Grow your own pesticidal plants

Tithonia diversifolia on Thika Highway in Nairobi. Photo: ICRAF

Tithonia diversifolia on Thika Highway in Nairobi. Photo: ICRAF

Active ingredients found in wild flowers, trees and bramble have been used for millennia to control pests and diseases. Different parts of the plants are processed into decoctions or applied directly to crops or livestock, protecting them from damage, disease and infestation.

A new set of information leaflets, now available for download, describes the insecticidal and medicinal activity of 9 common pesticidal plant species in the tropics and sub-tropics. These leaflets were developed by researchers from the World Agroforestry Centre (ICRAF)’s Tree Diversity, Domestication and Delivery research program, the University of Greenwich and the Millennium Seed Bank Partnership of Kew Royal Botanic Gardens, under the auspices of the African Dryland Alliance for Pesticidal Plant Technologies (ADAPPT) network.

Backed by research findings, the authors describe the properties and uses of these pesticidal plants, as well as where they grow naturally. They further give instructions on how to grow, multiply, harvest and process different parts of the plants—leaves, seeds, fruits, bark, sap, flowers and roots—into botanical pesticides, as well as how to handle and apply these to field crops, stored commodities, or livestock.

Habitats

Many of the plants described grow wild on roadsides and other uncultivated or uncultivable areas. For instance, Kaffir orange (Strychnos spinosa), whose fruits can be processed into a cattle spray, does well on rocks and in sandy soils. Red aloe (Aloe ferox), a good stored-grain protector, grows wild on roadsides. With its bright yellow flowers, the tree marigold (Tithonia diversifolia) is a common sight throughout East African grasslands.

Tephropsia vogelii flower and seed pods. Photo: Phil Stevenson

Tephropsia vogelii flower and seed pods. Photo: Phil Stevenson

Other pesticidal plants, such as the fish bean (Tephrosia vogelii) which works against mosquito larvae and grain borers, are purposely cultivated by farmers as nitrogen-fixing trees, windbreaks, and temporary shade crops. This species is also produced as a commercial ‘organic’ pesticide and used in horticulture and agriculture around the world.

Pesticidal effect

Different parts of these wild plants can be applied directly or used to make pesticidal solutions for spraying.

The leaves of bitter leaf (Vernonia amygdalina) are applied directly to control Sitophilus zeamais, a troublesome weevil of stored maize. Snake apple (Solanum incanum L.) fruits can be crushed and sprayed on cattle to control tick infestation. In Southern Africa, the fruit pulp of spiny monkey ball, Strychnos spinosa, is also crushed and prepared into a cattle spray.

Kale intercropped with Tagetes minuta in Thika, Kenya. Photo: ICRAF

Kale intercropped with Tagetes minuta in Thika, Kenya. Photo: ICRAF

Some of the plants are eaten in soups or, like the pencil tree (Euphorbia tirucalli) and stinkweed (Tagetes minuta), taken as human medicine.

Farming pesticidal plants

Botanical pesticides can be grown on farms and gardens, or harvested along the highways and byways.

But wild harvesting on a large scale is not sustainable, and threatens the diversity of these plants.

Researchers say supply would be improved if people purposely cultivated a range of pesticidal plants, along with farm crops and trees. Growing pesticidal plants gives environmentally friendly pest-control options, and sidesteps the challenges associated with storage, transportation and toxicity of commercial synthetic pesticides, particularly in developing countries.

According to the African Dryland Alliance for Pesticidal-Plant Technologies (ADAPPT), pesticidal plants can also provide marketable products for farmers and small business or cooperatives. Furthermore, their commercialisation will provide both an additional income stream to poor farming communities and a major uptake pathway for business-driven promotion of this proven and effective pest management technology.

Kew’s Millennium Seed Bank Partnership (MSBP), whose mission is to save plants worldwide, notes the critical importance of conserving and preserving wild plant species for benefits now and for the future.

“Wild plants are key to developing innovative, plant-based solutions to the major environmental challenges that we all face, such as food security, water scarcity, deforestation, energy and climate change,” says an MSBP brief.

Download the ‘Pesticidal Plant Leaflet’ series, developed by Parveen Anjarwalla, Lucy Mwaura, Daniel A. Ofori, Ramni Jamnadass, Philip C Stevenson, and Paul Smith. The fact sheets have been created in collaboration with the World Agroforestry Centre and the Royal Botanic Gardens Kew.  More information about these pesticidal species can be found on the Plant Database pages as well through ICRAF’s species switchboard

Download from (OPTIONS) website

Fact sheet about Aloe ferox

Fact sheet about Chenopodium (syn. Dysphania) ambrosioides

Fact sheet about Euphorbia tirucalli

Fact sheet about Lippia javanica

Fact sheet about Securidaca longepedunculata

Fact sheet about Solanum incanum

Fact sheet about Strychnos spinosa

Fact sheet about Tagetes minuta

Fact sheet about Tephrosia vogelii

Fact sheet about Tithonia diversifolia

Fact sheet about Vernonia amygdalina

Fact sheet about Zanthoxylum holtzianum

 

Further leaflets on useful plants are planned as part of the second phase of ADAPPT project.

Related links:

See more on NRI Optimising Pesticidal Plants: Technology Innovation, Outreach and Networks (OPTIONS) website

www.nri.org/adappt
www.kew.org
http://projects.nri.org/adappt/index.htm

www.seedaholic.com

douya@cgiar.org'

Daisy Ouya

Daisy Ouya is a science writer and communications specialist with the World Agroforestry Centre (ICRAF). Over the past 15 years she has been packaging and disseminating scientific knowledge in the fields of entomology, agriculture, health, HIV/AIDS research, and marine science. Daisy is a Board-certified Editor in the Life Sciences (bels.org) and has a Masters’ degree in chemistry from the University of Connecticut, USA. Her BSc is from the University of Nairobi in her native Kenya. She has worked as a journal editor, science writer, publisher, and communications strategist with various organizations. She joined ICRAF in July 2012. Twitter: @daisyouya

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