The most harmful leaf-cutting ants are classified into two genera: Atta and Acromyrex, which until the early 1980s were present only in the north of our country (provinces of Formosa, Misiones, and Corrientes). With climate change, the lack of cold generated an expansion of their range of action and they are already colonizing regions in the center of the country, including the cities of Buenos Aires, Rosario, and Córdoba capital.
It is a pest with nocturnal and morning habits that, in a single day, can defoliate half of the foliage of a wide variety of herbaceous plants, fruit trees, ornamentals, and horticultural plants. Cutter ants can cause severe damage to plants, in this case, a hydrangea. Garden Magazine Archive
Like the generality of ants, they live in organized colonies and with defined social castes (expeditionary, workers, soldiers, queen, nannies, males), they present polymorphism and division of labor.
Millions of years ago, they evolved from the lands bordering the east coast of South America and have co-evolved with their natural environment. They are among the best-adapted and successful insects. They are among the five most important pests in seven South American countries, attacking a wide variety of vegetation, especially areas of crops and rural grasslands, and parks and gardens in urban environments. While in the north of the country, there are cutter ants that look red, in the metropolitan area of Buenos Aires (AMBA), the majority of cutter ants are black and the red ones are usually the so-called butcher ants, which are beneficial for the plants. Pixabay
Secrets of the nest
From November to April, the ants reinforce the entrances to their nests with sticks, and the carrying of leaves goes from greatest to least, tending to decrease in March, the time in which the reproductives (virgin queens and males) get ready for the nuptial flight… This occurs in the first rains at the end of summer or early fall. Once the queen is fertilized, they begin to form new nests by burying themselves about 25 cm into the ground. During the fall until the arrival of the winter cold, the transport of leaves into the nests intensifies.
They do not necessarily select the nearby plants to defoliate and use this vegetative material in the development of the fungus on which the pupae will feed – the stage after the larva – but rather they first choose the furthest plants. This is a strategy that will allow them to conserve food resources by avoiding overexploitation of nearby plants and, on the other hand, keep their nest hidden from their natural predators.
Fruits, flowers, leaves, and other fresh plant parts are taken into the nest to be degraded before being introduced into the underground labyrinths where the fungi grow. The workers lick and cut plant parts into pieces one millimeter in diameter, then chew the fragments until they look like porridge: this mass is deposited where the fungi are, which are covered with fungal mycelia. Then, they add fecal material on top of the mycelium, creating a nutritional status that causes the mushrooms to grow rapidly. Once grown, they are collected by the nanny and gardener ants to feed the colony.
How to fight ants
Chemical control consists of the use of antacids-based toxic baits (a granular insecticide coated with an attractive sugary substance). The baits are placed, with gloves, near the paths left by the ants, so that they are taken to the anthill where they will release the active ingredient (sulfonamide). If the anthill is located (which is sometimes difficult), bait can be applied directly. liquid antacid inside it.
It is important not to confuse the anthill, those of cutter ants are always underground, while those of butcher ants (generally red, harmless, and even beneficial for our plants) are mounds above ground level.
The use of agrochemicals can be replaced by a non-chemical control, based on organic toxic baits, made with broken rice, powdered orange juice, and copper sulfate. The orange aroma is attractive to ants, which will take the grains to the anthill. Then, the low oxygen and high-temperature conditions of the anthill generate – through fermentation – alcohol, which kills the fungi that grow inside and, therefore, deprives the colony of food.
On the other hand, if you find the mouth of the anthill, make a semi-liquid paste with yeast and sugar, to pour inside. The yeasts will compete with the fungi that live in the anthill for space and will take away food from the colony.
evolved insects
It is admirable how they evolved, to the point of being able to communicate. For example, expeditionary ants, upon finding an acceptable food source, return to the nest and recruit groups of workers through hormonal signals, emanating a hormone (methyl 1-4-methyl pyrrole 2 carboxylase) that leads them to the place where the nest is located. food source (chemical communication).
The antennae are capable of perceiving odors and flavors, in this way, they can discriminate individuals that are not members of their colonies or strangers. They smell the smell of humans, so you should never touch the products that we will use to control them with your hands.
In addition, they secrete a pheromone specific to each colony and are capable of returning to their nest following the scent trail left by small droplets of a substance secreted from the end of the abdomen.
