Cutting ants are the main pest in organic vineyards
Lack of control can lead to large production losses and even plant death. However, with the right techniques, the problem can be solved without using insecticides.
In the transition from conventional to organic wine production, producers face a pest that is not among the most mentioned: cutting ants. It is that species that cut leaves can end up with several vine plants in a few hours and, as this type of crop can not use synthetic insecticides, its control becomes challenging. However, there are several strategies that can be applied to minimize the damage.
Carla Dagatti, of the Laboratory of Phyto-pharmacy and Integrated Pest Management, of the Agricultural Experimental Station of INTA Mendoza, comments that since 2014 they began to receive consultations from wine producers alerted by the presence of cutting ants in their crops. From that, they began to develop research lines to know the pest in the Mendoza wine agroecosystem.
He added that they constitute a problem of increasing incidence in the vineyards of Mendoza, above all in those with organic management. New agricultural practices and the clearing of areas with native flora, he explains, have increased the presence of this pest. In young plantations, established after clearing the native vegetation, or in those with several years of cultivation and in full production, bordering on a native forest, the vineyards can suffer the complete defoliation of plants.
A vine plant after being attacked by ants / Courtesy INTA
The damage of the ants, he details, results in death of vines, delay in vegetative growth, rupture of apical dominance (the dominant bud is the one at the end of the branch), lower production, low profitability and additional costs for plant replacement, logistics and labor.
The researcher, who wrote her Master’s thesis on the diversity of ants in conventional and organic vineyards of Mendoza, detailed that leaf cutters (Attini) not only -as its name indicates- cut leaf fragments, but also flowers, fruits, stems and small pieces of branches of the surrounding vegetation. However, they do not eat this fresh material, but transport it to the anthill to grow the fungus from which they feed.
In the Mendoza vineyards are commonly found two species of cutting ants: Acromyrmex lobicornis and Amoimyrmex striatus, which are generalists, as they consume a wide variety of plants. The first inhabits environments with large thermal variations -such as mountains, deserts and steppes- and prefers moderate temperatures. Their nests usually have large external dumps and have a tumulus, dome or embankment, which minimizes environmental climate variability. Colonies, in general, are found under some tree or shrub, and their foraging paths, in the shade.
Amoimyrmex striatus, details Dagatti, is endemic to South America and specializes in collecting dried leaves. They just prune plants close to their nests and do not move more than 15 meters from them. The anthills do not have a tumulus and have several inlet mouths, linked by narrow channels and small pots up to two meters deep. The main mouth has the surrounding bare ground.
Although the fact that they cause damage to the vine is harmful to production, the forage activity of these ants can also have a positive effect on plants, since they remove seeds and fruits, facilitating their dispersion. In addition, by transporting and accumulating large amounts of plant material in their nests, they cause significant changes in soil nutrients, which can be beneficial for plant communities and other organisms.
However, the researcher recognizes that, being able to take advantage of most of the cultivated species, they are generally considered agricultural and forest pests. The attack on young plants causes a reduction in afforestation of up to 32% in height, 25% in circumference and 60% in timber production. Despite this, very little is known about the levels of damage in forests and vineyards in Argentina, and the factors that influence their preferences and intensity of defoliation at the local level.
THE TIME OF TRANSITION
Martín Uliarte, from the Sustainable Agrotechnology Area of INTA and specialist in organic vine management, agrees that the damage caused by ants is a problem that is presented to organic producers, especially at the time of transition; That is, when they abandon conventional production.
This, because, in general, the latter is associated with a monoculture, in which the soil is clean of other plants, to avoid competition with the vine. Thus, when they change the management mode and stop using insecticides to control ants, they begin to proliferate and only find the vine to feed.
Uliarte added that the biggest inconveniences occur in those farms surrounded by uncultivated field, since the vine is a plant more tender than the native vegetation and, therefore, more appetizing for this pest, mainly in the spring, when there is not so much food supply after winter.
At the Agricultural Experimental Station of INTA Mendoza made an experience with a conventional vineyard that transformed into organic and followed for eight years. The researcher commented that they had more problems with ants during the first four to five years.
As the transition involves not only ceasing to use agrochemicals, but also the incorporation of greater biodiversity, cover crops are established -herbaceous species that bring fertility to the soil and/or favor the appearance of beneficial insects- between the rows and under the vine. When it stops being alone, Uliarte details, and there are other offers of food, the damage that ants cause to production is reduced. Especially if you sow species that in spring are bloomed or with seeds.
On the other hand, they observed that, having more vegetation diversity, there is also a greater variety of ant species, so the cutters compete for space with others who do not prefer vineyards and reach a biological balance. Thus, although they may continue to attack some shoots in the vineyards, the effect is considerably reduced.
In the early years of the transition, he noted, from one day to the next they could observe several clearings in a row (in the Experimental Station they have a small surface). And the damage was concentrated in the spring. Uliarte considered that the key is to be patient and not pretend to solve the problem overnight, as can be done with the application of insecticides.
On the other hand, he indicated that there are insecticide products allowed for organic production and there are also those who use diatomaceous land. But, from their experience, and after trying some preparations, what gave them the best result was to have cover cultivation as an alternative feeding offer for ants and to favor the increase of biodiversity, which ensures a natural control of the pest. In fact, he pointed out, it is about living with her.
Uliarte added that the ant affects not only vineyards, but also a problem in horticulture, with some crops. Therefore, he pointed out that in each case, the phenology of plants should be analyzed, to offer more appetizing alternatives at the time when crops sprout. In addition, consider the possibility of supplementing with the application of some permitted product.
Alberto Cecchin, of the winery that bears the family name, states that the ants were many thousands of years before the crops advanced on the native mountain, so they are accustomed to the consumption of natural pastures. But if you remove them, they will attack what they have nearby. So the secret lies, he says, in leaving native vegetation. And if it is dry, much better, because otherwise, they have to dry it to be able to grow the fungus from which they feed.
The Cecchin Family has been dedicated to organic farming for over a century. Alberto comments that his grandparents worked in this way because, at the beginning of the last century, it was the only possible. But when chemicals became available, his grandfather refused to use them. While he is a naturist for 45 years, so he sustained this model of production that, in addition, contemplates that the tasks of the vineyard are performed at certain times of the lunar calendar (biodynamic). He claims that the farm in Coquimbito (Maipú) has anthills in the alleys, but the vines are not damaged.
Cecchin added that, although it has not been necessary for them, some natural fungicide can be used, because ants grow a fungus to feed and so the food they produce is eliminated. You can also use a preparation that changes the pH of the soil, which can generate an environment not conducive to the proliferation of the fungus. And even place simple broken rice around the anthill, as it produces a toxin that drives them away.
Carla Dagatti explains that the integrated management of cutting ants in cultivation contemplates prevention, permanent monitoring and control through low-risk strategies for the environment. To prevent ants from settling, it is advisable that the soil has plant cover as an alternative source of foraging during its reproductive period; i.e., spring and early summer.
This, because, on the one hand, a soil devoid of vegetation promotes the generation of anthills by the new queens. But on the other hand, plant cover helps the proliferation of biological controllers, such as fungi and insects, which on a greater or lesser scale can have an effect on ant populations.
The continuous monitoring in the plots, said the researcher from the Laboratory of Phyto-pharmacy and Integrated Pest Management, is a fundamental practice, as it provides information on the levels of presence and damage of the pest, and allows identifying control sites.
If the pest is already established, there are different control methods, among which the most common is the use of toxic baits and insecticide dusts. The products, he stressed, must be approved by Senasa for cultivation and for the pest. In the case of organically certified vineyards, the active ingredients and formulations authorised for this type of production must be used. In the following link you will find the permitted inputs in organic agriculture, which are updated monthly https://www.argentina.gob.ar/produccion-organica/lista/official-insumos-comercial.
As for the appropriate time of application, it indicated that at least one check must be carried out before implantation, in the case that the presence of nests of cutting ants is recorded in the ground. Once the plantation has been carried out, the control should be repeated at the pest presence points for at least the next two weeks and then monitor to evaluate the progress -or not- of the pest in the crop. The recommended frequency of these reviews varies depending on the number of ants and the species observed.
Ant baits are the most efficient and easy to handle control method. They should be applied to the sides of the paths of foragers, at a distance of 30 centimeters from the mouths of entry to the nests, not on them. If the nest has more than one active mouth, the dose should be distributed in proportional quantities. In general, 10 grams of bait are used for each mouth of the anthill, although the dosage depends on the species and the size of the colony (follow those recommended by the manufacturer). For organic vineyards, there are baits on the market with biological formulations (from Beauveria bassiana), Dagatti said.
Also, for the case of small and medium nests, powder formulations can be used, which are applied with an insufflation pump, which introduces a cloud of insecticide dust into the anthills. This type of product acts by contact; therefore, it is essential to pump enough dust to reach all the chambers of the nest and reach the queen. Dagatti pointed out that the activity of the treated colonies should be monitored and at 15 days, if necessary, repeat the application. As in the case of baits, there are powder alternatives to inflate in those certified organic vineyards. See https://www.argentina.gob.ar/produccion-organica/listado/oficial-deinsumos-comerciales.
The researcher commented that INTA advises wine producers on the identification, distribution and organic control of cutting ants. Also, studies have been developed on behavioral patterns and diets of both species -progress continues in this regard- and research trials are conducted on the efficacy of organic products for pest control.
In addition, vineyards have been surveyed with the presence of cutting ants in different districts of Mendoza: Altamira (San Carlos); Mayor Drummond and Agrelo (Luján de Cuyo); El Algarrobal (Las Heras); and Los Chacales (Tunuyán). As for future projects, they intend to advance in the study, production and evaluation of bioinputs for pest control, as well as in other biotechnology strategies.
An experience of coexistence with cutting ants
In the farm that Bodegas Argento has in Alto Agrelo (Luján) began 10 years ago to grow organic vineyards. In the property, which today has more than 230 hectares of vines, they bet not only to work without agrochemicals, but to maintain the environment as natural as possible, to achieve a better expression of varietals and terroir. However, they found that the cutting ants came to eat half a hectare in one night. But as they maintain the concept of seeking balance, they bet on trying to offer them other food alternatives.
Cecilia Acosta, Agricultural manager of the winery, pointed out that, although there is much talk of Botrana lobesia, this pest can be controlled with the technique of sexual confusion (with pheromones), so the main pest for organic vineyards are cutting ants. He added that there are winegrowers who started the transition from conventional to organic production and went back because they could not control the damage.
However, within the framework of their MatrizViva project, they chose to know the biological cycles of this pest and implement actions to reduce its pressure. Thus, they understood that cutting ants prefer bare soils to those with vegetation. And in fact, in several plots they have implanted herbs in the interfilars to study their contribution to the ecosystem, such as the control of nematodes or the attraction of beneficial insects; and in others they are analyzing the contribution of plants that grow spontaneously.
They also discovered that ants sit at the stake at the ends of the rows, so they are opting to use metal instead of wood. Another strategy to control the populations was to spread spores of a fungus different from the one they eat, to force them to migrate. And now they’re thinking of leaving biological corridors at the ends of the vineyards, so they can find food and nest outside the cultivated areas.
But they were also able to identify certain benefits that ants bring to the ecosystem, such as their mutual relationship with other insects (e.g., aphids); that those that are granivorous disperse seeds; that pollinate some plants; which feed other predators; that the large number of galleries in their nests favors soil aeration; and that they contribute to the degradation of organic matter.
Among other studies linked to MatrizViva, Bodega Argento has been developing, together with the INTA and the Chair of Green Spaces (of the Faculty of Agricultural Sciences) an analysis of the use of perennial flower herbaceous coverings, resistant to drought, in the interfilares. The research also aims to characterize the diversity of beneficial arthropods that contribute to pollination and pest control.
Emilia Mazzitelli, from the Entomology Laboratory of INTA Junín, commented that the goal is to know the functioning of agroecosystems and the adaptation of practices to local conditions, to promote production with low or no dependence on inputs external to the farm.
Historically, said Mazzitelli, the vineyards have been managed through an intense and continuous removal of plant coverings from their interfilars, which leads to a reduction in biological complexity. In this context, the incorporation of vegetation, such as floral bands, can favor the diversification of the ecosystem and the services provided by beneficial organisms, such as the regulation of pest insect populations.
It should be borne in mind that ecosystems self-regulate through a complex web of interactions between different species. Monocultures favor the appearance of pests because, since there is a large area of the same species, it becomes more vulnerable to attack, which generates a greater demand for the use of agrochemicals.
Although they are still in the evaluation stage, the agronomist said they have obtained some preliminary results, associated with the study of eight floral species implanted in interfilars of organic vineyards. The plant species Achillea filipendulina and Gazania repens were found to have a higher biodiversity associated with natural enemies (parasitoids and predators). In addition, parasitoids of the family Trichogrammatidae, which act as controllers of the vine moth, were found in Achillea filipendulina.
However, differences were observed between the species of natural enemies that are attracted by each floral species, so in the future we should think about a redesign of the vine cultivation, involving the use of corridors using a combination of different floral species. It is important to highlight, he said, that there are no recipes and that all design needs local adaptation for each particular producer.