Protecting Market Garden Crops with Plant Extracts

Organic matter autonomy in market gardening Soil regeneration NBSOIL

A plant extract refers to a solution obtained by immersing a plant in a solvent (water, alcohol) or by distillation so that the plant releases the mineral elements and complex molecules it contains.

Plant extracts can be prepared on the farm. There are also formulated products on the agricultural market derived from plant extracts: essential oils, insecticides, or foliar fertilizers.

Plant extracts have been used for millennia in agriculture. The development of biodynamic agriculture and the search for alternatives to phytosanitary products mark a significant renewed interest in these products.

Plant extracts show various benefits in their use:

Reduction of doses of copper and sulfur in the fight against downy mildew and powdery mildew
Reduction of insecticides in the fight against pests
Foliar Fertilization in the prevention of deficiencies

This article aims to synthesize existing documents on the use of plant extracts. The modes of action of plant extracts are still little known and understood; the recipes presented here have therefore only been established following field observations and currently have no scientific value.

Modes of action

The application of plant extracts allows acting on plants through various modes of action, direct and indirect:

Creation of an unfavorable climate for the development of diseases and pathogens
Reduction of overoxidation and overvoltage phenomena appearing in the plant during stress and various pollutions (notably pesticides)

Stimulation of the natural defenses of plants (preventive action)
Direct fight against pathogens by a repellent or even biocidal action (curative action)

What processes are available?

Success conditions for a plant extract

To maximize the effectiveness of preparations, it is necessary to have a global and complementary approach to their use. For this, it is essential to first know their effects well and position the right preparation at the right time:

Favor rainwater
Plant harvesting is done at different times of the day depending on the organs used in the preparation. In the morning and spring, active ingredients are concentrated in the leaves, flowers, and stem. In the evening and autumn, active ingredients are concentrated in the roots.
pH of water between 6 and 6.5
Prefer a stainless steel or copper cauldron and use a lid
Control boiling
Preferably apply preparations after rain or watering at the base of crops
Favor morning application of plant extracts for foliar spraying
Favor evening application of plant extracts for soil watering
Adapt extracts to your plots and the year's climate
Beware of mixing plant extracts:
- Avoid mixing more than 2 plants at a time
- Avoid mixing several decoctions, essential oils, and manures
- Alternate plants

Herbal teas and infusions

Benefits

Hinders the development of diseases and pests

Instructions

Once the plants of interest are chosen, the steps for making herbal teas and infusions are as follows:

Cut the plants into coarse fragments
Immerse the plant fragments in cold water
Heat
Turn off the heat when the water starts to simmer (from 80°C for willow, meadowsweet, nettle, horsetail, elderberry, and valerian whose active ingredient, acid salicylic acid, is destroyed above this temperature, 90°C for other plants)
Cover and let infuse until cooled (infusion must last at least 20 min)
Dynamize or stir for 20 min
Filter

Once all these steps are completed, the herbal tea is ready for use.

Doses per hectare:

100 to 150 grams of dry plants in 5L of water / ha

or

800 to 1000g of fresh plants in 5L of water / ha

This preparation can be stored for a few days in the fridge or several months if bottled hot and kept cool and away from light.

Decoctions, instructions

Benefits

Strengthens plants
Hinders the development of diseases and pests

Instructions

Once the plants of interest are chosen, the steps for making decoctions are as follows:

Cut the plants into coarse fragments
Let soak for 24h in water
Heat and maintain boiling for 20 to 30 min at a very low boil (90 to 100°C) and under a lid, to avoid losing vapors rich in essence
Let cool without removing the lid
Filter
Dilute to 10% and spray

Once all these steps are completed, the decoction is ready for use.

Doses per hectare:

100 to 150 grams of dry plants in 5L of water / ha

or

800 to 1000g of fresh plants in 5L of water / ha

This preparation can be stored for a few days in the fridge or several months if bottled hot and kept cool and away from light.

Manures and fermented extracts

Benefits

Strengthens and stimulates plant growth

Instructions

Cut plants into fragments
Fill a container 3/4 full with whole plants
Add rainwater up to 5 cm from the edge
Let ferment with a floating lid
When there are no more fine bubbles rising due to fermentation, the extract is ready.

Fermentation lasts about 15 days at a temperature of 18 to 20°C.

Filter carefully
Dilute to 5-10% for foliar spraying and 20% for soil spraying.

Once all these steps are completed, the extract is ready for use.

Dose per hectare:

about 1.5kg of fresh plants macerated for 15 days in 10L of water

This preparation can be stored for several months in an air-tight container, cool and away from light.

Be careful not to mix different plants in the same container as fermentation speeds differ from one species to another.

Cold maceration

Benefits

Stimulation of the natural defenses of plants

Instructions

It is possible to carry out a maceration cold, following these steps:

Let finely cut plant fragments soak in water at room temperature for about 4h
Filter
Dilute to 5% for foliar spraying and 20% for soil spraying

Once all these steps are completed, the extract is ready for use.

Doses per hectare:

100g of dry plants in 5L of water
Let macerate for 4h

Plant juices, instructions

Once the plants of interest are chosen, the steps for making plant juices are as follows:

Coarsely cut the plant
Let the plant ferment alone for 2 days
Press the plant and collect the juice in a container
Filter
Dilute to 3-5% for foliar spraying and 10-20% for soil spraying

Once all these steps are completed, the plant juice is ready for use. Doses per hectare:

1.5kg of fresh plants macerated

Which plants?

The species that may be of interest for vegetable crops are numerous and varied; they can be herbaceous or trees.

The following paragraphs present relatively common plants chosen for the benefits their extracts bring to crops (vitalizing defenses, stimulating soil life, strengthening fungicidal preparations, preventing against frost...). It should be noted that the properties exposed here are based on field observations but not necessarily scientific studies.

Horsetail

Properties

Strengthens the action of fungicides
Energizes growth
Insect repellent

Targets

Main constituents

Silicic acid, alkaloids
Formic acid

Uses

For a fungicidal effect: Decoction of stems
For a stimulating effect: Manure of stems
For an insect repellent effect: Infusion of stems

Be careful, horsetail plant extracts are drying, so they should be used in warm and humid weather.

Nettle

Properties

Insect repellent and insecticide

Strengthens soil microbial flora
Stimulates the natural defenses of plants

Targets

Main constituents

Formic acid
Mineral elements

Uses

For an insect repellent effect: Infusion
For a stimulating effect: Manure
For a fungicidal effect: Decoction of roots
Preparation of biodynamic compost no. 504

The fermented extract can only be used on foliage in warm and dry weather; otherwise, it should be applied to the soil.

Comfrey

Properties

Strengthens soil microbial flora
Promotes cell multiplication (in case of hail or pruning wounds)
Promotes growth: favors seedling growth, improves development and maturation of tomatoes, celery, and cabbages
Activates compost decomposition
Allows release of potash from the soil
Insect repellent plant

Targets

Main constituents

Rich in Potassium, phosphorus, and calcium
Allantoin
Boron

Uses

Fermentations, infusions, concentrated juice of whole plants

Fern

Properties

Insect repellent
Fungicidal

Targets

Main constituents

Rich in silica and potassium
Gallic and acetic acid
Tannin
Prunaside which releases hydrocyanic acid by infusion (fungicide)

Uses

For an insect repellent effect: Manure
For a fungicidal effect: Infusion

Burdock

Properties

Stimulating plant: regulates the stomatal function of the plant, rebalances in case of water stress, and stimulates soil life and vegetation
Fungicidal

Target

Potato late blight

Main constituents

Rich in potassium
Tannins, mucilage, resins, sulfate and phosphate of potash, lime, and magnesia

Uses

Manure

Meadowsweet

Properties

Inductive plant: puts the plant in a state of alert, allowing it to better react to aggressors without cellular abandonment.
Anti-frost plant: protects flowers from spring frost

Main constituents

Salicylic acid

Uses

Infusion at 80°C
Before a predictable attack, use in association with nettle manure and possibly copper and sulfur at 300 g/ha: this can reduce these doses by 30%.
Before frost: Spray the infusion the afternoon before a frost.

Valerian

Properties

Protects against frost: protects flowers from spring frost (down to -2°C)
Heals after hail
Promotes flowering
Stimulating plant

Main constituents

Valeric acid

Uses

Infusions, juices and manures of inflorescences
Preparation of biodynamic compost no. 507
To protect against frost, spray the infusion the afternoon before the frost episode and repeat treatment every 2 days.

To increase frost resistance (down to -5°C), combine with yarrow: infusion of 50% valerian and 50% yarrow.

Thyme, Oregano, Rosemary

Properties

Reducing plants: disrupt the pest detection field and restore polarity on the surface of the diseased plant
Fungicidal effect

Main constituents

Phenols (thymol, carvacrol, eugenol)

Uses

Infusion at 90°C of leaves and flowers

Mint

Properties

Insect repellent and insecticidal plants

Targets

Black aphids, green and gray
Caterpillars

Main constituents

Menthol, menthone, esters

Uses

Infusion at 90°C of leaves harvested before flowering.
It is possible to mix mint, rue, sage, and soapwort together: an association of these plants can achieve up to 80% effectiveness on caterpillars and scale insects.

Rue

Properties

Insect repellent and insecticidal plants

Targets

Repellent against slugs
Aphids
Whiteflies

Main constituents

Essential oils, heteroside, tannin, malic acid

Uses

Infusion of fresh leaves and stems harvested before flowering.
It is possible to mix mint, rue, sage, and soapwort together: an association of these plants can achieve up to 80% effectiveness on caterpillars and scale insects.

Sage

Properties

Insect repellent and insecticidal plants

Targets

Main constituents

Thujone, camphor, aldehydes

Uses

Infusion at 90°C of leaves harvested before flowering.
It is possible to mix mint, rue, sage, and soapwort together: an association of these plants can achieve up to 80% effectiveness on caterpillars and scale insects.

Soapwort

Properties

Insect repellent and insecticidal plants

Targets

Main constituents

Saponin

Uses

Infusion at 90°C of leaves harvested before flowering.
It is possible to mix mint, rue, sage, and soapwort together: an association of these plants can achieve up to 80% effectiveness on caterpillars and scale insects.

Garlic

Properties

Fungicidal
Insecticidal with a very broad spectrum of action
Repellent effect against deer

Targets

Tarsonemid of strawberry
Mites
Aphids
Caterpillars
Colorado potato beetles
Codling moths
Cabbage white of cabbage
Cryptogamic diseases (powdery mildew of cucurbits, moniliosis)
Damping-off
Rust

Main constituents

Sulphides

Uses

Oily maceration from whole cloves.
The persistence of this product is one month.
This preparation can be used against Colorado potato beetles with an efficacy ranging from 0% to 100% (reason for efficacy currently unknown).

Tansy

Properties

Fungicide
Insecticide

Targets

Main constituents

Thujone

Uses

Infusion, decoction or manures of flowers and leaves.
To increase the effectiveness of the preparation, add wormwood to the infusion

Lavender

Properties

Insect repellent

Targets

Aphids

Ants

Uses

Black elder

Properties

Fungicide
Powerful repellent

Targets

Main constituents

Sambucine releasing hydrocyanic acid by infusion

Uses

For an insect repellent effect: Decoction or manure of leaves harvested from April to September.
For a fungicide effect: To increase the effectiveness of the preparation, combine wormwood with the infusion

Rhubarb

Properties

Insect repellent

Targets

Uses

Infusions
Spray undiluted.

Tomato

Properties

Plant stimulation
Insect repellent and insecticide

Targets

Uses

Manure of chopped tomato leaves and stems to spray every 4 or 5 days.
Preventive: against moths of leeks, flea beetles and cabbage whites of cabbage.
Curative: against aphids.

Wormwood

Properties

Insect repellent
Fungicide

Targets

Uses

Manure or decoction

Dandelion

Properties

Promotes fruit ripening
Stimulates the natural defenses of plants

Main constituents

Salicylic acid
Potassium
Ethylene

Uses

Teas of whole plants or flowers
Preparation of biodynamic compost no. 506
Water the soil in spring and autumn
Stimulates growth and improves vegetable quality

What are the advantages?

Natural products allowing significant biodegradability: no risk for groundwater and humans
Many molecules present in plant extracts: multisite actions on pests limiting the emergence of resistance
Possibility of farm preparation
Reappropriation of knowledge by the professional community
Economical technique
Plant-based preparations reduce the treatments needed later on the crop

What are the disadvantages?

Low persistence of action: frequent renewal of treatments
Generally weaker action than synthetic products
Time and variability of preparations
Difficulty in sourcing "finished" extracts
Inadequate and rather heavy regulatory frameworks
Toxicity of "over" extracted products

Sources

This page was created from PDF documents:
- "PLANT EXTRACTS TO TREAT VINES?", published by the Chamber of Agriculture of Var
- "The interest of plant extracts in organic viticulture and arboriculture", published by the CTIFL
- "Plant manures", published by Hervé Georges, professional vegetable grower
- "Technical guide to plant-based preparations", published in 2011 by CIVAM AGROBIO 47, in partnership with the Chamber of Agriculture 47

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