Applied From The Skies

The techniques of pesticides application have unfortunately not been developed to the same extent as the pesticides themselves. Yes, we have sophisticated turbine engines and air conditioned cabins, yet in most instances we continue to install crude hydraulic spray nozzles from the mid-1950s to atomize the products.

Learned In The Fields

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Low volumes can provide superb coverage, provided that the applicator adjusts his application equipment to match the droplet size to the product and conditions. In my view, it is an absolute necessity to conduct application tests with the equipment and products to identify the optimal adjustment to obtain consistently good results. We need to abandon the old concept of gallons of water and to make tailor-made applications to match the prevailing conditions.

There are several tools available to measure the efficiency of product application. This includes mylar cards, water sensitive cards, fluorescent tracer products, and chemical analysis of the deposit.

Each of the methods has an academic value, however the only true measurement that matters on an economic basis is “Did the product work?”

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Why is this relevant? It is a well established fact that the pyrethroid insecticides have not been performing as well as expected in many cases, especially within the US, yet they continue to deliver excellent performance and are well known for their “rapid knockdown” throughout Argentina and Brazil. The reason being is that these products work by contact and ingestion action with no vapor effect, which means that for good results, they must be delivered to the target insect.

In the US, practically all product labels specify high volumes of water such as 2 to 5 gallons per acre (g/a). This means that the products are highly diluted with water, and furthermore, when applied in high volumes of water, most of the product is delivered in large spray droplets, resulting in grossly inadequate crop penetration and minimal contact with the insects. This means that growers have to wait for the insects to find the chemical.
However, in Argentina and Brazil, most of the applicators apply the products using low and very low volumes (ULV), typically applying insecticides at 2 to 10 liters/hectare (L/Ha), or 0.1 to 1 g/a, with the products mixed with a non-volatile oil under adverse conditions to protect against evaporation loss.

Rust Proofing

The same principles apply to the control of Asian soybean rust disease, since for adequate control we must have excellent crop coverage, and this can be best achieved through low volumes utilizing oils and adjuvants to minimize evaporation losses and to maximize crop coverage. During the past four seasons, very large areas of soybeans in Argentina and Brazil have been treated successfully using low volumes of 2 to 4 g/a using ground equipment and 0.5 to 1 g/a by aircraft with results significantly superior to those obtained with high volumes.

The key to success is the production of uniform droplet size — not volume of water. In seeking to obtain increased spray coverage, it is far more important and more economical to decrease the droplet size than to increase the spray volume. Many entomologists/agriculturalists have believed that higher volumes mean better coverage; this is erroneous, and results in poor control with inconsistent results in addition to higher application costs.

Here is what our field work in South America has taught us:

  • Lower volumes have been proven to be more effective than high volumes in Brazil and Argentina for all categories of application including insect control, rust control, and crop desiccation using glyphosate. With my personal grower and custom applicator clients, many millions of hectares were successfully treated last season using volumes of 10 L/Ha or less, with the best results for rust control with aircraft around 5 L/Ha. With ground equipment, the best results are with 20 to 40 L/Ha depending on the forward speed of the equipment.
  • Low volumes are more effective for several reasons, however the most important is probably that the chemical ingredient is more concentrated, enabling higher efficacy, such that one spray droplet may be adequate to kill a particular insect.
  • For mechanical reasons, it is easier to atomize a lower volume of liquid using smaller spray nozzles.
  • Rotary atomizers have been proven to be more effective in producing the necessary narrow droplet spectrum. How­ever, they require skill and experience in operation.
  • When applied in oils, the chemical deposits have longer residual action as they are more resistant to wash-off by rainfall.
  • Aircraft are more productive, since less time is wasted refilling with water.
  • Productivity is further improved due to weather conditions, because more hectares can be covered before mid-day when the weather usually starts to become less favorable.

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