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Date: Mar 17, 2021

Pheromones, mulch and wildflowers – how to control pests without pesticides The EU-funded WIDE-Synergies project will consider the main three pests in crop farming – weeds, insect herbivores and pathogens – together.

Most crops require pesticides to grow profitably. But many pesticides are too efficient at killing insects, often indiscriminately. They aim to hit specific crop pests but spray deadly fire at friendly insects and some may harm pollinators such as bees. While the plight of bees attracts attention, other less visible insects are also in peril. Recent research found that 40% of all insects are declining, and a quarter could be wiped out within a decade.

Predators

Predators such as ladybirds can help keep down the population of pests such as aphids on wheat (© Picture: Severin Hatt, University of Bonn)

 

This is not inevitable. We can cut down on the use of many insecticides. To this end, scientists work on ways to protect crops from insect pests without wiping out beneficial insects which are often crucial to healthy ecosystems and provide sustenance to birds and other wildlife.

One strategy is to disrupt the mating of insects by jamming their chemical signals. Insects such as moths waft pheromones into the air, which allows males to follow the perfumed path to a female. The concoctions are usually specific to a species of insect.

By making the same pheromones as the insects and releasing them over crop fields, it is possible to confuse the insects by hiding their pheromone trails and making it difficult for them to pair up. This technique is called mating disruption. The synthetic pheromones must be the same as those made by the insects, and unfortunately manufacturing them chemically is costly. As a result, mating disruption is mostly for high value fruits and vegetables, such as tomatoes, apples and pears. But now a European project called Olefine has developed a way to manufacture pheromones using yeast fermentation, making them a more affordable alternative to pesticides. This is done by introducing genes for insect enzymes into yeast [...]

In Germany, Dr. Severin Hatt in the agroecology and organic farming group at the University of Bonn is sowing crops without agrichemicals in ways that he hopes will supress diseases, insect pests and weeds, as part of a project called WIDE-synergies.

He planted seeds at the experimental farming station outside Bonn to grow different combinations of winter wheat and winter broad beans. There are 32 strips of crop, each measuring 25 metres long and 9 metres wide, in eight different planting regimes. The idea is to compare the effect of techniques such as intercropping, living mulch and wildflowers with strips consisting of wheat or broad bean.

Pests and disease often are specific to one crop. Planting this one crop in a field makes it easy for a pest or disease to spread from one plant to the next, which is why agrichemicals are often so necessary in monocultures. Mixing two crops such as wheat and broad beans together – called intercropping – makes it less straightforward for a disease or pest to spread from plant to plant.

Another strategy is to sow a living mulch amongst wheat. ‘These are grasses and legumes that cover the soil,’ explained Dr. Hatt. ‘It is an ecologically friendly way to reduce weeds.’ The living mulch will not compete against the crop but against weeds that try to grow there.

Dr. Hatt will also plant wildflowers beside some crop strips to see if this encourages beneficial insects, in the hope that they will transfer to nearby crops. The wildflower strips will consist of a mix of a dozen flowers that will attract beneficial insects, including predators of crop pests such as aphids. ‘We will then monitor the predators of aphids, particularly ladybirds, hoverflies and lacewings, and some parasitic wasps,’ said Dr. Hatt. He will check regularly to see how many aphids are in a crop strip and if there are more natural enemies of these pests in some situations than in others.

 

... read the whole article:

  horizon-magazine.eu | 17.03.2021

 

... project page:

  www.aol.uni-bonn.de

WIDE Synergies

 

... more on this topic:

  phys.org | 17.03.2021

  www.agroportal.pt | 16.03.2021

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