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José Eduardo Petrilli Mendes

Bracell Forestry Operations Manager


A practical view of the management of ants

It has long been known that leaf-cutting ants are of great importance in the food chain, with the potential to cause severe energy losses in the primary production of vegetables, whether cultivated or not. With estimates of more than 50 million years of existence, ants have been present on earth about 20 times longer than humans. This time of existence, evolution and adaptation makes these insects, as well as their societies, highly evolved and resilient, being one of the key factors to be considered in their management.

Social insects, leaf-cutting ants are known as “the first farmers” on the planet, due to the mutualistic symbiosis they have with the fungus they cultivate for their food. As a result, they cut parts of vegetables and carry them inside their nests, for later chopping and distribution in the fungus gardens, for the development of the fungus. This behavior and habit derives its commercial importance, and may cause damage to human interests, especially related to cultivated plants.

It is important to put this into context so that we can better understand the complexity involved in managing leaf-cutting ants, especially leaf-cutting ants, in eucalyptus plantations, as we are dealing with the main pest of the crop and, in my view, the most complex to manage. The damage caused by leaf-cutting ants to eucalyptus plantations is known and variable, being directly influenced by the age and productivity of the plantations, the season of the year, the density and size of the nests present in the area, the incidence, severity and frequency of defoliation, usually being a consequence of inadequate management in relation to the presence of the pest in the area of operation and its surroundings.

Defoliation by leaf-cutting ants can lead to plant death, especially in young plants, but it is also common in adult trees, especially in areas with high infestations, high frequencies of large nests and successive defoliations. Productivity losses in relation to ant attacks are also well known, and may exceed 50% reduction in the final harvested volume. Given the economic importance and complexity of ants management in eucalyptus forest plantations, what should be done to prevent damage caused by this pest to plantations?

The initial step, of vital importance for the successful management of leaf-cutting ants, is to start production free of the presence of nests. Getting off to a good start can take some time, but it is better than having to manage large nests of pre-existing ants in established plantings. Once the planting is carried out in areas without relevant infestations, the rounds or transfers during the establishment and initial growth phase of the seedlings are essential to prevent new activities by leaf-cutting ants from impacting the survival and uniformity of the forest.

In the initial phase of planting, different ant management strategies have been used by eucalyptus forest planters. Currently, the market offers ant killer options that provide different modes of action and forms of application, in addition to some options for forest managers. It is worth remembering one of the basic premises of Integrated Pest Management, which is to maintain the environmental balance at the best possible level, without allowing pests to cause damage to the crops of interest. This is a universal concept, applicable to any crop, wherever it is cultivated, and it cannot be different with our eucalyptus plantations.

In the forest maintenance phase, aiming at the best possible level of environmental balance, without damage to the forests, the recommended and usual practice in most plantations is to monitor infestations and defoliation caused by leaf-cutting ants. Normally, at this stage of the plantation, ants are the most relevant species in economic terms. The species or subspecies of ants vary according to the geographic region, however, the monitoring techniques currently applied cover all species present and potentially harmful in Brazilian eucalyptus plantations.

The most common form of monitoring is still walking on the ground, aiming at identifying and classifying nests by size classes, quantifying scouts and identifying defoliation classes in plants. This information supplies a decision-making system, where matrices with combinations of infestation classes, nest sizes and defoliation levels lead to the best management decision for the evaluated area, which can be applied at the stand level, or at a more comprehensive level, as required. desired by the forest manager.

In addition to defining the need for combat, the product to be used, the form of application, the best path in the field for the application according to the identified infestation patterns can be configured as outputs from the monitoring system. These possibilities are available for contracting or can be developed by the forest manager himself.

New remote monitoring techniques are being applied in tests or on a pilot scale, so we should evolve in this regard in the coming years. It should not be necessary to mention that combating ants needs to be considered a specialized service, which must be carried out by trained and well-prepared people, as the combat action must be effective for controlling nests and effectively reducing pest infestations. . In addition to specific technical training for this activity, the applicable Regulatory Norms for Rural Work must be met. Still on this aspect, discipline and rigor in complying with combat recommendations should be evaluated as key operational performance indicators . Route deviations need to be corrected immediately.

The last phase of management, known as pre-cut or pre-harvest combat, normally occurs in the last year of standing forest, before harvesting, and is one of the main activities related to the success of plantation reform, as it is strictly linked to the “ start production free from the presence of ant nests”, as already mentioned. One or more combats may be necessary in this phase, according to the pattern of infestation in each area. If it is necessary to carry out sequential operations for the effective control of the infestation, the time interval between them must respect the known information about the bioecology of the ants, otherwise, the manager will have the false sensation that the situation has been resolved and he may have problems in establishing the new one forest.

Regarding research in relation to the application of new techniques and products, there are possibilities to advance in monitoring techniques, in the offer of products of biological origin, in formulation technology, such as the encapsulation of actives, among others. However, even when new solutions are available, discipline and rigor in handling leaf-cutting ants must be maintained, as this is the only way to succeed in controlling this important pest, which is highly adapted to the conditions suitable for plantations. forests in Brazil.