Researchers adapt Spanish technology to combat fruit flies in vineyards

A clean technology used in Spain and Israel to control pests has been used successfully against fruit fly attacks on grapes. The so-called mass capture presents the simple principle of providing a food source that is more attractive to the adult insect than the grapes in the vineyard. The knowledge was adapted by Embrapa Grape and Wine (RS) for the management of the South American fruit fly (Anastrepha fraterculus) and is now available to producers. “The method guarantees production without insecticide residues, as the product is not applied to the fruits: it is simply placed in a trap that attracts adult insects, preventing them from damaging the fruits”, explains Marcos Botton, researcher at Embrapa who coordinated the research.

Controlling the species has been challenging, both for producers who adopt the conventional system, with the application of synthetic insecticides, and for organic insecticides, as the fruit fly is one of the main pests associated with vine cultivation, but which also it has other hosts, which guarantees its reproduction throughout the year. In addition to the search for cleaner and more sustainable methods, the Embrapa Uva e Vinho team looked for an alternative to replace traditional organophosphate insecticides, which are no longer authorized for use in vine cultivation in Brazil.

Fruit fly damage usually begins with injuries resulting from a wound in the grape berry, made by the female to lay her eggs. Then, due to the development of the larvae, galleries appear, which are generally associated with rot caused by microorganisms that infect the berries and increase losses in the pre-harvest period. According to the research team, in many cases the loss may be of some berries or even the entire bunch. In the first case, it is possible to thin the berries, removing those that are damaged, however, this practice requires additional labor, which increases production costs.

Embrapa Uva e Vinho, with partner institutions, has carried out several research works aimed at developing clean technologies for managing the pest, and mass capture was one of those that showed the best results. The technique consists of distributing a large number of traps per orchard area, in which adult insects are captured, reducing infestation in the vineyards. According to Botton, the technique has already been used for several years in Spain and Israel to control the Mediterranean fruit fly (Ceratitis capitata), an insect that also occurs in the Northeast region of Brazil and causes damage similar to that of Anastrepha fraterculus, main species of fruit fly that occurs in the southern region of Brazil.

The researcher reports that there have already been attempts in Brazil to use this technique to control fruit flies in different crops. However, they were not successful because the attractants used, mainly fruit juices, were inefficient and had to be replenished weekly in the traps.

After five years of research evaluating and adjusting management with a commercial animal protein as an attractant, the best results were achieved. This is because the adult fly needs to ingest protein compounds for the development and maturation of the eggs, which will give rise to larvae, that is, the survival of their descendants. The product also has high stability, meaning frequent replacement is not necessary, in addition to being selective, not harming other beneficial insects, such as bees.

Mass capture tests are successful in the field

For more than ten years, Clari Boff has been producing fine table grapes, such as Itália and BRS Morena, in Serra Gaúcha in the Municipality of Caxias do Sul (RS), one of the main horticultural hubs in the South of the country. She helped with the validation of technology and today celebrates the results. “With the help of Embrapa we managed to control the fruit fly and we are already thinking about starting organic cultivation”, reports the producer, who is responsible for an annual production of five thousand kilos of table grapes sold directly to consumers. She adds that the good results obtained throughout the experiments were decisive in expanding her production area

Before mass capture, the alternative for controlling fruit flies in the organic system was the individual bagging of grape bunches with paper bags, which despite being efficient, requires a lot of labor, which is increasingly scarce in the environment. rural. Placing traps and attractants for use in mass capture is also a technique that requires manual work, however, much less compared to bagging.

As it is a “zero waste” technology, mass capture is viable in production systems with high added value, such as table grapes, where consumer demand for waste-free products is greater, according to analysis by the researcher at Embrapa.

How mass capture works

The technique consists of installing 100 to 120 traps per hectare throughout the vineyard (the producer can increase the density on the most infested edges), using the hydrolyzed protein of animal origin inside as an attractant. After entering the trap, the insect can no longer find its way out and drowns, without the need to use chemical insecticides. There are traps that can be purchased, but, to make the technique cheaper to use, the research team teaches how to make homemade traps, reusing transparent soft drink packaging (see technical circular). “To use the packaging, simply make two seven-millimeter holes on opposite sides. Then place the attractant and hang the trap in the vineyard”, advises Ruben Machota Junior, post-doctoral fellow at Embrapa Uva e Vinho who is part of the research team.

He reveals that, initially, two-liter packages were recommended, however, research has demonstrated the same effectiveness when using 600 ml packages, bringing the additional benefit of using a smaller amount of attractant per trap. “It is necessary to place around 40% of the packaging volume, or around 250 ml of the food attractant. The product is stable and takes time to evaporate, but the producer must be careful and replace the liquid whenever necessary”, warns Machota Junior. It is estimated that approximately 500 ml of attractant are used per trap per harvest, considering a three-month cycle.

Traps must be distributed to achieve the recommended density of 100 to 120 units per hectare. The installation must be on the branches in the middle third of the plant, that is, approximately 1,5 m above the ground, in shadier places, which receive less sunlight, especially in the afternoon, thus reducing the evaporation of the attractant. .

Integrated Pest Management (IPM) Tool

Mass capture is one of the techniques that make up Integrated Pest Management (IPM) to combat fruit flies. In addition to this, the use of traps to monitor the pest and toxic baits (which is the association of a food attractant with an insecticide applied in strips, mainly on the edge of the orchards, seeking to reduce the infestation) are also recommended.

To carry out monitoring only, the same trap and attractant can be used, but in smaller numbers and only with the aim of identifying the level of insect infestation in the production area. When the fruit fly is detected in the vineyard, it is time to use mass capture and toxic baits.

Marcos Botton comments that, soon, producers will have other trap options to combat the pest, including new models and formulations of toxic baits that are more resistant to being washed away by rainwater. These technologies will help control different species of fruit flies, making pest management possible after the withdrawal of several organophosphate insecticides from the market.

According to the team, “zero waste” technologies, such as mass capture, are increasingly important in insect control, especially in Integrated Management. Scientists anticipate that other technologies aimed at producing fruit without waste and with minimal environmental impact are being researched and will soon be available. Among the new features, they mention automatic monitoring systems, infestation alerts, biological control and the sterile insect technique.