By Felix Ochieng Akech

Demand for neem is rising by more than 20 per cent a year in many African nations as farmers discover its power with pests and soils, but as a plant and spray that can poison livestock and bees, respect of its potential to be toxic is essential.

For many insects, neem gives strong protection with frequent spraying.

Vegetable farmer Derick Onyambu from Uriri said his vegetable losses to armyworms and aphids have halved since he began weekly neem sprays.

“I used to spend over Sh2,000 a month on chemicals. With neem I spend almost nothing, just time to prepare it,” he said. 

In nearby Rongo, Shamim Anyango now boils neem seed liquid to use on her goats. “I haven’t bought acaricides for months,” she said.

In fact, neem works well against sap-sucking insects like aphids, whiteflies, and thrips, where regular spraying reduces feeding and reproduction. It also helps with soft-bodied pests and some caterpillars, slowing larval growth and lowering damage over time. 

On livestock, neem seed extracts have killed ticks and other parasites in trials, though success varies with the strength and preparation.

But neem struggles with fast-acting pest problems. It does little against fruit flies, stem borers, and other deep-boring insects that require immediate control. 

Because its active compounds break down in sunlight within hours, neem’s protection can also be short-lived unless farmers reapply it regularly.

Even so, different preparations make it useful in many situations. A simple neem leaf soak works well for vegetables and seedlings on small plots, while cold-pressed neem oil gives stronger, longer protection in orchards or where pest pressure is high. 

For livestock ticks, a 10 per cent seed decoction can work, but farmers need to first test it on a few animals.

Farmers can also improve results by spraying in the early morning or late evening, when sunlight is weaker, and adding a little soap or oil to help the spray stick and last longer. 

Experts recommend using neem as part of integrated pest control, alongside field hygiene, scouting, traps, intercropping, and natural enemies, since it spares most beneficial insects and reduces chemical use.

Used carefully, neem is low in toxicity to people and most farm-friendly insects. But concentrated sprays can harm some predators, flowering crops and livestock

Peer-reviewed studies have found neem sprays can harm some helpful insects if used in strong concentrations or sprayed directly on them. Laboratory tests found that lacewings, ladybird beetles and parasitoid wasps exposed to neem extracts above 0.5 to 1 per cent suffered delayed growth and lower survival, and some lost up to half of their eggs’ hatching rate. The safe boundary is to use dilute sprays and avoid spraying when bees or predators are active.

Research has also found neem istoxic to honeybees when freshly sprayed, with lab tests recording bila killed at an average 15–25 micrograms dose per bee. In field trials, bees foraging on crops sprayed in the late evening had almost no losses, as the toxic residues became harmless to bees after drying or sunlight. The boundary is therefore to avoid spraying open flowers or fields where bees are feeding, and to apply neem only before dawn or after sunset when bees are not active.

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Neem can also harm livestock, with neem leaves and seed cake safe as feed only in very small amounts. Broilers fed rations with 5 to 10 per cent neem leaf meal ate less and grew 10 to 30 per cent more slowly because of the bitter compounds. Other tests found that feed with more than 2 per cent leaf meal or 1 per cent seed cake caused liver and kidney stress in goats and poultry, making it unwise to use neem in feeds.

Beyond pest control, neem trees bring extra value as organic fertilizer, and the the pressed oil and seeds can be used to make soaps.

As a cheap, practical tool that cuts costs and lowers risks. neem is almost unequalled, but as farmers experiment with it, it’s vital to avoid those few spots where it is harmful and toxic.

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