The use of plant-derived pesticides (commonly called "botanicals") in pest management is widespread cultural practice for many smallholder and subsistence farmers across Africa. A wide range of botanical insecticide products are used by farmers, with the formulation based on local indigenous knowledge of the local plants and products that can be used for insecticidal activity. The mode of action of botanical pesticides is broad and ranges from repellency, knock-down, larvicidal to anti-feedant, moulting inhibitors and growth regulation. However, the efficacy of such products is often unreliable as it is difficult to obtain a standard active ingredient formulation that consistently works. Sometimes the formulations can ferment and become very toxic for human exposure and for the environment, ie. some tobacco extract formulations. For this reason, such home-made botanical products cannot be registered in South Africa under the Agricultural Remedies Act (Act 36 of 1947), and agricultural officials are not allowed to advocate or recommend any botanical concoctions.
Despite the concerns, the use of home-made botanical insecticides is often the only remedy available to resource-poor farmers in Africa and we need to be realistic and work with farmers to ensure that their products are safe. In fact, while cost-effective and readily available insecticides are being registered against FAW, the botanicals offer an important weapon against FAW for many farmers. Farmers generally extract bioactive compounds as a concoction after grinding up plant materials and soaking using water. Essential oils from bioactive rich plants and powdered forms are also used to some extent.
There are comparative advantages associated with the use of botanicals:
they are biodegradable and do not accumulate in the environment
generally less harmful to farmers and consumers (though there are some exceptions); and
they often are less toxic to natural enemies (predators and parasitoids), hence not disrupting ecosystem services delivered by these natural enemies.
Preliminary evidence from other parts of the world indicates that seeds or leaves of plants of the Meliaceae family (Azadirachta indica, i.e. neem and Melia) and Asteraceae family (Pyrethrum), and other plants such as Tephrosia vogelii or Thevetia neriifolia, are showing efficacy in the management of armyworms.
In future, it may become important to assess the compatibility of botanical pesticides with other pest management options such as pheromones and entomopathogens, in order to optimize low-cost and effective pest management strategies for FAW.
Integration of botanical pesticides with management options such as Push- pull/Intercropping; pheromones, and less toxic synthetic pesticides as a last resort, is critical to achieve effective management of FAW.