24 February 2025, New Delhi: India’s agriculture sector is witnessing a technological shift with the increasing adoption of drones for pesticide application. The government has granted endorsement for several insecticides, fungicides, and herbicides, allowing their use via drone technology. While this move aims to enhance efficiency and reduce labor dependency, several critical concerns regarding efficacy, safety, and environmental impact remain unaddressed.
One of the primary concerns is the volume of water required for drone-based applications. Traditionally, most pesticide labels in India mandate high-volume spray applications, often ranging from 200 to 300 liters per acre. In contrast, drones typically operate with a significantly lower water volume, sometimes as little as 10 liters per acre. This drastic reduction raises questions about how bio-efficacy trials were conducted to determine the optimal water volume for drone applications. Experts argue that a lower water volume could lead to uneven distribution and inadequate pest control, potentially leading to resistance development and ineffective treatment cycles.
Concerns Over Spray Drift
Another pressing issue is spray drift under varying environmental conditions. The effectiveness of any pesticide application depends on its ability to reach the target crop while minimizing off-target dispersion. Factors such as wind speed, temperature, and humidity play a crucial role in drift dynamics. However, there is limited publicly available data on drift measurement studies conducted under different conditions. Without concrete evidence, concerns persist regarding unintended pesticide deposition on neighboring crops, non-target plants, and even human settlements.
Questioning Herbicide Efficacy in Drone Applications
Herbicide applications, in particular, require greater scrutiny. Pyroxasulfone 85 WG, a pre-emergent herbicide, is currently recommended for application on bare soil using 200 liters of water per acre in high-volume sprays. Whether the same formulation can be effectively applied using drone technology at a drastically reduced water volume (almost 90%) remains an open question. Similarly, Bispyribac Sodium 10% SC, a systemic post-emergent weedicide for rice, has been labeled for use with 300 liters of water per acre. If applied via drones at just 10 liters per acre, there are potential risks of higher localized concentrations that could adversely affect crop safety and soil microbiota.
Experts warn that high-concentration pesticide sprays could have unintended consequences for non-target organisms, including beneficial insects, aquatic life, and surrounding vegetation. Increased pesticide concentration in low water volumes might lead to phytotoxicity, affecting crop growth and yield. Despite these risks, there appears to be a lack of comprehensive evaluations addressing the long-term ecological impact of drone-based applications.
Calibrated Pesticide Delivery
Another technical limitation is the design of most agricultural drones in India. Unlike advanced models equipped with rotary atomizers or pressurized tanks that ensure a uniform droplet size and calibrated pesticide delivery, many drones currently in use lack these features. The absence of standardized spray booms means that multiple nozzles positioned under the rotors might cause overlapping spray patterns, leading to uneven pesticide deposition and wastage.
Furthermore, drone operators often prioritize covering more acreage over adhering to optimal spraying conditions. Reports suggest that some operators run their drones continuously, even during unfavorable weather conditions such as high winds or extreme temperatures, which can significantly affect the effectiveness of pesticide application and increase the risk of spray drift.
Need for Rigorous Scientific Assessments
With drones poised to become a mainstream tool in Indian agriculture, there is an urgent need for rigorous scientific assessments to establish best practices. Comprehensive trials on water volume requirements, drift control, droplet deposition, and pesticide efficacy under different climatic conditions must be conducted and made publicly available. Regulatory authorities should also consider enforcing stricter guidelines on drone specifications to ensure that only adequately equipped models are used for pesticide applications.
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