Drones are capable of improving spraying to control soybean pests

Scientists from Embrapa Soja (PR) have proven the good performance of agricultural drones as spraying vehicles in controlling two important pests of soybean crops in Brazil: the brown stink bug and the false caterpillar Rachiplusia nu. The equipment was tested in the 2020/2021 harvest in comparison to other methods, such as tractors and knapsack sprayers, for applying chemical and biological products. Started in 2020, tests and evaluation of technical parameters for the use of drones are now being conducted to control Asian rust. The work is coordinated by researchers Samuel Roggia, Rafael Soares and Fernando Adegas.

In the case of the stink bug, research has shown that the use of drones is capable of reaching the pest in parts of soybean plants that are not normally reached by traditional spraying methods, such as the interior of the canopy (aerial structure of the plant) “ The combination of the sprayer's droplet spectrum - tip, working pressure and concentration of products in the syrup - and the effect of the movement of the drone's propellers (downwash) provided greater penetration of insecticide inside the soybean canopy, increasing control efficiency ”, highlights Roggia.

The tests indicated that drone spraying provided better insecticide deposition in the lower stratum of soybean plants. In the upper and middle strata of soybeans and deposits, it was equivalent to the other treatments evaluated.

The study used the same dose of insecticides per hectare in all types of spraying and showed greater spray deposits in tractor spraying (36 and 80 liters/ha) and backpack spraying (200 liters/ha) than by drone (ten liters/ha ). Roggia explains that to estimate the insecticide deposit at different heights of the soybean plant, a calculation was carried out considering the different concentrations of insecticide in the syrup. “Even though spraying with a drone provides less product deposit on the plant, when compared to tractor and backpack application, the spray is more concentrated, resulting in the same amount of insecticide applied per hectare”, explains the researcher.

Drone shows efficiency in biological control of caterpillars

Roggia also studied the different applications of the biological insecticide baculovirus in controlling the caterpillar Rachiplusia nu, which has not been efficiently controlled by Bt soybeans (genetically modified with genes from the bacteria Bacillus thuringiensis), due to the insect's resistance. According to the researcher, the application of baculovirus requires specific environmental conditions and an appropriate developmental stage of the caterpillars. “In this context, spraying with a drone represents an important operational advantage, because it allows applications to be carried out in situations where there are restrictions on spraying using a tractor, for example, right after a rain, such as very wet soil”, he highlights.

Roggia says that in the study, application was carried out with a spray volume of five and ten L/ha with a drone and in both cases the efficiency was greater than the costal application, carried out with a spray volume of 75 L/ha. The study used 50g/ha of the product VIRControl C.i., produced by the company Simbiose, from a strain licensed by Embrapa.

Comparative spraying for soybean rust control

With the aim of evaluating the spraying of fungicides to control Asian rust, researcher Rafael Soares also compared the different application methods: drone, trailed tractor and CO2-pressurized backpack. In the study, two sprays were carried out, based on climate monitoring, disease occurrence in the region and crop development stage (R2 and R5.1). “Asian rust severity assessments showed that there was no significant difference between spray treatments. However, periods of rainfall deficit during much of the harvest in the region did not favor the severe occurrence of Asian rust, which affected the trial and reached a severity of 26% in plots without fungicide application. Therefore, the tests are being repeated in the 2021/2022 harvest”, explains Soares.

Benefits of Drone Spraying

For researchers, the drone is a promising spraying tool and can bring immediate benefits, such as taking the applicator out of the field at the time of application, especially those using a knapsack sprayer; do not cause crushing of the crop; do not depend on soil conditions to enter the crop; use less water; do not use fossil fuels; speed of application in small areas; complement tractor and airplane spraying in rugged areas, with obstacles and in localized application, according to application maps, in the context of precision agriculture.

Although drone spraying is becoming commonplace, it still requires technical and agronomic information to improve its efficiency. “The objective is to obtain improvements in bottlenecks such as battery autonomy, the cost of equipment and spraying operations”, concludes Soares.

Improvement in product application technology

Technological evolution, especially precision agriculture, has led to the adoption of new tools for the spraying process, aiming for greater effectiveness and speed, at a lower cost and mitigating the risks of environmental and human contamination. The researchers reinforce that the spraying of phytosanitary products is an important tool for managing weeds, diseases and insects that attack the aerial part of soybeans.

In the case of diseases, the research was focused on Asian rust, the crop's biggest phytosanitary problem. In terms of pests, the tests were aimed at controlling the brown stink bug, the main insect pest of soybeans, and the false caterpillar Rachiplusia nu, which despite being sporadic, is an important defoliator. “The stink bug has a high potential for damage, as it directly attacks reproductive structures, which can cause abortion or poor formation of pods and grains, reduction in the mass and quality of harvested grains and seeds, in addition to leaf retention and losses during production storage” , explains Roggia.

The researchers explain that the efficiency of phytosanitary product application technology is defined by the use of scientific and technical knowledge that provides the correct placement of the biologically active product on the target of interest. “This process should preferably involve only the necessary quantities of product, in an economical way and with minimal drift to avoid reaching other areas located in the vicinity of the planned target”, says Soares. In this sense, different aspects of the technology for applying phytosanitary products that can impact the spraying process were evaluated, such as different flow rates, spray tips, deposition and distribution of drops.

Regulation of the use of aircraft

As of 2017, the National Civil Aviation Agency (Anac) regulated the use of remotely piloted aircraft (popularly known as drones or vants) in Brazil. The Brazilian Special Civil Aviation Regulation (RBAC) nº 94/2017 presents the rules that aim to make operations with these types of equipment more viable and safe. This regulation complemented the standards related to drone operations, already established by the Airspace Control Department (Decea) and the National Telecommunications Agency (Anatel).

In a complementary manner, the Ministry of Agriculture, Livestock and Supply (Mapa) published Ordinance No. 298, of September 22, 2021, which establishes rules for the operation of remotely piloted aircraft intended for the application of pesticides and the like, adjuvants, fertilizers, inoculants, correctives and seeds. “As a result, as of October 2021, operators of application companies or rural producer users have been required to register on the Integrated System of Agricultural Products and Establishments (Sipeagro) platform to treat crops with drones. agricultural. Furthermore, to work in the field, the applicator must be over 18 years old and have a remote aeroagricultural application course (CAAR), taught by an entity or teaching company authorized by Mapa”, says Soares.