The use of chemical insecticides and pesticides can be expensive and therefore not an economically viable option for small scale farmers, while also not being climate smart – widespread use of pesticides and herbicides contributes to greenhouse gas emissions. Encouraging natural predators can be an effective method for controlling and managing pests in some instances. With governments across the globe discouraging the use of chemical insecticides and pesticide products, biological control of pests is preferred and encouraged - using living organisms to control pests. Natural predators are insects that feed on pests without damaging the crop and can be found throughout the crops. Encouraging natural predators helps in supressing pests during their early and late lifecycles, improving crop production and reducing pollution caused by pesticides use. The introduction of water-fowl, such ducks in rice systems can be a highly effective form of biological control of pests. They enjoy aquatic habitats, consume insects and can even contribute to weeding as tear up weed plants as they look for food. Insect predators have different roles in controlling pests, there are predators that will control pests in the early pest lifecycle where they feed on their larvae and eggs while some are present at the late pest cycle where they feed on mature insects. Some species of ants are natural predators of stemborer pests, and wasp and some fly species larvae are parasitoids (larvae that feed on a host organism) prey on fall armyworm. One such wasp is the tiny (3 mm in length) Cotesia marginiventris which feeds on FAW caterpillars. The minute (0.5 mm in length) Trichogramma was species lays it’s eggs inside FAW eggs, killing the FAW larvae in the process. Earwigs (Dermaptera: Forficulidae, Carcinophoridae), ground beetles and ladybird beetles are also known to prey on FAW caterpillars. The issue with many of these solutions is volume of consumption, which may be too low to impact an infestation. Ants are the most important predators of FAW, as the communities consume larger quantities of FAW. However, pesticides drastically impact ant populations.
To effectively leverage biological control and encourage natural predators:
- Step 1: Conduct regular monitoring using field walk-throughs and utilise bottle traps with various lures/baits to identify main pests on crops in order to identify any pests.
- Step 2: Once the pests have been identified, consult with national research institutes to identify the best natural predators, or biological control agents* to address the particular pests. It is critical to understand what options are available and costs associated with each option.
- Step 3: Implement according to advice received.
- Step 4: Monitor progress in terms of reduction in numbers and incidences.
- Step 5: Adjust the approach based upon observations from the fields.
A farmer must study the lifecycles of insect predators and be aware of pests that feed on his/her crops in order to identify the intervention that will the most effective in controlling pests at difference phases of their lifecycles. Farmers can create welcoming environments for certain predators to attract them to the field area
- Allen Smith, P. 2014. 17 Plants to Control Pests. P. Allen Smith Garden Home website.
- The Food and Agriculture Organisation, 2018. Integrated management of the Fall Armyworm on Maize: a guide for famer field schools in Africa. Rome, Italy.
- Farmers website (Kenya) 2019. How farmers can use ducks to control pests. Nairobi, Kenya.
- Midega, Charles & Khan, Zeyaur & Van den Berg, Johnnie & K. P. O. Ogol, Callistus & Pickett, John & J. Wadhams, Lester. (2006). Maize stemborer predator activity under ‘push – pull’ system and Bt-maize: A potential component in managing Bt resistance. International Journal of Pest Management. 52. 1-10.
- National Geographic 2016. Want cleaner rice paddies? Find a flock of ducks. Washington DC. USA.
Benefits
- Encouraging natural predators helps improve crop production, reduces the use of pesticides which can pollute both the crop and environment.
- Introducing a natural predator, or biological control agent can reduce the risk of crop failure, and increase agricultural productivity.
- Archytas, Winthemia and Lespesia flies prey on FAW eggs, with the fly-maggots feeding on the FAW larvae in order to grow. And ants can be highly effective predators of FAW.
- Ducks are highly effective in rice paddy fields.
Drawbacks
- Natural predators are often highly specific to a certain predator, and location/geography/climate; hence, research must be done to establish the most effective method of control.
- Some natural predators do not consume enough prey to reduce infestations, meaning despite best efforts, crops may still fail.
