In modern agriculture, the management of pests like the European corn borer (Ostrinia nubilalis), cotton bollworm (Helicoverpa armigera), and peach pyralid (Dichocrocis punctiferalis) is critical for ensuring crop yield and quality. These pests infest corn ears and stalks, leading to significant losses and increased susceptibility to fungal infections. As a researcher focused on sustainable pest control, I investigated the use of Trichogramma wasps released via crop spraying drones to combat these issues. This approach leverages biological control agents to reduce reliance on chemical pesticides, aligning with integrated pest management principles. The adoption of spraying UAV technology offers potential improvements in efficiency and coverage compared to traditional methods, such as manual release of Trichogramma cards. In this study, I conducted a field experiment to evaluate the effectiveness of drone-based release systems, comparing them with manual release and conventional chemical treatments. The primary goal was to assess parasitism rates, pest control efficacy, reduction in ear mold, and overall yield impact, while emphasizing the advantages of crop spraying drone applications in large-scale farming.
The experiment was designed to simulate real-world conditions in a corn field, where pests naturally occur. I selected a homogeneous plot with consistent soil type and corn variety to minimize external variables. The corn was planted at a density of 5,000 plants per 667 m², and standard agronomic practices were followed, except for the pest control interventions. The treatments included: a drone release area of 7.3 hectares, a manual release area of 3.3 hectares, a chemical control area of 3.3 hectares, and a control area of 1,334 m² with no pest management. The drone used was a modified DJI T20 crop spraying drone, which automatically dispensed Trichogramma card balls containing a mix of Trichogramma species (primarily Ostrinia nubilalis and Trichogramma chilonis). Each ball held 2,000 wasps, and the release rates were set at 12,000 wasps per 667 m² for the first application and 8,000 wasps per 667 m² for the second. The spraying UAV operated at a height of 3 meters above the crop canopy, a speed of 5 m/s, and a swath width of 30 meters, ensuring even distribution. For manual release, workers hung Trichogramma cards on upper leaves at about 1.5 meters height, with the same release rates. The chemical treatment involved applying 5% emamectin benzoate and lambda-cyhalothrin via a DJI T40 spraying UAV at 20 mL per 667 m², with a spray volume of 2 L per 667 m². The release timing was synchronized with pest life cycles; based on monitoring, the first release occurred when 20% of second-generation corn borers had pupated, followed by a second release 10 days later. To assess outcomes, I measured release efficiency, egg parasitism rates, pest incidence, ear mold, and yield. All data were analyzed using Duncan’s new multiple range test for statistical significance, and formulas were applied to calculate key metrics. For instance, the parasitism rate was determined as: $$ ext{Parasitism Rate} (\%) = \left( \frac{ ext{Number of Parasitized Eggs}}{ ext{Total Eggs Surveyed}} \right) \times 100 $$ Similarly, control efficacy for plant damage and pest density was computed using: $$ ext{Plant Damage Control Efficacy} (\%) = \left( \frac{ ext{Control Area Damage Rate} – ext{Treatment Area Damage Rate}}{ ext{Control Area Damage Rate}} \right) \times 100 $$ and $$ ext{Pest Density Control Efficacy} (\%) = \left( \frac{ ext{Control Area Pest Count} – ext{Treatment Area Pest Count}}{ ext{Control Area Pest Count}} \right) \times 100 $$ During the study, meteorological conditions were recorded, showing average temperatures of 25.2°C, precipitation of 189.5 mm, and sunshine hours of 435.3 h, which were slightly above historical averages and could influence pest behavior and wasp activity. The use of a crop spraying drone in this context not only enhanced operational speed but also allowed for precise placement of biological agents, reducing human labor and potential errors. For visual reference, an image of the spraying UAV in action is available here: Link.
The results demonstrated significant differences in release efficiency between methods. The crop spraying drone completed the release over 7.3 hectares in 56 minutes with two operators, yielding an efficiency of 1.02 minutes per 667 m² per person. In contrast, manual release required five workers and 116 minutes, resulting in an efficiency of 11.6 minutes per 667 m² per person. This indicates that the spraying UAV was approximately 11.37 times more efficient than manual methods, highlighting its potential for large-scale applications. Such efficiency gains are crucial for timely interventions in pest management, as delays can reduce the effectiveness of biological controls.
| Treatment | Parasitism Rate (%) | Statistical Significance |
|---|---|---|
| Drone Release | 81.50 | A |
| Manual Release | 83.42 | A |
| Chemical Control | 3.28 | B |
| Control | 19.22 | C |
As shown in the table above, egg parasitism rates were highest in the manual release area (83.42%), closely followed by the drone release area (81.50%), with no significant difference between them. Both were significantly higher than the control area (19.22%) and the chemical control area (3.28%), which had the lowest rate due to pesticide impacts on natural enemies. This underscores the compatibility of Trichogramma releases with biological control and the detrimental effects of chemicals on parasitoid populations. The high parasitism in drone-treated areas suggests that the spraying UAV can effectively distribute wasps without compromising their viability, possibly due to the protected environment of the card balls and the drone’s stable flight parameters.
For pest control efficacy, the overall plant damage and pest density results are summarized in the following table. The plant damage control efficacy ranged from 59.56% to 64.34%, with the drone release showing the highest value, though differences among treatments were not statistically significant. However, pest density control efficacy varied more markedly, from 71.35% to 79.34%, with both drone and manual releases outperforming chemical control significantly. This implies that while all methods reduced visible damage, biological controls via spraying UAV or manual means were more effective at suppressing pest populations overall.
| Treatment | Plant Damage Rate (%) | Plant Damage Control Efficacy (%) | Pest Density (per 100 ears) | Pest Density Control Efficacy (%) |
|---|---|---|---|---|
| Drone Release | 32.33 | 64.34 | 27.33 | 77.41 |
| Manual Release | 33.67 | 62.87 | 25.00 | 79.34 |
| Chemical Control | 36.67 | 59.56 | 34.67 | 71.35 |
| Control | 90.67 | — | 121.00 | — |
Breaking down the efficacy by pest species revealed nuanced differences. The table below details the residual pest counts and control efficacies for European corn borer, cotton bollworm, and peach pyralid. In the control area, pest composition was 63.64% corn borer, 6.61% cotton bollworm, and 29.75% peach pyralid. After treatments, the drone and manual releases showed high efficacy against corn borer (83.12% and 84.42%, respectively) and peach pyralid (72.22% and 75.00%), significantly better than chemical control. However, for cotton bollworm, the chemical treatment achieved 66.63% efficacy, outperforming the drone (45.88%) and manual (50.00%) releases, which had lower and statistically similar results. This variation may relate to differences in pest behavior, such as oviposition patterns or susceptibility to parasitism, and highlights the need for integrated approaches when multiple pests are present.
| Treatment | Corn Borer Count | Corn Borer Efficacy (%) | Cotton Bollworm Count | Cotton Bollworm Efficacy (%) | Peach Pyralid Count | Peach Pyralid Efficacy (%) |
|---|---|---|---|---|---|---|
| Drone Release | 13.00 | 83.12 | 4.33 | 45.88 | 10.00 | 72.22 |
| Manual Release | 12.00 | 84.42 | 4.00 | 50.00 | 9.00 | 75.00 |
| Chemical Control | 20.00 | 74.03 | 2.67 | 66.63 | 12.00 | 66.67 |
| Control | 77.00 | — | 8.00 | — | 36.00 | — |
The reduction in ear mold was another critical outcome, as pests like corn borer facilitate fungal infections by damaging ears. The control area had an ear mold rate of 31.33%, while all treatments significantly reduced this to 7.00–8.33%, with no major differences among them. This demonstrates that both biological and chemical controls can mitigate secondary issues like mold, which directly impacts grain quality and safety. The use of a spraying UAV for Trichogramma release proved equally effective as manual methods in this regard, reinforcing its utility in comprehensive pest management.
Yield analysis further supported the benefits of pest control. The table below presents the yield data, where all treatments resulted in higher yields than the control, with increases of 6.51–8.06%. The drone release area achieved the highest yield of 717.30 kg per 667 m², equivalent to an 8.06% increase, though statistical tests showed no significant differences among treatments. This suggests that while pest control boosts productivity, the choice of method may not drastically alter yield outcomes in the short term, but the spraying UAV approach offers additional advantages in efficiency and environmental sustainability.
| Treatment | Yield (kg/667 m²) | Increase Over Control (%) |
|---|---|---|
| Drone Release | 717.30 | 8.06 |
| Manual Release | 714.80 | 7.68 |
| Chemical Control | 707.00 | 6.51 |
| Control | 663.80 | — |
In discussion, the efficiency of the crop spraying drone stands out as a major advantage. The 11.37-fold improvement over manual release translates to substantial time and labor savings, which is crucial for scaling up biological control in extensive farming systems. Moreover, the comparable efficacy in parasitism and pest control between drone and manual methods indicates that the spraying UAV does not compromise biological agent performance. The lower efficacy against cotton bollworm in drone and manual releases could be due to its scattered oviposition behavior, making it less accessible to Trichogramma wasps, whereas chemicals provide broader coverage. This points to the importance of tailoring control strategies to specific pest ecologies, perhaps combining drone-released Trichogramma with targeted insecticides for resistant pests. The cost aspect is also noteworthy; in this trial, drone release cost approximately $40 per 667 m², compared to $15 for chemical control, but economies of scale could reduce this disparity in larger applications. Additionally, the environmental benefits of reducing pesticide use—such as preserving beneficial insects and minimizing residues—add long-term value to the spraying UAV approach. From a practical perspective, the deployment of a spraying UAV for Trichogramma release involves optimizing parameters like flight altitude, speed, and ball distribution to enhance parasitoid survival and dispersal. Future research could explore hybrid systems where drones monitor pest populations and adjust release rates dynamically, leveraging advances in precision agriculture.
In conclusion, this study demonstrates that using a crop spraying drone for releasing Trichogramma wasps is a viable and efficient method for controlling corn pests like European corn borer and peach pyralid, with performance similar to manual release but superior operational efficiency. The spraying UAV technology facilitated rapid, large-scale distribution of biological agents, resulting in high parasitism rates, effective pest suppression, reduced ear mold, and improved yields. While chemical controls showed strength against certain pests like cotton bollworm, the overall benefits of drone-based biological release—including environmental safety and labor reduction—make it a promising tool for integrated pest management. As agriculture moves towards sustainability, the adoption of spraying UAVs for such applications could revolutionize pest control practices, and I recommend further investigations into cost optimization and multi-pest strategies to enhance their adoption.