Drones used to better disperse beneficial insects

Vergelegen Wine Estate near Somerset West in the Western Cape, is testing the use of drones to release beneficial insects in its fight against leafroll virus.

The test is facilitated by SkyBugs, a partnership between FieldBUGS, which supplies the predatory insects, and agri-tech company Aerobotics, which collaborates with a network of drone pilots to disperse the insects accurately.

According to a press statement, Vergelegen uses both predatory wasps (Anagyrus Vladimiri and Coccidoxenoides Perminutus) and ladybird beetles (Cryptolaemus Montrouzieri) to keep mealybugs, which spread leafroll virus, under control.

The predatory wasps, which are attracted by a pheromone released by female mealybugs, are released during the first stage of control, followed with the selective distribution of ladybirds, which can eat 100 to 200 mealybugs a day. The insects are dispersed using drones while they are still pupae, to hatch several days later depending on the weather.

The first SkyBugs drone dispersal at Vergelegen took place in October last year, with a total of five dispersals planned over 130ha, depending on test results. The test should be concluded by the end of the first quarter of 2024.

Ruan Erasmus, technical support specialist at FieldBUGS, said the insects are released from a drone flying 30m above a vineyard block.

“Beneficial insects are traditionally dispersed by purchasing compostable tubes of insect that are hung on vines. Releasing the insects aerially is much more effective, as predatory wasps fly no more than 90m daily. It also allows for the release of insects onto high trees near the vineyard, where mealybugs normally escape detection.”

Erasmus added that the use of insect pupae on plastic film saved the cost of tube packaging and offered better value for money.

The drone released the insects by using a motor-driven mechanism equipped with a cartridge and a drawnout plastic file, effectively releasing the insects onto the vines. Each flight covered up to 20ha, after which the drone was landed, and a new battery and cartridge of insects were inserted.

Erasmus said that one could never completely eradicate mealybugs, but the use of beneficial insects helped to keep them under control.

Rudolf Kriel, Vergelegen’s viticulturist, said that the drone delivery of beneficial insects was the latest phase in a longterm, holistic sustainability programme.

“Our records show that Vergelegen has under 0,05% of leafroll virus infestation in red varieties, and less than 0,3% in white varieties, which is exceptional for vineyards of 20 to 25 years of age.”

Their management programme consisted of the uprootment of badly infected red wine vineyards, and the replacement of these with virus-free plant material, as well as the testing of white wine cultivars that did not readily show the effects of the virus.

Vergelegen’s alien vegetation clearing programme, through which 2 200ha of land was cleared by 2019, had also provided additional natural solutions. Kriel pointed out that as indigenous fynbos returned, it attracted increasing numbers of birds and insects, including an abundance of ladybirds. –