried out.

The optimum size of the sprayed droplets on the foliage of a fruit tree plant is between 40-100 microns (Matthews, 1987).

The optimum size of the sprayed droplets on the foliage of a fruit tree plant is between 40-100 microns (Matthews, 1987).

5. Anti-drift spraying and biological pesticides
   

   In soybean crops there are tests that have evaluated the control efficacy of the biological insecticide Bacillus thuringiensis on the pest Anticarsia with different spraying techniques; one with low drift and another with anti-drift (Massaro et. al., 2013).

   As a result, the effectiveness measured through caterpillar mortality was the same after spraying with an anti-drift technique using air-induction nozzles with large droplets, as with a low-drift technique using full cone nozzles, medium droplets with a coverage of 25 drops/cm2 in the middle part of the soybean crop.

   This combination of insecticide type and spraying technique has been proposed as ideal for use in peri-urban areas and near water sources, streams and canals. This practice can be repeated on any production crop to control the pest..

6. Design of specialized application equipment

   In Argentina, the Agricultural Mechanization Group of the INTA Concepción del Uruguay, Entre Ríos Experimental has demonstrated success at prototype level of a device with the capacity to change the size of the spray drop that comes out of its nozzles, without affecting the flow rate, depending on the place in the field where it is working, or according to the environmental conditions at the time. In this way, it is avoided that the product is applied more than one meter from the place where it should really impact.

   This design allows for no drift to occur when spraying agrochemicals under normal conditions (wind speeds of up to 15 km/hr, ambient humidity between 45 and 65%, and temperature not exceeding 25 degrees Celsius) since when working under “normal” conditions, drift may occur depending on the size of the drop, the location within the field, and gusts of wind.

Sources:

• Application of pesticides in critical areas. Agr. Eng. Rubén A. Massaro. INTA EEA Oliveros.
• ASAE S-572 Spray Tip Classification by Droplet Size, developed by the Pest Control and Fertilizer Application Committee; approved by the Power and Machinery Division Standards Committee; adopted by ASAE PM41. Pages 64-68
• https://bichosdecampo.com/inta-works-in-a-team-so-that-any-pulverizer-minimizes-drift/ Inta-Good Practices for the application of phytosanitary products / Brambilla V. Gomez Hermida M. Bogliani
• Field Bugs INTA Drifts in Application of Pesticides in Critical Areas
• Argentina Gob.ar Application of pesticides in critical areas. Agr. Eng. Rubén A. Massaro. INTA EEA Oliveros.
• FAO Manual for the Preparation of Pesticides CASAFE Manual for the Responsible Use of Phytosanitary Products 2020
• Bulletin of Disclosure N°41 ISSN 0328-3380 Guide for the proper use of pesticides and the correct disposal of their containers Agr. Eng. Fanny Martens INTA - Rural Extension Agency Tandil May 31, 2018
• INTA EEA Oliveros. Popular Article Keys to minimize drift Agr. Eng. Rubén A. Massaro
• Evaluation of plant barriers to mitigate spray drift Lic. Copes Walter EEA Alto Valle. INTA National University of Comahue Faculty of Engineering Master's Degree in Environmental Intervention. Environmental Engineering Orientation
• CASAFE Preventing drifts in the application of phytosanitary products
• Scientific report August 27, 2020 INTA officially recommends “strongly reducing” the use of agrochemicals
• INTA Reports Precise Applications: How to Control Drift
• Phytosanitary Manual Guidelines on applications in peri-urban areas Ministry of Agriculture, Livestock and Fisheries MAGyP, INTA, SENASA, MAGyA CFF, AACREA, AAPRESID, CASAFE, CIAFA, CPIA, FADIA, FeArCA and FAUBA.