Plant protection substances/active ingredients
Pyrethrins
Pyrethrins are extracted from flowers of Chrysanthemum cinerariaefolium. Kenya is one of the leading producers of natural pyrethrum.
Pyrethrum is an insecticide with broad spectrum of activity and is effective against most aphids, cabbage loopers, leafhoppers, spider mites, stink bugs, thrips and whiteflies. Pyrethrins can damage beneficial organisms.
Pyrethrum products can be produced on-farm, but are more easily, more safely and more reproducibly produced under industrial conditions.
Pyrethrum must not be confused with pyrethroids. Synthetically produced pyrethroids are not allowed in organic farming. Pyrethrum is often combined with piperonyl butoxide (PBO). Some organic labels allow PBO, while others prohibit its use.
Application against
Aphids
Lice
Moths
Loopers
Spider mites
Stink bugs
Mode of action
Obtained from chrysanthemum species.
Contact poison that rapidly enters the nervous system of insects and leads to paralysis and death.
Often addition of sesame oil to enhance the effect.
Impact remarks
Rapid disintegration on contact with sunlight and air
Side effects
Broad spectrum of action; also partially harms beneficial insects.
Very toxic to aquatic organisms with long lasting effects,
Hazardous to bees
Application
Not miscible with sulphur lime, bicarbonates and bacterial, yeast and alumina preparations.
For good treatment success, ensure good wetting of the insects before the leaves roll up using plenty of water, high application pressure, and good application technique.
For a long duration of effect, carry out the treatments in the evening or early morning.
Better effect through addition of soap preparations
Waiting period: 3 weeks
Neem extracts (azadirachtin)
Neem trees are widespread in Africa. Leaves and seeds are collected commercially by farmers and small industrial producers. Neem has an intermediate spectrum of action. It is effective against more than 400 pests such as African armyworm, African bollwom, aphids, Banana weevil, Cabbage looper, Cabbage moth, Cabbage webworm, Coconut mite, Cutworms, Diamondback moth and Giant looper. Neem products generally do not harm natural enemies of pests like wasps, ladybird beetles, etc. However, neem products with a high oil content can harm certain beneficials and have phytotoxic effects to some plants.
On-farm production of Neem inputs is possible. In Africa, many commercial products from different suppliers are available including mixtures of neem seed oil or extract with other natural ingredients.
Neem oil or seed extract can have a preventive effect against plant diseases such as mildews and rusts. Due to phytotoxic effects, Neem extracts should be tested on a few plants before using them at a large scale.
Application against
Beetle larvae, butterfly and moth caterpillars
Stalkborers
True bugs, plant- and leafhoppers, grasshoppers
Adult beetles
Thrips, fruit flies, scale insects, mealybugs
Mites
Aphids and whiteflies
Plant parasitic nematodes
Mode of action
Extract from the seeds of the neem tree (Azadirachta indica) with many active components.
Azadirachtin, the main active ingredient, can be taken up by the plant and translocated through the leaf but not in the sap stream.
Impact remarks
Neem extracts inhibit larval development and reduce the ability of insects to reproduce (delayed but high effect).
Side effects
Hazardous to bees
Toxic to aquatic organisms with long lasting effects
Application
Not miscible with lime sulphur, alumina preparations and oils
Effective against aphids even after the leaves have curled up, due to frassing toxin and translaminar distribution of the active ingredient in the leaves
Good wetting is crucial for the success of the treatment.
Application: before or after flowering in fruit crops.
Bacillus thuringiensis
Bacillus thuringiensis (Bt) has, as other microorganisms or microbial biocontrol agents mostly do, a very narrow spectrum of action. Bt is a naturally occurring soil bacterium. The different Bt strains are effective against armyworms, bollworms, webworms, moths, loopers, leafworms and borers. Bt is not toxic for beneficial organisms and humans.
Inputs made from microorganisms are produced in industrial processes and are available only as commercial products. Bt products are available from agricultural suppliers in most African countries.
Bt-products are ideal for pest management in the tropics due to their easy application, high virulence and narrow host specificity. Bt is a living organism. It is sensitive to high temperatures and has a limited shelf-life.
Application against
Armyworms, bollworms, and webworms
Moths
Loopers
Leafworms
Borers
Mode of action
Bt preparations consist of protein crystals from bacterial spores.
Digestion activates the protein crystals and they form toxins that bind to the midgut wall and dissolve cells there. The digestive system is destroyed and the caterpillars die.
Impact remarks
The younger the caterpillars at treatment, the better the effect.
At less than 15 °C, the frassing activity is too low and thus the effect is insufficient.
Side effects
None known
Only effective against certain butterfly caterpillars, therefore selective and beneficial insecticide
Application
Not miscible with alkaline agents and additives as well as potassium soap, pyrethrin and copper products.
Only carry out treatments at more than 15 °C atmospheric temperature.
Carry out treatments before or after flowering.
Fatty acids (potassium soaps)
So-called soft soaps are harmless and non-toxic for humans and the environment. They have a limited spectrum of activity and are effective as insecticide against aphids, mealybugs, spider mites, African armyworm, thrips and whiteflies. In addition, soft soaps can also be used as a spreader/sticker to improve the effectiveness of other pesticides.
On-farm production of soft soaps is questionable, whereas small-scale industrial production is possible. So far, there are not many commercial products available in Africa, but many from suppliers overseas. In Africa, many soft soaps made of palm oil or palm tree by-products are available on the market.
The effectiveness against the different pests may have to be tested in local conditions. As the soap spray may injure the foliage of crops (e. g. kales), the products should be tested on a few leaves, and checked after 2 days, before being applied on a full scale.
Application against
Spider mites
Aphids
Mealybugs
African armyworm
Thrips
Whiteflies
Mode of action
Reduce the surface tension of the water, which allows them to penetrate the insects’ respiratory tubes, causing them to suffocate.
The strongly alkaline solution has an additional osmotic effect and dries out thin-skinned insects.
Impact remarks
Soap products wash off quickly and have low stability under ultraviolet (UV, direct sun) light.
Fatty acids enhance the effect of pyrethrin.
Side effects
Only minor impairment of beneficial insects
Fruit russeting possible with repeated treatments (especially at high temperatures).
Treatments into the flower can have a thinning effect that is difficult to assess.
Harmful to aquatic organisms with long lasting effects.
Application
Only miscible with pyrethrin and quassia (Quassia amara, bitter-wood) extracts
Perform treatments in the evening or early morning.
The time of application and optimal wetting through a suitable application technique are crucial.
Waiting period: 1 week
Rapeseed oil, white oil
Oils for plant protection can be obtained from various oil plants, or from mineral oil (white oil). They have an intermediate spectrum of activity and are partially effective against aphids, scale insects, spider mites and thrips. Oils can also harm certain beneficial organisms.
On-farm production of oils is not recommended, whereas local small-scale industrial production is possible for plant oils. Botanical and mineral oils are available as commercial products from international suppliers.
The effectiveness of oils should be tested under local conditions. Oils are also used to as additives to insecticides to increase their adhesion and performance.
Application against
Scale insects
Spider mites
Frost moth
Mites
Aphids
Mealybugs
Citrus leaf miner
Smooth skinned caterpillars
Mode of action
The oil film coats and suffocates the pests and their eggs.
White oil also has an insecticidal contact effect.
Rapeseed oils can also be used to improve wetting and adhesion properties (check approvals and miscibility).
Impact remarks
Better effect in warm, dry weather due to stronger respiration of the animals
White oils are slightly more effective than vegetable oils, but are degraded more slowly.
Side effects
Hardly any side effects, but observations under local conditions is encouraged.
Application
Check miscibility with other products.
Miscible with copper, but not recommended due to the different amounts of water required.
Good wetting (until shortly before dripping) is crucial for success. If necessary, divide treatment into two applications with the same amount of broth, but half the concentration.
Only use before flowering.