PlantwisePlus Blog

In the search for economical and environmentally friendly approaches to pest control, particularly with chemical resistance becoming an increasing issue, biological alternatives can be important. One such solution lies in the humble chilli pepper. The compound responsible for its heat, capsaicin, is an effective alternative against a range of crop-damaging insect pests.

Chilli peppers: valuable agricultural uses

Capsaicin is the active ingredient in chilli peppers and is derived from plants of the Capsicum genus. While most commonly used in cooking, chilli peppers also have valuable agricultural uses. Capsaicin functions as a repellent for mammals (like elephants) and insects, and also has insecticidal properties. This makes it a useful tool for managing certain insect infestations through home-prepared sprays and in registered commercial products.

Capsaicin is primarily effective against pests such as aphids, loopers, armyworms, spider mites, thrips, leafminers, and whiteflies. When applied to plant surfaces, capsaicin can induce insects to move away from the plant and down to the soil surface. It can reduce egg-laying activity in adult insects, disrupt insect metabolism, interfere with their central nervous systems, and damage cell membranes by causing them to develop holes. This means that capsaicin not only repels insects but can also weaken and kill them. It can be the only active ingredient in pest control products or combined with additional substances such as azadirachtin (from neem), garlic oil, or soybean oil. Capsaicin products are available in different formulations, including granular, dust, and liquid types.

Although capsaicin breaks down rapidly in the environment, making it a relatively low-residue option, it is toxic to honeybees and should requires cautious application. It does not meet the criteria for classification as a Highly Hazardous Pesticide (HHP), but it is labelled as “dangerous” due to potential health risks. Capsaicin can be harmful or toxic if swallowed, and it can cause skin irritation and serious eye damage. For this reason, anyone using capsaicin products should wear protective clothing, including long sleeves, long trousers, waterproof gloves, socks, shoes, and protective eyewear.

Capsaicin: using it effectively

To use capsaicin-based products effectively, farmers should apply them regularly and ensure they come into direct contact with the target pests. For best results, capsaicin should be used as a foliar spray. It is most effective when applied once a week as part of a consistent pest management schedule. During periods of low pest pressure, lower application rates are recommended. However, when pest pressure is high or the plant canopy is thick, higher application rates and more frequent spraying may be necessary. If rain occurs within two to three hours of spraying, the treatment should be repeated. Proper spray coverage is essential, and a minimum of ten gallons of spray per acre is generally required. Larger or woody crops may need higher volumes. Always follow the product instructions and consult your local agro-dealer or extension officer for advice.

Examples of capsaicin to control pest species.

Diamondback moth in Ghana

In Ghana, the diamondback moth is one of the most destructive pests affecting cabbage and other brassicas. This pest can cause up to 60% yield loss. Chemical control has become less effective due to resistance, creating an urgent need for environmentally safe alternatives. Resistance is a change in the sensitivity of a pest population to a pesticide, resulting in the failure of a correct application of a pesticide to control the pest. Farmers can use hot pepper extracts to repel and kill the larvae of this moth.

To make the extract, collect ripe fruits of Capsicum frutescens and remove the stalks before grinding them. Add a few drops of cooking oil and a small amount of local soap (alata samina) to help the solution adhere to the leaves. Leave the mixture overnight and strain it the next morning using a fine cloth. Spray the resulting liquid onto crops at a ratio of 20 grams of pepper per one litre of water using a knapsack sprayer. Repeat this application weekly until one week before harvest.

The extract not only repels the diamondback moth but also allows natural enemies like parasitic wasps to return once the active compound breaks down. Importantly, farmers should wash their hands thoroughly after spraying and wear protective gear to avoid skin or eye irritation. Farmers should also observe a re-entry period of 12 to 24 hours, though the pre-harvest interval is zero, making it safe for use close to harvest time.

Aphids in Zambia

Another example of capsaicin use is for the control of aphids. Aphids are small, soft-bodied insects that feed by piercing plant stems and leaves to suck out the sap. This leads to curling, wrinkling, and stunted growth of the plant. Aphids appear in many colours, including green, yellow, brown, red, and black, and are often found on the undersides of leaves in large groups. They are particularly problematic on crops like beans, cucumbers, pumpkins, tomatoes, potatoes, and cabbage. Since aphids reproduce rapidly, it is crucial to take action early, when there are two to five aphids per plant.

To make a home-prepared chilli spray, crush 1 kg of fresh hot chillies (about 40 to 50 small fruits) and soak them in two litres of water at room temperature for 24 hours. After soaking, strain the mixture through a fine sieve or clean cloth. Just before spraying, add half a cup of liquid soap or three tablespoons of washing powder dissolved in 50 millilitres of water to the mixture to help it stick to plant surfaces.

Farmers should use the solution immediately, as it loses potency quickly and cannot be stored. They should apply the spray thoroughly, making sure to cover both the top and underside of the leaves. A dilution of 300 millilitres of the concentrate in 20 litres of water can treat an area of 1,000 square metres. After spraying, farmers should inspect plants within 24 hours to determine the effectiveness of the treatment.

An economical alternative to chemical pesticides

In summary, capsaicin offers an economical, non-resistant alternative to chemical pesticides for managing certain insect pests. Whether used in traditional hand-made preparations or modern commercial products, chilli-based pest control can protect crops while supporting sustainable farming practices. By adopting capsaicin-based solutions, farmers can reduce chemical inputs, safeguard beneficial insects, and ensure productive food production systems, all by tapping into the power of a naturally fiery plant!

For further information, please visit these additional resources:

Chilli pepper extract for the management of insect pests – Factsheet for Farmers

Using hot pepper to control diamondback moth on cabbage – Factsheet for Farmers

Chilli sprays against aphids in rape vegetables – Factsheet for Farmers

Visit the PlantwisePlus Knowledge Bank for global and country-specific information on crop health and pest management.

PlantwisePlus gratefully acknowledges the financial support of the Directorate-General for International Cooperation, Netherlands (DGIS); European Commission Directorate General for International Partnerships (INTPA); UK International Development from the UK government; and the Swiss Agency for Development and Cooperation (SDC).