Recently, in the agriculture of the EU countries, there has been a tendency to reduce the use of plant protection products (hereinafter PPP). At the same time, there is a search for alternative preparations for especially dangerous and dangerous pesticides (class I, II), as well as active promotion in agriculture of biological control agents for pests, phytopathogens and weeds. For example, as part of the From Farm to Fork strategy (which is a key part of the European Green Deal, the strategy was published by the European Commission in May 2020), it is planned to reduce the use of chemical pesticides (their active ingredients) by 50% by 2030. According to the latest published data for February 2022, 934 active substances have been withdrawn their authorization for use in the EU, with 448 approved and 67 pending. It is reported that in 2022 the authorizations for 200 active substances will expire in the EU. At the same time, there is a risk of revocation of permits, including due to the complication and rise in the cost of the process of registration of active substances in the EU, for 34% of insecticides, 23% of fungicides, 35% of herbicides. In addition, the EU is gradually increasing the area occupied by the cultivation of organic plant products. So according to FAOSTAT statistics, for example, in the EU, the area of agricultural land occupied by organic farming in 2018 was 13016,254 thousand hectares, in 2019 - 13905,6276 thousand hectares; in 2020 - 14737,191 thousand hectares. For comparison, in the Russian Federation, in 2018 it amounted to 606,975 thousand hectares, in 2019 - 674,34 thousand hectares, in 2020 - 615,19 thousand hectares.
In the context of reducing the use of PPPs and the spread of an organic approach to growing crops, the issue of using modern technical means for ultra-low spraying is becoming important. One of these tools that have shown their effectiveness are unmanned aerial vehicles (hereinafter referred to as drones), equipped with equipment for spraying crop protection products and planting agricultural and woody plants.
Currently, the use of drones in crop protection is not legally allowed in the EU - EU directive (2009/128/EC) prohibits aerial spraying in EU countries. The ban on aerial spraying in practice limits the full use of drones in the EU as modern technical means for the application of plant protection products. In addition, the rigid scope of the existing ban does not contribute to the wide progress in the development of technologies in this field of plant protection. For this reason, many stakeholders in Europe are pushing for a revision and addition of this directive regarding the use of drones for spraying.
Currently, Asian countries, especially China, have made the greatest progress in the development of technology for the use of drones for spraying PPPs.
As for our country, in the Russian Federation, not all plant protection products have permission for use in aerial processing. To clarify whether a particular product has such permission, you can refer to the current version of the directory of permitted pesticides and agrochemicals (pesticides that have such permission are marked with the letter “A”). In addition, in accordance with the rules, in the Russian Federation, drones with a take-off weight of 0,25 kg to 30 kg are subject to mandatory registration.
For precise spraying of pesticides, the drones are equipped with a control system for the application of plant protection products. One of the advantages of their use is the possibility of introducing plant protection products with a finely dispersed droplet size at a low consumption rate. The finely dispersed droplet provides good coverage of plants, which allows effective control of plant pests at lower application rates, which is also important for preventing the emergence of resistant populations of plant pests. The undeniable advantage of applying PPPs using drones is a lower impact on the environment, on beneficial water and soil macro- and microbiota, as well as lower cost of treatments and less labor for farmers. But a big problem with the use of drones is the risk of drifting the spray to neighboring fields, where a crop sensitive to the drug used can grow. According to the study, the risk of spray drift can be reduced by lowering the flight altitude of the drone. Depending on the height of the crop being sprayed, the drone can operate at different heights (usually 3–10 m). In general, they are effective for ultra low aerial spraying of plant protection products at low altitude. An important aspect is that with this type of treatment, there is less consumption of the drug, since the drone sprays the pesticide only in those places where it is necessary (in the centers of development of diseases, weeds, and pests) with the capture of a small area in which organisms harmful to plants. At the same time, the dose of applying drugs can be adjusted depending on the degree of infestation/weediness of crops (i.e., adapt to changing conditions).
The high accuracy of PPP application by drones makes it possible to quickly and efficiently treat new foci of dangerous pests, especially when adjuvants are added to the solution.
Thus, according to practical testing, the effectiveness of morning (at 7 am) and evening (7 pm) treatment with a 6% pesticide solution (a.i. chlorantraniliprole + abamectin) with oil adjuvant Refei (China) using drones (China) against corn leaf cutworm Spodoptera frugiperda was above 90% 7 days after the first treatment and 7 days after the second pesticide treatment. At the same time, drones sprayed a pesticide solution from a height of 2 m, at a wind speed of 3 m/s. In addition, a relatively high efficiency of treatment of corn crops with a microbiological preparation of insecticidal action based on a suspension was noted. Metarhikum anisopliae (8 billion spores/g) - efficiency ranged from 37,1% with an average pest population of 16,6 caterpillars per 100 corn plants.
Also in the scientific literature it is described that the addition of a tank mixture of adjuvants SURFOM ADJ 8860; OXITENO (Brazil) has shown its high efficiency against powdery mildew on wheat. So, at a consumption rate of 15 l/ha of the drug, 150 ml/ha of the tank mixture of adjuvants SURFOM ADJ 8860 were added; OXITENO (Brazil), but even with a 1/3 reduction in the dose of the drug with the addition of a mixture of adjuvants SURFOM ADJ 8860; OXITENO (Brazil) protection against wheat powdery mildew remained high.
In addition, drones can be used to accurately release biocontrol agents from the air. So, according to a scientific study, drones were used to release a weevil from the air Rhinocomimus latipes against a weed Persicaria perfoliata, having the status of a limitedly distributed quarantine pest in European countries and widely growing in Asian countries.
The drones carried containers containing eight containers. Each container contained 20 adult insects. The bottom of the containers was made of a thin layer of clay, during the flight it collapsed, and the insects were released. The results of field studies showed that this method of releasing weevils did not significantly affect the survival and feeding capacity of R. latipes. Release efficiency R. latipes против Persicaria perfoliata ranged from 68,8 to 88,8%.
Also, according to a scientific study, drones can be used to release sterile male insects. This is a method of biological control, in which sterile males of the same species are released in large quantities into the territory where the pest is distributed. Sterile males mate with local females without producing viable offspring, which leads to a decrease in the pest population. In isolated places, even complete elimination of the pest can occur after a series of systematic releases throughout the territory. To ensure the effectiveness of the method and to minimize the mating of local males with local females, the ratio of sterile males to local males should be at least 1:10. In addition, the sexual behavior of sterile males should be similar to that of wild males. The huge advantage of this method is the minimal impact on the environment and non-target species, but in practice, the release of sterile insects is an expensive method, which also requires compliance with the technology, since in many cases insects can be damaged and even die during release without affecting the population. pest.
Summing up, we can say that the use of new technologies in agriculture has great potential both in the use of chemical plant protection products and in the biomethod. At the moment, the technologies for using drones in plant protection do not have a well-defined legal status in European countries, which somewhat slows down the progress of technology in this area. In Russia, the use of drones in plant protection is becoming increasingly popular, but it is important to note that the application of foreign experience in the conditions of our country requires a wide approbation of the technology on various crops, as well as the development and implementation of domestic adjuvants. It is also important to note that the development of domestic technologies for unmanned aerial vehicles will allow us to achieve the technological sovereignty of our country, including in the field of plant protection.
Maria Erokhova, junior researcher, VNIIF