Neem in the News, June 2017

 In Neem in the News, Neem Research

A new report on neem as a biopesticide is particularly appropriate as weather heats up and pests become a problem almost everywhere. Neem was “discovered” in the western world in 1959 when a German entomologist noticed that the only green standing after a swarm of locusts swept through the Sudan was the neem trees brought by Indian immigrants.

Nearly 60 years (and more than 1,100 reports) later, a new review of the literature looks at how neem works as a pesticide and describes new strategies to make it more effective.

Published in Frontiers in Plant Science, the report begins by noting that 90% of applied pesticides actually run off the plants they’re applied to and into the environment – not to mention the pesticides that stick to the food we eat.  According to the World Health Organization, pesticides are responsible for poisoning three million people and causing about 200,000 deaths.

Neem, on the other hand, is so non-toxic that it is being used as a biomedicine as well as a biopesticide. Its key ingredient, azadirachtin, acts as an antifeedant, repellant and induces sterility by preventing oviposition, disrupting larva from molting and interrupting sperm production.

Neem oil, made by extracting oil from seeds, is the primary agent used as a pesticide. Because it contains so many active ingredients, pests are highly unlikely to develop resistance to it. In the tropics, where neem is easy to grow and pests are ongoing threats, neem leaf can be fed to worms, which grow faster than when fed other food, and create vermicompost that helps protect plants. It also can be added to organic fertilizers to improve the resistance of plants to aphids.

As mosquitoes become more important pests, one study reports a 100% mortality in one species of mosquito larva after seven days and more than 90% in other species.

Still, some issues remain. Like most biopesticides, neem has a short shelf life when exposed to sunlight. Some researchers are using nanotechnology to formulate neem products with “controlled release” properties to improve stability and effectiveness. (The review didn’t evaluate neem soil drenches, which have lasted for up to six weeks in my own garden, particularly on difficult pests like cucumber beetles which lay eggs that burrow into stems and can’t be treated with any kind of spray.)

Another issue, which I have never personally encountered, is the herbicidal properties in two of neem’s active ingredients. A report published in the journal Molecules shows that nimbolide and nimbic acid inhibit the growth of cress, lettuce, alfalfa, timothy, crabgrass, ryegrass, barnyard grass and jungle rice.

New research also suggests that it may be more dangerous for beneficial insects than previously believed, including a predatory stink bug. (However, researchers have shown that neem is beneficial to bees, even when applied directly to them.)

The full report is available online at with hyperlinks to the research it cites. To buy NimBioSys EPA-registered neem oil, click here


*   This article is published for informational uses only. Neem Tree Farms does not sell products which are intended to diagnose, treat, control or cure any disease, or to repel any insect from people or animals.

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