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Mariane Aparecida Nickele e Wilson Reis Filho

Consultant Funcema/Embrapa Florestas and Researcher at Epagri/Embrapa Florestas


Quequens in planted forests: an undersized problem

The leaf-cutting ants known as saúvas and quenquéns are among the main forest pests in Brazil and, if not controlled, can make the implantation of a forest economically unfeasible. The quequens disperse through breeding flocks, which occur once a year during the spring, but, in addition to the flock, they can also disperse through migration, which they do very frequently, looking for more favorable places for the development of the its colonies.

The ants, because they have larger and more showy nests due to the loose soil they deposit on the soil surface, are more studied and are a reason for greater concern than the quenquéns, as they attack plants at any stage of development, especially in eucalyptus plantations. However, the quequens also have a great potential for damage, but only in initial plantings, and the foraging area of an adult colony can reach a radius of up to 80 meters and, therefore, can attack a significant number of newly planted seedlings.

There is occurrence of leaf-cutting ants throughout the Brazilian territory, and it is rarer to find nests of ants in areas with altitudes above 800 meters, a factor that does not limit the occurrence of quequens. Quenquens are more frequent than ants, and it is possible to find areas where only quequens are found, but an area with only ants is not common. The nests of some quequen species, such as Acromyrmex subterraneus, although they are not very deep, they are underground and with loose soil on the soil surface, and may be confused with young nests of ants.

To confirm the genus, however, it will be necessary to observe the number of spines on the thorax of the workers, which are four or five pairs in the case of the quequens, while the ants have only three pairs. The quequens, depending on the species, can also build superficial nests covered with heap of cisco, as the Acromyrmex species does. crassispinus. There is also the species of quequem Acromyrmex niger, which nests underground, but without loose soil on the soil surface, which makes it difficult to monitor. It is common to find an average of 35 nests of pine moths per hectare in pine plantations aged close to three years.

This occurs, even in plantations where pre-and post-planting combat was carried out, when a large number of nests were initial, which have low external activity, making it difficult to find them. In this way, the nests can reach three years of age, when there are already breeders, and cause an increase the infestation of leaf-cutting ants in adjacent areas. It is only around 15 months of age that the nests of the moths are easier to visualize in the field, allowing localized control.

It is easier to monitor an area for ants infestation than for ants, as all ants nests can be found from the initial nest stage, when their radius of action is still small. The species of quequens have their nests in a variety of ways, but they are much smaller than those of ants and migrate frequently.

The fight against leaf-cutting ants is based on the use of granulated bait that can be applied locally, when nests are found, or systematically, homogeneously distributing an amount of bait in the area. There are different commercial brands of granulated baits on the market, and there are basically two presentation modes, which are: in bulk and packaged in sachets 5 or 10 grams. For the control of a nest of Scorchbills, only 5 grams of granulated bait applied to the side of one of the foraging trails is needed.

Before placing the bait, it must be observed if the trail is foraging, as it is possible that one or more trails are being used to transport only cisco for covering the nests. In the case of quequens that make their nests with loose soil and Acromyrmex niger, 5 grams per track apply. If the activities to combat leaf-cutting ants are carried out in a localized manner, aiming only at controlling the ants' nests, effectiveness may not be achieved due to the infestation of quequens, which have nests that are difficult to locate and will always be in a density greater than that of ants.

That is why the systematic application of ant baits in the pre-planting period is often crucial for the successful implementation of a forest plantation, but it is important that this activity takes place between 15 and 30 days before planting. If carried out over a period of more than 30 days, migration of quequens nests may occur in the area to be planted. The implantation of a eucalyptus forest in a pasture area requires more attention with leaf-cutting ants, since, even in the absence of ants, you can have an attack of quequens in up to 70% of the seedlings in the first 30 days of planting.

However, the damage caused by quequens in eucalyptus is restricted to the first months after planting. From six months onwards, there is no longer a need to fight ants in places where only quequens occur, contrary to what is recommended in plantations where ants occur, which need to be monitored and controlled throughout the cycle forestry.

In pine plantations, there is a situation in which there is no need to carry out systematic control in the pre-planting period: in areas of reform, whose previous planting was pine not thinned, with fallow between the shallow cut and new planting of less than six months, planting taking place in winter, in places far from areas of native forests (Permanent Preservation Areas, Legal Reserves, etc.) and when the occurrence is only of quequens.

In addition, the influence of weed management on quenquén attacks was observed, and where this management is carried out by means of mowing, there are less ant attacks on plants of commercial interest, since mowing does not completely eliminate weeds, which end up serving as resources for the ants to forage, and, in this case, combat can only be carried out in the first year after planting.

When herbicides are used, it is necessary to manage ants, at least while weeds are being managed (until the third or fourth year after planting). Quenquens do not cause damage to adult pine plantations, so it is not necessary to monitor and control quequens at this stage. All the factors that influence the management of leaf-cutting ants in eucalyptus and pine plantations are contained in an electronic spreadsheet (Computer tool, Ant Management) available on the Embrapa Florestas website. This tool contains 16 different recommendations depending on each situation, aiming to guide decision-making on the proper handling of leaf-cutting ants at each stage of planting.