A group of researchers from the UBA Faculty of Agronomy (FAUBA) studies the effect of substances extracted from common plants such as garlic (Allium sativum) and palo amargo (Picrasma crenata) to develop biological insecticides and, eventually, combine them with chemical products to control pests in stored grains and seeds.
“From the plant-insect relationship we study the most effective ways to attack the different pests of stored grains. Some of the insects we work with are the rice weevil (Sitophilus oryzae), the flour weevil (Tribolium sp.), The toothed grain beetle (Oryzaephilus surinamensis) and the grain borer (Rhyzopertha dominica), among others, considered harmful because they attack seeds, grains and milling products such as flours ”, affirmed Silvia Rodríguez, professor and researcher at the Department of Agricultural Zoology at FAUBA.
“We study the effects of some secondary metabolites, which are those substances produced by plants, particular to some species, which do not have a direct role in their growth or reproduction but can act as defenses, being fundamental in the insect-relationship. crops. We are focusing on the best ways to extract and apply them to evaluate their impact on different pests, ”explained Rodríguez.
While good results were achieved in the laboratory, the researchers noted that further field testing is necessary. “Today we are participating in many works and conferences, but to produce these bioinsecticides there are protocols that must be followed and we are halfway there. Each pest and crop has its peculiarities, so we must continue investigating ”, explained the FAUBA teacher, who also works in the School of Grain Classification Experts.
A difficult cocktail to digest
Some of the main lines of research of the Department of Agricultural Zoology at FAUBA focused on the study of palo amargo for pest control. In this regard, we worked with the researcher Hermann Niemeyer, from the Faculty of Sciences of the University of Chile, who has a long history in the analysis of secondary metabolites: “We began to investigate the dynamics of hydroxamic acid in different cereals. For example, we saw that in the early stages of crop development, the acid was more concentrated and then it was diluted, with which the plant was more exposed to aphids attack ”, Rodríguez introduced.
“We also observed that barley had a lower concentration of this acid. A wide range of aphids or aphids attack cereals in all their cycles. Sometimes, when changing the growth stage of the plant, the species of aphid that affects it also changes. This would open a very wide range of studies, "he added.
The palo amargo was one of the alternatives that FAUBA analyzed to control pests of stored grains. To do this, Rodríguez completed his doctoral thesis at the University of La Plata and then obtained the extracts at the Faculty of Pharmacy and Biochemistry of the UBA. From these studies, metabolites were extracted with different solvents: "Currently we work with a type of partition extraction, although we go through other methods because the extraction process varies the effects obtained," he explained.
The palo amargo gave positive results on the aphids Aphis nerii and Myzus persicae and on the thrips Gynaikothris ficorum and Caliothrips phaseoli through ingestion but not on the ants (Acromyrmex lundi): “A flipping effect was observed. In the first three hours of application, the insect vanishes, although later it is revived ", explained the researcher, and explained that with this turning effect the effectiveness of the conventional insecticide can be increased and the same level of efficiency could be achieved with a lower level of enforcement.
More ongoing research
FAUBA research continues to advance with the analysis of new treatments for pests: “In addition to palo amargo we also work with garlic, which, despite being studied, there is much more to prove from the way of extraction and the insects to control. The metabolites are many and can act together and even synergistically ”.
Likewise, the chair studies other plants such as eucalyptus (Eucalyptus globulus) to generate products such as essences, with interesting results. Other trees are also used for research: “We worked with the extract of paradise (Melia azedarach), which has a high degree of effectiveness against pests. However, the fruit of paradise is the well-known poison, toxic even to people, so it must be handled with caution and requires research, since not everything that is said biological is good. Another similar extract is that of neem (Azadirachta indica) which, like paradise, in low concentrations can also be dangerous for humans ”, highlighted Rodríguez.