Drones and the art of spraying fruit crops in South Africa

A South African drone services start-up is backing agricultural drones to soon overtake manned aircraft and other conventional means as the best crop spraying option to deal with the menace of fruit flies that pose danger to the prospects of fruit farming in the country.

Cape Town-based Integrated Aerial Systems (IAS) recently demonstrated the effectiveness of drone spraying in destroying the fruit fly at an orange farm in Citrusdal in the Western Cape province.

And so confident were they of their solution that they did the demonstration as a comparison to the use of manned aircraft, which was used to spray the adjacent part of the field.

“Currently, several techniques are used for controlling fruit flies in South Africa, IAS explained in a report.

“One of the common techniques is bait spraying. The bait, usually containing attractants and an insecticide such as Spinosad, lures the fruit flies that are subsequently killed after feeding on the insecticide-laced droplets.

“In South Africa, common baits are GF-120 and Cura-Fly.

“Along with the bait, programs involve traps that monitor the fruit fly levels. Baiting programs are an essential component of integrated pest management (IPM) strategies used to reduce or remove fruit fly pests from vineyards and fruit trees.”

And it was those bait chemicals that the company loaded onto a drone and deployed it to cover its allotted part of the orange field.

“We were tasked to bait 30 hectares of orange trees covered by protective nets. The end goal is to compare the results to the neighbouring orchard which was sprayed by a manned aircraft, and see how drone-based applications fare.

“To test the efficacy of drone spraying, we used Ultraviolet (UV) dye in part of the baiting mixture to assess the distribution as well as the droplet size.

“Once it was dark, the pilot went into the field with a UV light and found that we had coverage in all the correct spots, and the droplet sizes were full and large despite the coverage of fruit trees by nets. Thus, these results were very promising and exactly what we hoped for.”

While acknowledging that the use of drone technology in this area of agriculture is in its fledgling days yet, IAS forecasted that there was likely to be a boom in the use of drone spraying on fruit trees.

As it is, the company says there are already some farmers that have made crossed the divide from using manned helicopters to working with drones, and results so far have been really encouraging.

In IAS’s argument, that is because drones give the farmers the below advantages:

  • Precision and Targeting: Drones provide precise application capabilities, allowing for accurate targeting of baiting zones. This precision minimises the wastage of bait, ensuring that the treatment is concentrated where fruit flies are most active, thus enhancing the effectiveness of the control method.
  • Access to Difficult Terrain: Drones can easily access difficult-to-reach spots, ensuring comprehensive coverage of the entire orchard or vineyard.
  • Speed and Efficiency: Drones are capable of covering large areas quickly. This efficiency is particularly beneficial in larger orchards and vineyards, where time is a crucial factor during fruit fly outbreaks.
  • Customisation and Adaptability: Drone-based baiting programs can be easily adapted to changing conditions, such as shifts in fruit fly populations or variations in weather. The flexibility to modify flight paths and application rates ensures that control efforts remain effective over time.
  • Consistency: Drones offer consistent and uniform application, reducing the risk of human error that can occur with manual methods. This consistency ensures that bait and insecticide are distributed evenly across the target area.

“Drone-based baiting programs align with modern agricultural practices, prioritising efficiency, precision, and reduced environmental impact,” IAS said.

“This ensures that farmers take a sustainable and responsible approach to pest management while getting the best results possible. In doing so, drone-based programs aid the significant South African fruit market in retaining its global market share in fresh fruit exports.

“As technology continues to advance, this method holds the potential to revolutionise pest management strategies in the agricultural industry.”

The South African fruit sector is particularly vulnerable to the effects of fruit flies, given its prominent position as the second-largest producer of fruit in the southern hemisphere. This industry plays a pivotal role, responsible for exporting approximately 36 percent of total fruit exports from the global south, making it the largest exporter in the region.

With over 200,000 hectares of cultivated land, the sector also serves as a vital source of employment, generating about 300,000 on-farm jobs, according to statistics from the South African fruit body, Fruit SA

South Africa is home to several unwelcome fruit fly species, including the Natal fruit fly (Ceratitis cosyra) and the Mediterranean fruit fly or Med-fly (Ceratitis capitata), with the Med-fly having a larger host range and being more tolerant to weather conditions as opposed to the Natal Fruit fly which prefers wetter conditions.

According to Fruit SA, the Med-fly is one of South Africa’s destructive agricultural or largest distribution pests. They have successfully established themselves in the different South African climates across the country.

They infest over 200 types of fruit and vegetables and are particularly damaging to South Africa’s largest fruit production, including pome fruit (apples and pears), stone fruit (apricots, peaches, nectarines), citrus, guava, and grapes. It is estimated that crop losses and pest control costs resulting from fruit flies amount to tens of millions of Rands per year in the Western Cape alone

Their life cycle can stretch to four weeks, and they may live for up to three months.  The females can lay up to 800 eggs that short time, thereby causing considerable damage if not prevented or controlled.

The Natal fruit fly on the other hand is an invasive species that cause widespread damage by the females puncturing or “stinging” the ripening fruit when they lay their eggs just under the fruit skin, leaving the larvae to develop in the fruit and inserting fruit decaying bacteria.

Within two days, the larvae hatch, tunnel into the fruit and cause considerable damage before signs are even evident on the outside of the fruit. Further down the line, the quality of the fruit decreases substantially, and the fruit cannot be sold.

Once fully developed, the maggots drop to the ground to pupate in the soil and transform into the adult fly.

“Fruit flies exert a substantial economic impact on global agriculture, leading to significant financial losses for commercial fruit production and driving up costs for farmers due to the expenses associated with control and management.”


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