Neem (Azadirachta indica) is a tree belonging to the Mahogany family and native to South Asia. Renowned for its proven medicinal and pesticidal properties, it has been relied upon in India for centuries, where it is variously known as “Divine Tree”, “Heal All”, “Nature’s Drugstore”, and “Village Pharmacy”. In Kenya it has been dubbed “arobaini”, because it cures “40” diseases.

As plants have evolved to avoid being eaten, many contain compounds which are distasteful or toxic to insects (no miracle, if you believe in evolution…). Thus, traditional herbalists and scientists from around the world have used their knowledge about plants’ natural defences to identify and develop pesticides.

Extracts from various parts of the Neem tree (leaves, flowers, bark, and oil from the seeds) contain one or more of a complex range of active ingredients, the most important of which is ‘azadirachtin’ being the primary active compound. Because the active ingredients in Neem have very complex molecular structures, it is not feasible to manufacture them synthetically. One of Neem’s widely promoted uses is as a natural pesticide by small scale organic farmers (one of the reasons it has been promoted in Rwanda – the idea being that they can grow their own biopesticides on farm to reduce pest predation of their crops). When they identify a pest problem, or as a preventive measure, farmers can pound and soak Neem tree leaves for a night and then spray. Neem oil is extracted from the seed, contains quite a different combination of chemicals, and works rather differently. Neem-oil products are reportedly effective against aphids, whiteflies, scale crawlers, and spider mites,

but are generally not effective against mealybugs, weevils, thrips, or adult scales. Neem oil can also be used as a household pesticide for ant, bedbug, cockroach, housefly, sand fly, snail, termite and mosquitoes both as repellent and larvicide.

Extracts of Neem do not immediately knock down, or kill insects, but adversely affect their feeding, breeding and metamorphosis processes particularly in the juvenile stages. Growth-regulatory effects of Neem products are not instantaneous, however, so users must be patient, because treated insects will continue to feed (albeit at a reduced rate) before the effects of Neem are manifested. Azadirachtin has no growth regulatory activity against adult stages, but does possess repellent activity, deterring some insects (such as grasshoppers) from feeding or laying eggs on treated plants.

It is claimed that only the insects that feed on plant tissues actually succumb. Those that feed on nectar (butterflies, bees, etc) or other insects (such as spiders, and ladybirds) tend to survive. Thus some promote Neem as a ‘selective’ biopesticide that gets the bad guys, while saving the ‘good guys’ (depending on your view of spiders!). However, larvae (including caterpillars) are highly susceptible so it’s not all perfect.

In spite of its limitations, Neem has many advantages – it is natural and non-toxic to mammals (hence can be used in organic crops, and indoors), and quickly breaks down in the environment posing no long term toxicity problems - though on the other hand this means it must be reapplied regularly to retain effectiveness.

As a human medicine it has an enormous range of uses in folk remedies, but is particularly prescribed for skin conditions such as acne (antibacterial), eczema, and fungal infections, typically through inclusion of Neem Oil in cosmetics such as soaps, shampoo, balms, creams. It can also be used as an anthelmintic (treating intenstinal worms) through drinking of a rather bitter ‘tea’ made with bark and/or leaves. Some claim that it also treats headlice, and scabies, viruses and infertility. Neem twigs have for long been used for brushing teeth in India, Bangladesh and Pakistan, representing perhaps one of the earliest and most effective forms of dental care. Today, Neem oil is included in some toothpastes.

It thrives in most parts of Rwanda, and is noted for its tolerance of a wide range of soils, and its drought resistance. It will grow in full sun to partial shade, growing best in a well-drained soil mix, with some sand. It is fast growing and typically reaches a height of 15-20m. With white and fragrant flowers, and a yellowish-white fruit, Neem has been widely planted in gardens around the tropics (Rwanda being no exception), often solely for its ‘ornamental’ and ‘curiosity’ value and never being used.

Along with Moringa, Neem has in the past been promoted in Rwanda as a ‘miracle tree’ that will solve all farmers’ problems – primarily through potential for sale, and export of Neem products. Neem seed extracts have indeed been exported in limited quantities from India, Australia and Africa and marketed to organic farmers in Europe and America under brand names such as “BioNeem”. But those promising future riches to those who bought their over-priced seed / seedlings seemed to be unable to assure access to these markets, and many farmers invested time and money, but were disappointed. But there are still good reasons to at least one in your garden, and prepare some extracts to keep those aphids and mealy bugs away?

I will not recommend any ‘preparations’ of pesticides or medicines – for that you need to consult a specialist, or do your own research – there are masses of websites, and many entire books written about Neem alone!