Beer waste as a pesticide?

Some pesticides can be harmful to humans, but beer may be an organic solution to that problem, suggests a study published in Frontiers in Sustainable Food Systems.

A team of researchers, led by Maite Gandariasbeitia from NEIKER-BRTA Basque Institute for Agricultural Research and Development in Spain, has investigated organic by-products of used beer grains (called bagasse) and canola (rapeseed oil) cakes, to find that they make a useful pesticide when mixed with cow manure.

“Rapeseed cake and beer bagasse are two potential organic treatments which have shown really positive results in previous studies,” says Gandariasbeitia.

“Their high nitrogen content promotes the activity of beneficial microorganisms in the soil, which helps to break down organic matter like manure and kill off nematodes and other parasites which damage crops.”

Lettuce roots. There are big welts on the roots. Behind the roots are more lettuces
Root galling caused by root-knot nematode infestation. Credit: Maite Gandariasbeitia et al

Nematodes are a common crop-destroying pest, because they break into plant roots and lay their eggs there, causing big swellings – called galls – to develop.

“This damage negatively impacts root development and means the crop can’t take up nutrients efficiently, slowing plant growth and ultimately leading to reduced yields for farmers,” explains Gandariasbeitia.

After using the beer-poo pesticide on lettuce crops, the researchers saw a significant reduction in root galls, and a 15% increase in yield after one year. They also found more useful microorganisms in the soil after treatment.

“There are still many questions to answer so that we can gain a better understanding of what happens in the soil during and after these bio-disinfestation treatments,” says Gandariasbeitia.

“This can help us to really elucidate what characteristics we should be looking for in other potential organic treatments to be effective in tackling soil parasite populations.”

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