In recent years, as a researcher focused on innovative agricultural technologies, I have witnessed the rapid expansion of citrus cultivation, particularly for varieties like Wogan and Maoguan, driven by high socio-economic benefits. However, this growth has been accompanied by escalating challenges from pests and diseases, exacerbated by large-scale farming and changing ecological conditions. Citrus crops are inherently susceptible to various pathogens, and in regions with high temperatures and abundant rainfall, such as Southern China, diseases like citrus canker become particularly rampant. Farmers often adopt intensive strategies, such as spraying pesticides at every new shoot stage and before or after rain, leading to frequent applications and high chemical usage. Concurrently, common pests including citrus leaf miners, citrus red mites, citrus psyllids, and aphids can cause severe damage, resulting in leaf and fruit drop that impacts yield, necessitating year-round control measures. During the summer shoot period, which coincides with rainy seasons, efficient pesticide application is critical to prevent outbreaks. Traditionally, pest control in citrus orchards relies heavily on chemical agents applied via backpack sprayers or high-pressure sprayers, methods that are labor-intensive, inefficient, and increasingly untenable amid rural labor shortages. This often compromises the timeliness and quality of applications, underscoring the urgent need for more effective施药方式. Enter agricultural drones—these unmanned aerial vehicles offer high efficiency and low operational costs, effectively bridging the labor gap. By 2018, agricultural drones in China had entered a phase of规模化应用, with numbers and technology领先 globally, covering over twenty million hectares annually across crops like rice, wheat, corn, and cotton, and extending to various forestry plants. In this context, I conducted a study to evaluate the efficacy and economic benefits of agricultural drone spray applications for pest and disease control, as well as summer shoot management, in flatland Wogan orchards during the夏梢期. This article delves into our findings, emphasizing the transformative potential of agricultural drones in modern citrus cultivation.
Our experiment was carried out in 2019 in a three-year-old Wogan orchard located in a flat area with medium soil fertility and good maintenance practices. The trees were healthy and uniform, with minimal pre-existing pest or disease issues. We established a demonstration zone and a control zone, each covering 1 hectare, with consistent田间管理措施 throughout the trial. The demonstration zone employed agricultural drone spray applications, facilitated by a professional company that provided the equipment, pesticide mixing, and operation. We used the XAG P30 2018 model agricultural drone equipped with a SUPERX 3 RTK flight control system, a liquid capacity of 15 L, centrifugal atomization nozzles producing 120 μm droplets, and a spray width of 3.5 m. Field parameters included a flight height of 4.5 m and a water volume of 1.5 L per 667 m². In contrast, the control zone utilized traditional担架式喷雾施药, operated by three workers simultaneously, with a water volume of 300 L per 667 m². The agricultural drone offered significant advantages in terms of automation and precision, as illustrated by the operational setup. During the summer shoot period in May, we conducted three preventive spray applications. The first application on May 9, under cloudy conditions (20–24°C, northeast wind 1–2级), targeted citrus red mites, citrus canker, and summer shoot control. The second on May 17, during多云 weather (27–35°C, south wind 1–2级), focused on citrus red mites and citrus canker. The third on May 22, with阵雨转多云 conditions (25–30°C, northeast wind 1–2级), addressed citrus canker and summer shoot control. To mitigate high-temperature stress, applications were scheduled before 10 AM or after 4 PM on hot days. The pesticides used included 12% flumetralin EW, 8,000 IU/μL Bacillus thuringiensis SC, 3.2% abamectin EC, and 25% paclobutrazol SC, among others. The dosages for each application method are summarized in Table 1, highlighting the reduced volumes required by the agricultural drone.
| Application Method | May 9 Dosage per 667 m² | May 17 Dosage per 667 m² | May 22 Dosage per 667 m² |
|---|---|---|---|
| Agricultural Drone Spray | Bacillus thuringiensis 65 mL + Abamectin 40 mL + Paclobutrazol 150 mL + Flumetralin 200 mL +飞防助剂 30 mL | Copper calcium sulfate 150 g + Beta-cypermethrin 65 mL + Abamectin 40 mL +飞防助剂 30 mL | Paclobutrazol 200 mL + Flumetralin 250 mL + Copper calcium sulfate 200 g |
| 担架式Sprayer | Bacillus thuringiensis 600 mL + Abamectin 200 mL + Paclobutrazol 1000 mL + Flumetralin 750 mL + Copper calcium sulfate 300 g + Beta-cypermethrin 200 mL | Copper calcium sulfate 300 g + Beta-cypermethrin 200 mL + Abamectin 200 mL | Paclobutrazol 1000 mL + Flumetralin 750 mL + Copper calcium sulfate 300 g |
The efficacy of pest and disease control was assessed through rigorous surveys. For citrus canker, after new shoots matured on June 10, we sampled five新梢 from three trees in each of five方位 within both zones, examining每片叶子 for lesion counts. Disease severity was graded on a 0–9 scale: 0 for no lesions, 1 for 1–5 lesions, 3 for 6–10 lesions, 5 for 11–15 lesions, 7 for 16–20 lesions, and 9 for over 21 lesions. The disease leaf rate and disease index were calculated using standardized formulas. The disease leaf rate (DLR) is given by:
$$ \text{DLR} = \left( \frac{\text{Number of diseased leaves}}{\text{Total number of leaves surveyed}} \right) \times 100\% $$
And the disease index (DI) is computed as:
$$ \text{DI} = \left[ \frac{\sum (\text{Number of plants at each grade} \times \text{Representative value of the grade})}{\text{Total number of plants surveyed} \times \text{Highest representative value}} \right] \times 100 $$
Our results, presented in Table 2, demonstrate that both application methods effectively controlled citrus canker, with only sporadic occurrence of grade 1 diseased leaves. Notably, the agricultural drone spray showed marginally better performance, with a lower disease leaf rate and disease index compared to the担架式sprayer. This underscores the precision and coverage achievable with agricultural drones, even at reduced chemical volumes.
| Test Area | Application Method | Leaves Surveyed | Diseased Leaves | Disease Leaf Rate (%) | Disease Index |
|---|---|---|---|---|---|
| Demonstration Zone | Agricultural Drone Spray | 909 | 20 | 2.20 | 0.24 |
| Control Zone | 担架式Sprayer | 918 | 23 | 2.51 | 0.28 |
Summer shoot control was another critical aspect of our study. Before夏梢抽发, two spray applications were administered at an 11-day interval to suppress new shoot growth. Ten days after the second application on June 2, we调查新梢数量 on ten marked branches per zone. The agricultural drone spray resulted in 106 new shoots across ten sample trees, while the担架式sprayer had 133 new shoots. The control efficacy of the agricultural drone was enhanced by 20.3%, calculated as:
$$ \text{Control Efficacy Increase} = \left( \frac{\text{New shoots in control} – \text{New shoots in drone zone}}{\text{New shoots in control}} \right) \times 100\% = \left( \frac{133 – 106}{133} \right) \times 100\% \approx 20.3\% $$
This significant improvement highlights the ability of agricultural drones to deliver agents more effectively to tree canopies, where new shoots predominantly emerge, thereby optimizing growth management.
The economic benefits of employing agricultural drones are substantial. We analyzed the costs per hectare for each application method, factoring in药剂费用 and机械（人工）费用. For the agricultural drone, each application incurred a rental fee (including equipment and labor) of $225 per hectare and an average药剂费用 of $606.75 per hectare. In contrast, the担架式sprayer required人工费用 of $450 per hectare (based on three workers covering 0.8 hectares daily at $120 per worker) and an average药剂费用 of $2,220 per hectare. The detailed cost breakdown across the three applications is provided in Table 3. Comparing the two methods, the agricultural drone saved an average of $1,613.25 per hectare in药剂费用 and $225 per hectare in人工费用 per application, culminating in total savings of $1,838.25 per hectare per application. Over multiple applications in a season, these savings amplify, making agricultural drones a cost-effective solution for large-scale citrus orchards.
| Application Method | Chemical Cost May 9 ($/ha) | Chemical Cost May 17 ($/ha) | Chemical Cost May 22 ($/ha) | Mechanical/Labor Cost May 9 ($/ha) | Mechanical/Labor Cost May 17 ($/ha) | Mechanical/Labor Cost May 22 ($/ha) | Total Cost May 9 ($/ha) | Total Cost May 17 ($/ha) | Total Cost May 22 ($/ha) |
|---|---|---|---|---|---|---|---|---|---|
| Agricultural Drone Spray | 669.75 | 280.50 | 870.00 | 225 | 225 | 225 | 894.75 | 505.50 | 1,095.00 |
| 担架式Sprayer | 3,720.00 | 675.00 | 2,715.00 | 450 | 450 | 450 | 3,720.00 | 1,125.00 | 3,165.00 |
Safety and additional pest control outcomes were also monitored. Post-application observations revealed no phytotoxicity symptoms such as leaf or fruit drop, or damage to fruits and leaves in the agricultural drone zone. Moreover, common pests and diseases during the tender shoot stage—including citrus leaf miners, citrus red mites, aphids, citrus psyllids, citrus anthracnose, and moss—were effectively suppressed, indicating comprehensive protection afforded by the agricultural drone spray. This aligns with the inherent advantages of agricultural drones: they enable uniform droplet distribution and penetration into canopy layers, reducing the risk of under- or over-application that can occur with manual methods.
The broader implications of our study extend beyond immediate efficacy and cost savings. Agricultural drones represent a paradigm shift in precision agriculture. Their high efficiency allows daily coverage of 12–15 hectares, far surpassing traditional担架式sprayers, while minimizing labor intensity and addressing rural workforce shortages. From an environmental standpoint, the reduced chemical and water usage associated with agricultural drone applications lowers pesticide residues and mitigates pollution, contributing to sustainable farming practices. Compared to alternative aerial methods like helicopter spraying, which requires specialized pilots and airspace clearance, agricultural drones offer greater flexibility, lower operational barriers, and reduced costs. They can be operated via remote control or smartphone apps, with many manufacturers providing free training, democratizing access for farmers. Additionally, agricultural drones are not constrained by daylight, enabling night operations to capitalize on rain-free intervals during雨季—a crucial advantage in regions like Southern China. Their compact size and agility allow navigation around obstacles like power poles or buildings, eliminating施药“盲区”常见 in helicopter or manual applications. Furthermore,智能规划路线 capabilities prevent漏喷 or重复喷药, enhancing accuracy and reducing药害风险. For summer shoot management, which often involves targeting tree tops, agricultural drones provide superior access compared to labor-intensive manual spraying, ensuring more effective control.
However, the adoption of agricultural drones is not without challenges. Current pesticide formulations are often designed for high-volume sprayers, and some agents with low solubility may not be ideal for drone applications, potentially affecting efficacy. There is a need for专用药剂 tailored to飞防, optimizing混配体系 to prevent interactions that could diminish active ingredient potency. In densely canopied orchards, direct飞防 might not adequately reach the middle and lower tree layers, necessitating pruning to improve通风透光性—this not only enhances agricultural drone performance but also reduces pest habitats and overall control costs. Technological limitations also exist: most agricultural drones are electric, with payload capacities constrained by battery life, limiting single-flight coverage. Despite this, ongoing advancements in battery technology and drone design are rapidly addressing these issues. The trend toward专业化和标准化 in agricultural drone operations promises to further integrate them into mainstream agricultural植保.
To quantify the long-term benefits, consider a seasonal model where multiple applications are required. If we define the total seasonal cost savings (SCS) as:
$$ \text{SCS} = n \times (\text{Savings per application}) $$
where \( n \) is the number of applications per season, and savings per application is $1,838.25 per hectare, then for a typical regimen of 6 applications, SCS would be:
$$ \text{SCS} = 6 \times 1838.25 = 11,029.5 \text{ dollars per hectare} $$
This substantial economic incentive, coupled with enhanced pest control efficacy, makes agricultural drones a compelling investment. Moreover, the environmental benefit can be expressed in terms of reduced chemical load (RCL) per hectare:
$$ \text{RCL} = \sum_{i=1}^{n} (\text{Chemical volume}_{\text{traditional}} – \text{Chemical volume}_{\text{drone}}) $$
Using data from Table 1, for example, on May 9, the担架式sprayer used 600 mL of Bacillus thuringiensis per 667 m², while the agricultural drone used 65 mL—a reduction of 535 mL per 667 m². Scaling up, this translates to significant decreases in overall agrochemical deployment.
In conclusion, our study unequivocally demonstrates that agricultural drone spray applications are not only feasible but highly advantageous for citrus pest and disease control during the summer shoot period. The agricultural drone achieved comparable or superior results in managing citrus canker and suppressing summer shoots, while delivering remarkable cost savings through reduced chemical and labor inputs. The agricultural drone’s efficiency, precision, and adaptability address critical gaps in traditional methods, positioning it as a cornerstone of modern智慧农业. As technology evolves, with improvements in battery life, payload capacity, and formulation compatibility, agricultural drones are poised to become the predominant mode of agricultural植保, revolutionizing crop management across diverse agroecosystems. Future research should focus on optimizing pesticide blends for drone use, developing canopy penetration strategies, and conducting long-term studies on environmental impact. For now, the evidence is clear: integrating agricultural drones into citrus cultivation practices offers a sustainable, economical, and effective path forward, ensuring resilient orchards and enhanced productivity in the face of evolving agricultural challenges.
Reflecting on this experience, I am convinced that the widespread adoption of agricultural drones will transform pest management paradigms. Their ability to operate in diverse conditions, from flatlands to undulating terrains, and their scalability from smallholdings to large estates, make them versatile tools. The agricultural drone is not merely a piece of equipment; it represents a shift toward data-driven, precision agriculture where every drop of pesticide is utilized optimally. As we continue to refine these technologies, collaboration among researchers, manufacturers, and farmers will be key to unlocking their full potential. In essence, the agricultural drone is more than a solution to labor shortages—it is a catalyst for a more efficient, sustainable, and profitable agricultural future.