Author Roman Rachkov, "Klimatika"
Warmer winters and longer growing seasons are changing the conditions under which a number of agricultural pests develop. For farmers, this means a new challenge: how to protect their crops without increasing their dependence on chemical plant protection products. One of the possibilities comes from a seemingly simple source: things we know from the kitchen and garden. European legislation defines them as “basic substances“, and nettle extract is among the approved ones. What is its strength, and when is its use allowed?
Climate change is changing pest control
When the climate changes, most pests multiply more aggressively because mild winters kill fewer of them and summers are longer. Farmers respond to this with more chemical pesticides, which are produced from fossil fuels. Almost all agricultural chemicals are like this, and their production releases greenhouse gases. In this vicious circle, the climate changes the conditions for the development and spread of certain pests. The use of synthetic pesticides partially solves the problem, but in turn this also has a carbon footprint.
There is also a hidden problem: healthy soil is full of beneficial bacteria and fungi and works as an absorbent, absorbing and retaining carbon dioxide (CO₂) from the atmosphere. Aggressive chemicals kill these organisms and the soil loses its ability to “keep” carbon, even starts to release it itself.
A solution from the garden
The European Union has introduced an interesting category of substances called “basic substances” (Article 23 of Regulation (EC) No 1107/2009). These are products whose primary purpose is not to combat pests, they are food and household products that science has proven to be effective against fungal diseases in plants. They are also good at fighting insects and have stimulating properties. These include baking soda, whey, sunflower oil, vinegar, and beer.
What can nettle extract do?
The most accurate example in this case is the water extract of nettle, officially approved by the EU in 2017. Folk medicine has used it for centuries as a "nurse", and in our time it is a completely legitimate and regulated product with three main functions.
The extract is approved for use against aphids, mites, and other pests, as well as against some fungal diseases in specific crops.
Nettle acts against specific pests listed in the official tables of use. These are aphids (e.g. Myzus persicae, Aphis fabae, Macrosiphum rosae), ground fleas, apple and pear fruitworms, and mites in certain crops. It is these species that are "thriving" as a result of increasingly mild winters, and nettle is becoming an important tool for managing the effects of climate change.
The approved use against fungal diseases is for alternaria on cabbage crops, oidium and alternaria on cucumber, moniliosis on fruit trees, mildew on vines, and phytophthora on potatoes.
Dried nettle can be mixed into mulch as a stimulant when growing tomatoes and cucumbers. This is a separate use and should not be confused with spraying on the leaves.
How to prepare and use the extract
Soak young shoots and leaves in drinking water: 75 g/L fresh nettle or 15 g/L dry, stirring daily and leaving for 3-4 days at about 20 °C. Then it is strained and the filtrate is diluted 1:5.
The applications are with a typical dose of 1500 g/hL dry material, every 7-15 days according to use, with a quarantine period of 7 days before harvest.
Two common mistakes worth mentioning: nettle does not act prophylactically against aphids, it is sprayed only when the pest is already present. The EU approval is not comprehensive, for each use outside the explicitly described crops, doses and methods a separate assessment at European level is required.
What is the climate benefit?
The use of nettle creates fewer emissions. While the synthetic pesticide goes through fossil fuel extraction, an energy-intensive chemical factory and thousands of kilometers of transport. Nettle grows in one place, and its extract is only water and requires some time. The difference in the ecological footprint is clearly significant.
The soil remains a “sponge” for carbon dioxide. Without aggressive chemistry, the microbiome in it survives, and the soil, rich in organic matter, continues to capture carbon. In general, the use of more sparing means can be a step towards the transition to agriculture with a lower resource and carbon footprint.
Crops become more resistant because nettle stimulates the plants' own defenses. This results in thicker foliage that is better protected against drought and temperature shocks.
An important clarification is that this solution is not so straightforward, because nettle does not have a long-lasting effect and therefore treatments must be frequent (7-15 days). This means more work with machinery in the field, energy must be saved by combining with other practices. The doses are precise and different for each use, and many farmers simply do not have access to proven protocols for large areas.
The correct approach is probably in the so-called Integrated Pest Management (IPM): Basic substances are a powerful tool in the kit, but they are not a substitute for everything else.
About the abundance of nettle in Bulgaria
Bulgaria has natural advantages, because nettle in our country grows abundantly and wildly throughout the country: along rivers, fences and in the fields. The raw material is literally “one step away”. We also have a strong, living tradition in herbal medicine with this plant, so its use in agriculture will probably also be much easier to accept and practice compared to a completely new technology.
From a regulatory point of view, supervision in our country is entrusted to the Bulgarian Food Safety Agency (BFSA). For the uses of the basic substances approved in the EU, a separate registration is not required in our country, but the same conditions apply: crops, doses, deadlines and quarantine period, and the documentation attached in the sources (Revision 3.0) is a technical reference, not an independent permit from the BFSA.
Can the farmer prepare nettle extract himself?
Yes. In an official response to the author of the article from this year, the BFSA confirms that nettle is approved in the EU as a basic substance and for products containing only such a substance, a separate permit for use is not required.
This means that farmers can prepare and use an aqueous nettle extract themselves, without purchasing a registered product from an agropharmacy, as long as they comply with the approved applications, crops, doses and deadlines.
Legal basis: Implementing Regulation (EU) 2017/419 and Art. 28 of Regulation (EC) No. 1107/2009.
For small and medium-sized farms in our country – with tomato beds, vineyards and orchards, nettle is an easily applicable tool. For large industrial farms, the transition requires more planning in the frequency of treatment and the logistics of the raw material.
A wild plant that costs zero leva, grows along every road and protects our tomatoes from aphids – sounds too good to be true…And yet this is a regulated reality with official EU approval, precisely described recipes, verified doses and a quarantine period.
But nettle extract is not a miracle cure, but requires frequent application, precision and patience. It will not replace the chemical industry entirely, nor will it save the planet alone, but it is not to be underestimated. The right place for basic substances is in Integrated Pest Management as a more gentle tool in the whole package.
The example with the nettle shows that some of the solutions for more sustainable agriculture do not always require new and complex technologies. Sometimes they rely on long-known practices, but we now also have clear rules about when, how and against which pests they can be used.