High tech is being combined with ancient natural remedies at one of South Africa’s best-known wine farms, where buzzing benefactors are helping to keep the vineyards pest-free.
Vergelegen wine estate in Somerset West is testing the use of drone-delivered beneficial insects to control pests in its vineyards.
The goal is to achieve fewer vine disease and higher quality grapes, ensuring that in decades to come, Vergelegen’s winemakers can produce excellent wine from healthy vineyards that are currently 20-25 years old – a great asset as the fruit gets better over time.
The 324-year-old estate is working with South African venture, SkyBugs, a partnership between FieldBUGS, which supplies the predatory bugs, and agritech company Aerobotics, which collaborates with a network of drone pilots to disperse the insects accurately.
The first SkyBugs drone dispersal took place at Vergelegen in October last year and a total of five dispersals, depending on test results, should be concluded in the first quarter of 2024. Some 130 hectares of vineyards will receive beneficial insects via drones.
Ruan Erasmus, FieldBUGS technical support specialist, says the first stage of the programme involved scouting and data assessment. The actual method of insect release involves flying a drone 30m above a vineyard block.
The drone releases insects by utilising a motor-driven mechanism equipped with a cartridge and a drawn-out plastic film, effectively releasing the insects onto the vines. Each flight covers up to 20 hectares, after which the drone is landed, and a new battery and cartridge of insects are inserted.
The insects are dispersed while in the pupa life stage (between immature and mature insect) and hatch after several days, depending on the weather.
The target of these tiny heroes is mealybugs, which spread a disease known as leaf roll virus. This disease is much more apparent in red wine cultivars, but also affects white wine cultivars.
Leaf roll virus diminishes the quality and volume of the harvest and eventually the vines become uneconomical and must be uprooted – yet another burden for a sector that is already under severe financial constraints.
Vergelegen uses both predatory wasps (Anagyrus Vladimiri and Coccidoxenoides Perminutus) and ladybug beetles (Cryptolaemus Montrouzieri) which are indigenous to South Africa. The first stage is distributing predatory wasps, which are attracted by a pheromone released by female mealybugs.
This proactive measure is supplemented with the selective distribution of ladybugs, which can eat 100-200 mealybugs daily.
FieldBUGS, which has about 15 insect types in its arsenal, sources the predators used at Vergelegen from insectaries in Piketberg and Tzaneen.
Vergelegen viticulturist Rudolf Kriel says using the drone delivery of beneficial insects is the latest phase in a long-term, holistic sustainability programme.
“Our records show under 0,05% of leaf roll virus infestation in red varieties, and less than 0,3% in the white varieties,” says Kriel.
“From a grapevine leaf roll virus point of view, it is exceptional to have vineyards of this age (20-25 years) that are essentially virus-free. Vergelegen has been the pioneer in many ways for addressing leaf roll in the South African wine industry, and has been implementing these control strategies since these blocks were established.”
The Vergelegen team has worked closely with Professor Gerhard Pietersen of the Agricultural Research Council – Plant Protection Research Institute, at the University of Pretoria, for 25 years. Professor Pietersen sought an agricultural property where he could demonstrate the scientific and commercial value to the wine industry of managing, and even eradicating, leaf roll virus.
The programme to control mealybugs at Vergelegen was implemented in three phases: planting new, intact vineyards; uprooting badly infected red wine cultivar vineyards and replanting them; and testing and treating white wine cultivars that, apart from chardonnay and semillon, do not readily show the effects of the virus.
“Vergelegen planned to replace 25 hectares of citrus with vineyards and, accordingly, in 2002 the first completely “clean’ vineyard was planted. These vines were regularly tested and any infected vines were removed,” says Kriel. “The mealybug virus has virtually been eradicated at that first, newly-planted vineyard.”
Vergelegen’s alien vegetation clearing programme has provided additional natural solutions. In a programme believed to be the largest privately funded alien vegetation clearing undertaking in South Africa, some 2200 hectares of land were cleared by 2019.
As indigenous fynbos has returned, it attracts increasing numbers of birds and insects, including an abundance of ladybugs.
Erasmus reports that South African farmers are advanced in harnessing data to assess and manage risk, and there is growing interest in biological control of pests, especially in the Western Cape from which 80% to 85% of fruit is exported. Farmers want to improve their yields, and avoid chemical residue on fruit, to meet strict European and Fairtrade environmental standards.
Beneficial insects not only suit vineyards, but can also be used by producers of citrus, dates, apples, macadamias, avocados, pears, blueberries, cannabis, strawberries and various vegetable crops.
Farmers considering drone dispersal of insects should cover a minimum of 50 hectares, advises Erasmus. Costs range from R650-R1500/hectare, which includes scouting, insect release, technical support and reporting.
Beneficial insects are traditionally dispersed by purchasing compostable tubes of insects which are hung in vines. Drone dispersal, on the other hand, ensures more effective distribution and coverage, says Erasmus.
Predatory wasps fly no more than 90m daily, so drone dispersal improves the likelihood of the wasps locating mealybugs. Beneficial insects can also be released onto high trees near vineyards, where mealybugs normally escape detection. The use of insect pupa on plastic film saves the cost of tube packaging, and offers better value for money.
“One can never completely eradicate mealybugs, but it is possible to control them,” concludes Erasmus. “Vergelegen, an influential estate, has set the standard for mealybug control and it’s been a pleasure working with a team that shares the same philosophy regarding pest management.”
Matt Davis, head of mapping operations at Aerobotics, says: “Vergelegen is one of our largest clients and it’s been exciting to work with them, in a programme that has provided good proof of concept for using this method of drone-delivered beneficial insects. The estate has been most receptive to using technology in their quest for pest-free vineyards using natural methods.”