Exploratory Use of the DJI AGRAS T30 in Lithuania to Control the Spread of Invasive Heracleum Sosnowskyi

 

Sosnowsky's Hogweed, scientifically known as Heracleum sosnowskyi, poses a significant threat as an invasive species in the Baltic States, Belarus, Russia, Ukraine, Poland, and Germany. Originally introduced to Lithuania as a fodder plant in the 1950s, it quickly gained popularity due to its stunning appearance and large inflorescence. Unfortunately, its cultivation in the 60s and 70s led to its rapid spread, and it became uncontrollable in the late 80s and early 90s.

 

 

Figure 1. The area of the Baltic states where the spread of Heracleum sosnowskyi is prevalent. A Plant with a Dangerous Secret

 

One of the most alarming aspects of Heracleum sosnowskyi is the chemical it produces called furanocoumarin. This potent allergen is found in high concentrations throughout the entire plant. The juice of this plant contains compounds that sensitize the skin to sunlight, causing severe burns ranging from the first to third degree. These burns often manifest as watery blisters that are difficult to heal, and can even leave long-lasting brown pigmented spots.

 

 

Figure 2. Fully developed Heracleum sosnowskyi plant, ripening its seeds.

 

 

Figure 3. Damage to the skin caused by contact with the juices of Heracleum sosnowskyi and exposure to UV light. Source: Wikipedia

 

 

Clever Biology to Grow Above its Native Neighbors

 

The relentless spread of Heracleum sosnowskyi is fueled by multiple factors. Firstly, its prodigious seed production allows for dispersal through various means. Additionally, its quick germination and ability to outgrow and crowd out other plants contribute to its invasive nature. Notably, each plant yields tens of thousands of seeds annually, with larger plants releasing up to 100,000 seeds within a 4-meter radius. Moreover, an astonishing 95% of these seeds can remain viable for several years. Consequently, this invasive species overshadows and displaces native plants. Within a short span of time, a once thriving landscape bursting with diverse wild plants can be transformed into a monoculture dominated by towering 3-4 meter tall Heracleum sosnowskyi plants.

 

 

Overcoming the Persistence of Heracleum Sosnowskyi: a Challenging Task

 

The eradication of Heracleum sosnowskyi poses a significant challenge. This invasive species has the remarkable ability to regrow from its roots, even after repeated cutting. In fact, it can continue to sprout for up to 13 years, demanding constant maintenance in cleared areas. Managing this plant requires unwavering attention, repeated treatments, and a vigilant approach.

 

The steady spread of Heracleum sosnowskyi is not limited to open spaces. It poses a threat to areas surrounding reservoirs, rivers, roads, and forests as well. Controlling the plant's growth along rivers is particularly challenging due to the transport of its seeds by tides. Furthermore, the use of pesticides is restricted in water basin regions. As a result, this invasive species continues to expand its territory, particularly in locations difficult to access with ground machinery like abandoned meadows, woodlands, and rivers.

 

 

The perils of Manual Intervention:

 

Traditionally, until this point, the spread of this invasive species has been controlled manually – using backpack sprayers and trimmers. This poses serious health risks for work crews, who are exposed to furanocoumarin. The plant's juice, when released during cutting, can cause harm to the skin and eyes, necessitating precautions such as washing thoroughly and avoiding sunlight.

 

At present, the spread of Heracleum sosnowskyi has surpassed human control and has proliferated throughout the Baltic states. Abandoned lands that were previously used for economic activity contribute to its expansion. Specialists estimate that the weed's minimum annual growth is approximately 10%, and it is believed that the plant has invaded over 18,000 hectares in Latvia alone.

 

 

A UAV Solution From the Sky

 

Nando Droid, a DJI Agriculture Authorized Dealer based in Lithuania, rose to the challenge of combating this hazardous invasive weed. In this experimental study, a DJI Agras T30 UAV was utilized to spray a hectare of land overrun by Heracleum sosnowskyi in Latvia's Tukuma Novads region (coordinates 56.780811, 23.158854). The chosen test location perfectly simulated the conditions of a typical infestation, as the area was sloped and wooded, rendering it inaccessible to ground machinery.

 

On the 27th of June, Nando Droid performed the spraying while the plants were blooming. Although the weather conditions were cloudy, with wind gusts up to 4 m/s, the average wind speed during the operation remained below 3 m/s, with an ambient temperature of 16°C.

 

Figure 4. Healthy Heracleum sosnowskyi plants during the day of the operation. Author of photo – recipient of Nando Droid drone spraying services “AGRO Konsultaciju Centrs”.

 

DJI Agras T30

 

The Agras T30 is a powerful agriculture spraying drone, capable of carrying a liquid payload of 30L. It was a solid solution for this task because of a few of its features, including:

• The T30’s strong propeller downwash that pushed the sprayed mist down, penetrating the thick canopy of the plant and ensuring a uniform, focused distribution of the chemical.

• The T30’s ability to fly just a few meters above the plants, minimizing any chemical drift.

• The T30’s spherical radar system eliminated blind spots and kept the drone safe from collisions throughout the manual flight.

 

 

Chemicals

 

To effectively eradicate the invasive plants, the product used for spraying was Cortevas' Zypar - a systemic herbicide containing florasulam as the active ingredient. The recommended dosage for agricultural commercially grown crops is 1 liter per hectare. However, due to the Heracleum sosnowskyis’ growth stage, and this being the first time conducting such a study, the norm was increased by 50% to ensure maximum efficacy and complete eradication of the invasive plants.

 

To guarantee the safety of surrounding farmlands and woodlands, Nandos' anti-drift agent - Targetum[1] - was used at a concentration of 0.2% of the total volume. The prepared solution's spraying volume was 20 liters per hectare.

 

 

Manual Flight

 

Due to very difficult terrain and number of trees in the area to be sprayed, the Nando Droid team operated the UAV in manual mode, maintaining a height of 3 meters above the target plants. The trajectory of the UAV can be seen in Figure 5.

 

Because the client who ordered the spraying, AGRO Konsultaciju centrs, was interested in purchasing a T10 for this task, Nando Droid filled the T30 tank to about 10-15 liters per flight, to more accurately simulate the time duration it would take to perform this task using the T10. The full operation took about 1 hour to complete, from first takeoff to landing, with a total of 4 flights performed, using 3 batteries.

 

Figure 5. The trajectory of the T30 Agras UAV flown in manual mode. As can be seen from the map, there are several trees in the operation area limiting the ability of the UAV to work in automatic mode.

 

 

A Precise, Timely Intervention

 

Three days after the Agras T30 applied Zypar to the weeds, there was an immediate and noticeable effect, as can be seen in Figure 6.

 

Figure 6. Results of spraying Heracleum sosnowskyi with Zypar 3 days after application. Author of photo – recipient of Nando Droid drone spraying services “ AGRO Konsultaciju Centrs”

 

Two months later, the Nando Droid team revisited the application field to assess the intervention’s impact on the invasive Heracleum sosnowskyi plants, as depicted in Figure 7. The spraying effectively eliminated all targeted plants before they could produce seeds.

 

Figure 7. Results two months after spraying Zypar in difficult terrain using DJI Agras T30. Author of photo – recipient of Nando Droid drone spraying services “ AGRO Konsultaciju Centrs”

 

It’s worth noting that the neighboring fields were unaffected by chemical drift. As shown in Figure 4 on the map, the field adjacent to the Heracleum sosnowskyi was a commercially used agricultural plot for growing legumes. Despite the high concentration of Zypar, the crop remained unaffected and later successfully harvested. This demonstrates the precise nature of the Agras T30, and indicates that Targetum can effectively minimize the risk of chemical drift.

 

A Satisfied Client

 

Bojan RAJČEVIČ , CEO of AGRO Konsultaciju centrs, the company that ordered the field to be sprayed, remarks that the operation was a success because the plants did not manage to produce any viable seeds this year. He was also so impressed with the ease of operation that he immediately purchased a DJI Agras T10 for future jobs relating to the eradication of Heracleum sosnowskyi. He notes that every year he gets orders for around 50 to 100 hectares of sosnowskyi to be eradicated. Before having the ability to use drones, his crews found it difficult to access areas that are completely overgrown with the invasive plant. The crews would only spray the outer edges of the affected areas, allowing the plants deep in the infested area to further produce seeds. But not anymore. Thanks to the solutions offered by DJI his and his crews’ task of eradicating this invasive species became much easier.

 

 

Conclusion

 

In conclusion, the invasive species Heracleum sosnowskyi presents a significant ecological threat in various parts of Europe. Its rapid growth, high seed production, and the potent allergen it produces pose substantial challenges to both humans and the environment. Traditional methods of control have proven insufficient, often exposing workers to health risks. However, the innovative use of drone technology, as demonstrated by Nando Droid's experimental study, offers a promising solution. This successful trial with the Agras T30 indicates that drones could play a pivotal role in managing and controlling the spread of invasive species in the future. As we continue to grapple with the ecological impacts of such species, it is imperative to explore and invest in technological solutions that offer effective, efficient, and safer alternatives to traditional methods.

Special Thanks to Nando Droid: - www.nandodroid.lt