Natural insecticides with native plants

Natural insecticides with native plants

Argentine scientists found active insecticidal compounds in native plants such as the shadow of the bull, the santa rosa and the yerba lucera. They tested its efficacy against pests such as the fall armyworm in the laboratory.

The research has several advantages, among which is the possibility of growing large-scale crops like organic corn, cotton and soybeans organically, without agrochemicals, an aspect highly valued in grain export markets.

Corn is one of the most cultivated cereals in the world; it ranks third after rice and wheat. Furthermore, Argentina ranks highly in the production of grain, after the United States, China, the European Union, Brazil and Mexico. Taking into account that this year the tax on corn exports was eliminated and that the cultivated hectares are in permanent extension, it becomes strategic to combat the pests that damage this grain.

Researchers from Tucumán from the Institute of Organic Chemistry of the Faculty of Biochemistry, Chemistry and Pharmacy (FBQF) of the National University of Tucumán (UNT) study insecticidal properties in native plants of Argentina and Bolivia. From the use of pure compounds extracted from plants such as the holy rose, the shadow of the bull and the yerba lucera, they found that they kill or drive away the larvae of the fall armyworm, a pest that affects both this crop as well as soybeans and the cotton one. In addition, the team demonstrated the insecticidal activity of these compounds on the fruit fly, another pest that affects citrus, peach and guava crops.

Among the plants analyzed, the so-called bull's shadow owes its name to the fact that it shelters cattle in times when other tree species lose their foliage. Medicinal properties are attributed to it as an antimicrobial and, at the end of the 19th century, it was used for dysentery and digestive problems, such as constipation. For its part, yerba lucera has also been used to facilitate the action of the intestine, the liver, as a digestive and against indigestion.

The team is made up of Alicia Bardón (director of the investigation and current rector of the UNT), Susana Borkosky, Nancy Vera, Elena Cartagena, Mario Arena and Adriana Neske. The research results were published in prestigious scientific journals such as "Journal of Chemical Ecology", "Journal of Pest Sciences" and, more recently, in "Neotropical Entomology".

The researchers maintain that the main work they carry out consists of isolating bioactive natural products, to test different biological actions. "The plant is like a large laboratory and finding beneficial properties in some of its molecules is a fundamental part of our task", synthesizes Borkosky.

The research is in an experimental state, meaning that although the results are successful in the laboratory, they are not yet applied in the field or on a large scale. The challenge of the group is to verify that not only the pure molecules have an insecticidal effect, but that as a whole they are enhanced in the extract, which would result in a greater amount of bioactive product, that is, of bioinsecticide. So far they have tested around 40 plant extracts and obtained insecticidal effects of different degrees (mild, moderate and very effective).

Vera specified that the future objective is to do field tests with the most active extracts that are achieved and observe the effect, because in uncontrolled situations, that is, outside the laboratory, other factors such as light, rain, soil influence , etc. "We are looking for models of potential insecticide molecules, so that their synthesis can then be developed or their activity improved, perhaps in collaboration with other laboratories," the specialist told Argentina Investiga.

Borkosky announced that one of the team's objectives is to patent extracts or pure compounds with insecticidal effect, but clarified that the limitation today is the minimum amount of pure compound that they manage to isolate from plant material. "We need the plant to be arable, to be able to grow under controlled conditions on a large scale and to be profitable to manufacture," he reflected.

The benefit of producing organic grains

One of the great advantages that this research entails is the possibility of producing organic corn, cotton and soybeans, that is, without agrochemicals (pesticides or synthetic fertilizers) or added hormones. This gives an advantage when exporting, because some international markets require organic products or prefer them over others. Borkosky commented that the insecticides they study, being of natural origin "are less polluting and have less impact on other organisms and on the soil, because they degrade more easily."

The laboratory work is carried out with the collaboration of the Obispo Colombres Agroindustrial Experimental Station (EEAOC), an organization that provides larvae, fruit flies and prepared cultures to carry out the laboratory tests. Analía Salvatore, from the EEAOC Agricultural Zoology, considered that the scientists from Tucumán "found valuable formulas that must be disseminated, we test them and they work." He added that "the benefits are many because for organic agriculture it is imperative to have natural insecticides."

The most important pest of corn

The fall armyworm is the larva of the moth or night butterfly, whose scientific name is "Spodoptera frugiperda", which mainly attacks corn, sorghum and rice, but also, to a lesser extent, soybeans, vegetables and cotton, among other crops. This pest, considered the most important of corn, is distributed throughout the Western Hemisphere, from Southeast Canada to Chile and Argentina.

The fall armyworm goes through different stages during its life: egg, larva or worm (it is the stage in which it damages crops because it needs to eat in quantities), pupa and adult or butterfly. The larvae, in general, are dark with three narrow longitudinal pale stripes and can measure from 3 millimeters in their initial stage to 35 millimeters in their last stage.

The fall armyworm makes scratches on the tender parts of the leaves, which later appear as small translucent areas. Once the larva reaches a certain development, it begins to eat foliage perfectly in the bud (inner and tender part of the plant). When unfolded, the leaves show a regular row of perforations through the lamina or elongated areas eaten.

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