• homepage
  • Crop soil
    • Essential laboratory tests
    • Soil texture and structure
    • Clay-humus complexes and cation exchange capacity
    • Other interesting data that can be included in a laboratory analysis - limitations of laboratory analyses
    • Soil acidity and alkalinity
    • Humus; formation and evolution
    • Soil fertility; is the apocalypse coming?
    • The microbial world and soil fertility
    • Rhizosphere, mycorrhizae and suppressive soils
    • Correction of a very clayey or too calcareous or too sandy soil
    • Estimation of humus loss
    • Compost production for a vegetable garden
    • The different phases of composting with a thermophilic phase
    • Weed management in the vegetable garden
    • Ploughing or no-ploughing?
    • The rotovator, the spade-fork and the grelinette
  • Fertilization
    • Synthetic or organic fertilizers?
    • The reasoning behind fertilisation in the vegetable garden
    • Examples of rational fertilisation for some vegetable plants
    • The problem of nitrogen assimilation in organic farming
    • Can vegetables be forced to grow?
    • Brief description of some mineral fertilizers
    • Tools for measuring nitrates
    • It is easy to cheat in organic farming
  • Biocontrol
    • Integrated Biological Crop Protection; first approach
    • Agroecology and ecosystem services in agriculture.
    • Vegetable garden and biodiversity areas
    • Permaculture; an example of pseudoscience in agriculture
    • Mandatory control of regulated pests
    • Anti-insect nets
    • Imports of beneficial auxiliaries
    • against aphids
    • Against whiteflies and scale insects
    • Against beetles, wireworms, cutworms, cortilian beetles, tipulas, ants
    • Against mites, trips, bedbugs
    • Crop rotation
    • Varietal choice
    • Solarisation and false sowing
    • Biocontrol plant protection products
    • Biostimulants
    • Other methods to reduce the risk of disease
  • Treatments
    • Organic or conventional treatments against pests
    • Some remarks on pesticides registered in organic farming
    • Copper and sulphur compounds
    • Pyrethrins
    • oil of neem and spinosade
    • The virtues of nettle manure under the magnifying glass
  • More

Introduction to integrated methods in the vegetable garden

The virtues of nettle manure under the microscope

Chapter : Treatments

Previous or next articles ; click on a title to go to the page

- Organic or conventional treatments against pests.

- Some remarks on pesticides registered in organic farming.

- Copper and sulphur based compounds.

- Pyrethrins.

- Neem oil and spinosad.

⇒ The virtues of nettle manure under the microscope.

Nettle manure, used by our grandparents when pesticides did not exist, is back in fashion. Its scent is supposed to deceive pests, a grail that our grandparents would have underestimated when they discovered the usefulness of pesticides.

Nettle manure is part of a list of products known as "Natural Preparations of Little Concern". These products are said to have no phytopharmaceutical action, but to have bio-stimulant properties. In July 2014, these preparations were the subject of a simplified approval regime for their use and marketing following the action of several associations. An annex to the order of 30 April 2016 establishes a list of plants (1) including chamomile, mint, lemongrass, clove, tarragon, nettle ... which "may be sold by persons other than pharmacists"; a godsend for all those who wish to exploit this economic niche. As for their real effectiveness! Where are the serious scientific studies validating their properties in agriculture? If these products are really effective, why don't farmers use them when they have been known for a long time, rather than investing in very expensive phytosanitary products?

In organic farming, nettle manure is often recommended to prevent all kinds of pest invasions on both vegetable crops and fruit trees. It is a repellent that avoids the use of synthetic pesticides.

I have sometimes used nettle in the form of a decoction or herbal tea. The results were always disappointing. One of these trials ended with a surprising finding. A trial of nettle manure on shallots to prevent the onion maggot did not have the desired effect. However, I was surprised to find adult aphids on some of the shallots a few days later, which were not present before the nettle manure treatment. The possible reasons for this aphid invasion are simple to understand. Either the nettle manure is unable to keep out an already established pest that I would not have noticed, or it attracts them. Like all other plants, nettles are victims of polyphagous pests, including the shallot aphid, which I did not know at the time (2). It is strange to claim that nettle manure can keep pests away when in nature, nettles attract them!

The shallot aphid can indeed find other hosts when it does not find its favourite food like other nettle pests: this is the case of the Arctia caja caterpillar (Scalille Martre) which is fond of nettles and is known to cause damage in vegetable gardens. If you grow sorrel, you should know that it can be attacked by the amptogramma bilineata (golden brocatella), a butterfly that also likes nettles. Several species of common wireworms that are regularly found as adults on nettle foliage are polyphagous and are often harmful to crops (2).

As far as I know, there is no scientific study that has established that the attractive powers of nettle towards all these pests would have disappeared after maceration in water to produce a slurry that would have an opposite effect. However, pests have a keen sense of how to find their hosts from substances emitted by them in very small quantities.

So if you think it is worth signing a contract with the devil to cure your plants, use nettle manure.

Nettle manure is also known to fortify plants and strengthen their natural defences, as it contains a lot of nitrates. It is a kind of foliar fertiliser. But this is also true of all highly fermentable, nitrogen-rich plant products that can be macerated in the same way, such as lawn clippings.

1)https://www.legifrance.gouv.fr/affichTexte.do;jsessionid=F061E8A49442AB60CB6C51116A140B4F.tpdila20v_2?cidTexte=JORFTEXT000032472055&dateTexte=&oldAction=rechJO&categorieLien=id&idJO=JORFCONT000032471555
2) L’entomofaune des orties – Hervé Guyot -Insectes 3 n°158 - 2010

launch facebook
launch twitter
launch linkedin
launch pinterest
launch snapchat
launch instagram

Specify a search word ⇒

The search will be conducted in all chapters and articles