Wild flowers increase the presence of beneficial organisms

Among the most used are: chamomile, calendula, Swiss chard and arugula. They all contribute to an agriculture with more biodiversity.

03/06/2022

Crop pest control has changed a lot over time. In the past, the only objective was to eliminate the "problem", regardless of the consequences that this action could have on the rest of the ecosystem. For some years, and fortunately, this perception has changed radically and more and more, biological organisms are used for crop protection.

The story tells that, Charles Valentine Riley It was the first to use beneficial insects to control a population of "ribbed mealybug" considered a pest insect back in 1888, but it was not until the mid-50s that this practice began to be used commercially.

It is true that the practice of agriculture goes in the opposite direction to the increase in biodiversity, whether plant or animal. For this reason, it is of vital importance to try to maintain a "minimum" of spaces destined to maintain this diversity on farms.

To name some of these large-scale projects, we can highlight the program of Operation Pollinator developed by the multinational Syngenta and whose objective is to demonstrate to the world that increasing the number of beneficial insects on farms is possible with the implementation of just one 5% of the agricultural area with floral margins adapted to each area.

The interesting study has been carried out for more than three years in various agricultural plots in Spain and Portugal and is based on the establishment of specific habitats for beneficial insects such as pollinators, predators and parasitoids.

Another interesting contribution in the sense of increasing biodiversity, are the various research programs that are being carried out by the IRTA, University of Lleida (UdL) and Autonomous University of Barcelona (UAB) in different areas of Spain, where they managed to identify those plants with a certain ability to attract beneficial organisms.

In the case of the gray apple aphid (Step Dysaphis plantaginea.), hoverflies and parasitoids are the best allies because the adults feed on pollen and nectar, and the larvae are the ones that carry out the biological control action.

In the study, they initially tried to enrich the margins, the area where the crop maintenance machinery does not pass, with marigolds y cruciferous, but the effect was not enough. For this reason, they are testing the effectiveness of inserting floral bands with the crops, without this preventing the normal passage of the machinery for the necessary tasks. In the fall, they sowed a mixture of seeds from calendula, argula, chamomile, egg, clover y chard. One of the challenges is to get the plants to grow well and establish themselves in order to check their attraction effect.

Application in greenhouses

In protected crops, interesting projects are also being carried out, mainly in the cultivation of tomato and lettuce. "Horticultural crops are very dynamic and cycles are very short, so the existence of margins of selected plants help us to have natural enemies prepared on the plot before the plague arrives," he says. Judit Arno, researcher of the IRTA sustainable plant protection program.

The primary function of plant margins is to provide shelter to predators at the time of the year when there is no crop, or when the tomato is already in the greenhouse, but the whitefly or aphids have not yet arrived, thus achieving a bridge effect between crops.

The variety of beneficial organisms is directly related to the greater number of host plants, and that is why it is important to know the tastes or preferences of the insects as well as the cycles of the plants (hosts and crops).

In the case of tomato cultivation, a good functioning of the mirids as predators was observed, which like to live in the marigolds, and in the case of the aphid on lettuce, the hoverflies, which prefer the sea alder. “Mirids are generalist insects that eat many tomato pests such as whiteflies, aphids, tomato moth eggs or red spiders. The fact that they have several prey guarantees that, if they fail to find one, they will continue to stay on the margins feeding on other insects," he adds. Arno.

Floral bands, other benefits

Studies confirm that floral bands can also help alleviate the problems caused by voles, who instead of feeding directly on the roots of fruit trees, find another attraction in the peripheral plantsAt the same time as these, they favor the presence of their predators, such as birds of prey, reptiles or small mammals such as the European polecat, a species in danger of extinction. "Instead of eliminating the vole, we offer it the roots of the floral bands so that it continues to have food and does not affect fruit production, while favoring the presence of its predators," he explains. Jordi Cabrefiga, researcher of the IRTA sustainable plant protection program.