You can make many biopesticides1 from plant extracts (leaves, fruits, shells, seeds, etc.), which are accessible to small-scale producers. Certain plant compounds, minerals, or organic matter control pests through various mechanisms (modes of action) such as repelling pests or inhibiting the ability of pests to reproduce, molt, and/or feed. This is why neem-based biopesticides are attracting growing interest. Native to South Asia (India) and widely cultivated and/or naturalized in West Africa, the neem tree is renowned for its many benefits, particularly in organic agriculture, owing to its insecticidal, fungicidal, antibacterial, and repellent properties (Nana, 2018). Neem leaves, seeds, kernels, and oil (pressed from other plant parts) are used to formulate natural biopesticides. The primary active compound in neem plant parts is azadirachtin (Isman, 2006), but other molecules such as nimbin, salanin, and gedunin also play important roles in natural pest management using neem (Schmutterer, 1990).

Neem biopesticide acts mainly as a repellent (preventing pests from settling), a growth inhibitor (blocking insect molting and/or reproduction; Ba Loua, 2017), and a sterilizing agent (preventing egg-laying or rendering eggs non-viable; Das A., 2022) depending on the pest. This article presents several neem-based biopesticides popularized by ECHO West Africa. These biopesticides are based on the experience, indigenous knowledge, and know-how of farmers.

All neem-based biopesticide products should be kept away from direct sunlight (in the shade) to minimize sunlight breaking down the main active ingredient, azadirachtin.

1. Biopesticide based on fresh neem leaves

The biopesticide based on fresh neem leaves is a very simple, natural pesticide to make.

Ingredients

• 1 kg of fresh neem leaves (Figure 1)
• 5 L of water 2
  2If your water source is connected to community water treatment facilities, ensure that chlorine levels are not too high as this could inhibit microbial life. Consider instead, using a local ground water source or water from a stream.
• 5 mg of local soap3 (15 ml [1 Tablespoon])

Materials needed 

• Mortar
• 6 to 10 L container 
• Filter (cloth or piece of mosquito netting) 
• Sprayer

Preparation 

1. 

   Weigh and crush 1 kg of fresh neem leaves 
2. Put the crushed leaves in 5 L of cold water (Figure 2) 
3. Let steep for 24 hours 
   The next day 
4. Remove the leaves from the water 
5. Filter thoroughly using a fine cloth 
6. Add soap (5 mg)

Note: Use filtrate immediately after production; it cannot be stored for more than one day.

Use

• Pour the filtrate into the sprayer without dilution (do not add any additional water).
• Spray on all sides of the leaves (ensure thorough coverage).
• Spray once a week.

Note Neem’s action is not immediate: it does not kill insects directly but blocks their development by causing a loss of appetite (they starve), blocking their reproduction, preventing their molting, etc.

Target pests

This preparation can be used to control fungal diseases, soil-dwelling insects, nematodes, and insect pests of vegetable crops.

2. Neem seed-based biopesticide

Ingredients

• 5 kg of mature neem fruit (Figures 3 and 4) 
• 10 L of water
• 5 to 10 mg soap

Materials needed 

• Mortar
• Sieve
• Bucket
• Sprayer

Preparation

To make the neem seed-based biopesticide, the following steps are required:

1. Collect 5 kg of fruit that have fallen from the tree. Use only ripe fruit that are yellow or brown/chocolate in color (Figure 4).
2. Soak them in water for 24 hours to remove the outer skins and obtain the husks (shells) containing the kernels (Figure 5).
3. Dry the husks containing the kernels in full sun for at least a day.
4. Gather husks containing kernels (are not empty).
5. Crush them with a mortar and pestle to obtain a coarse powder (Figure 6).
6. Place the resulting product in a plastic container (a lidded drum, a lidded bucket,4 etc.).
7. Add 10 liters of water to it.
8. Let the mixture steep for 24 hours.
9. Filter the resulting product.

Use

• Place the resulting product in a sprayer apparatus, add 5 to 10 mg of soap, and spray without dilution (do not add water).
• Spray in the morning before 9 a.m. and in the evening after 4 p.m. 
• The powder alone can be stored; however, once mixed with water, the product must be used on the day of filtering.

Target pests

This preparation can be used to control cabbage worm, whitefly, and chewing insects (caterpillars and crickets).

3. Neem kernel powder-based biopesticide

Ingredients

• 1 kg of neem kernels
• 16 L of water
• 10 mg of soap

Materials needed 

• Mortar
• Bucket
• Scarf or sieve
• Sprayer

Preparation

1. Weigh 1 kg of neem kernels and grind them into powder (Figure 7).
2. Put the powder in a bucket, add 16 L of water, mix thoroughly and cover (Figure 8, 9 and 10).
3. Let the solution steep for 24 hours away from sunlight, then filter.

Use

• 

  Put all the obtained filtrate in a sprayer and add 10 mg of soap, grated (Figure 11).
• Do not dilute (do not add more water).
• Apply directly to crops by spraying.
• Treatments should be carried out in the morning before 9 a.m. or in the evening after 4 p.m., preferably once a week.

Target pests

This preparation can be used to control cabbage worm, whitefly, and chewing insects (caterpillars and crickets).

4. Neem oil

Neem oil has numerous benefits. Neem oil is sold and provides fairly substantial income for stakeholders in the industry.
It is used in cosmetics as well as for human, animal, and plant health. 

Ingredients

• Neem kernel powder if needed or neem oil
• Water
• Soap

Materials needed 

• Container (preferably a plastic tray) if necessary
• Sprayer

Preparation

How is neem oil extracted?

1. If one does not have neem kernel powder directly available, the first step is to collect ripe (yellow-colored) fruit that have fallen from the neem tree. One can also collect dried, browned fruit, but blackened fruit should be avoided as they are rotten.
2. After collecting/gathering the fruit, submerge them in water.
3. The next day, stir the fruit to remove their outer skins.

4. 

   This yields the neem husks (surrounding the kernel) which are then crushed to obtain the kernels.
5. By pounding the kernels, one obtains neem kernel powder.
6. It is from this neem kernel powder that the neem oil is extracted. To obtain 1 L of neem oil, 3 kg of neem kernel powder is required. Pour a quantity of neem kernel powder into a container, add a little water and knead it to form a hard paste. By pressing the paste against the tray, the oil gradually seeps out (Figures 12 and 13).

Use of neem oil in agriculture

Preventive mode

• Use 1 L of neem oil with 100 L of water (plus 60 to 75 ml [4 to 5 tablespoons] of soap) per hectare. 
• Always treat before the appearance of flowers and just after the appearance of young fruits. 
• Then continue during fruit enlargement until physiological maturity.
• Spray at intervals of 10 to 15 days.

Curative mode

• Use 2 L of neem oil with 100 L of water (plus 60 to 75 ml [4 to 5 tablespoons] of soap) per hectare.
• Always treat before the appearance of flowers and just after the appearance of young fruits.
• Then continue during fruit enlargement until physiological maturity.
• Spray at intervals of 10 to 15 days.

Target pests

Neem oil is a veritable shield for plants; it repels various insects and blocks the metamorphosis of larvae, making it a highly effective natural solution. 

It repels mosquitoes, midges (Ceratopogonidae), lice (infra order Phthiraptera ), caterpillars (Lepidoptera), ticks (class Arachnida suborder Ixodida) or soft ticks (suborder Argasidae) etc. It also helps to control certain fungi, parasites, insects, and bacteria.

Thus, neem oil serves as a fertilizer (foliar fertilization), a stimulator of natural defenses, and a repellent for use in vegetable, fruit, and forest crops.

Neem oil also enables the implementation of effective and environmentally friendly processes for crops requiring pesticides (against pests), including fungicides (against fungi) or insecticides (against insects).

Table 1 shows insects controlled by neem preparations described above.

In piggeries, chicken coops, and other animal operations, neem oil is used to treat parasites (ticks, lice, flies [order Diptera], etc.) and parasitic infections (e.g., scabies [Sarcoptes scabiei]).

Conclusion and recommendations

The use of neem-based biopesticides is an environmentally friendly, economical, and accessible solution for small-scale producers. Using neem in integrated pest management contributes to sustainable agriculture without compromising human health or the environment. By utilizing different parts of the neem tree, farmers can produce their own inputs, reduce their dependence on chemicals, and improve the resilience of their crops.

Practical recommendations for farmers for greater effectiveness: 

• Apply treatments early in the morning or at the end of the day to avoid degradation of azadirachtin by the sun. 
• Respect the recommended doses to avoid phytotoxicity.
• Combine with other integrated pest management methods (traps, rotation, nets) (CIRAD, 2014).

References