TWN Info Service on Sustainable Agriculture
16 August 2023
Third World Network
www.twn.my
Dear Friends and Colleagues
Push-Pull System Sustains Pest Control and Increases Maize Yields Over Time
A study (Item 1) assessed the extent to which the introduction of the “push-pull system” in western Kenya has impacted variations in crop yields and pest abundance for insects and parasitic weeds over time. It found that pests declined with time in both push-pull and nearby control fields, while yield improved with time in push-pull fields. The data suggest that the push-pull system actually gets better the longer it is established, maintaining consistently high yields, usually between double and triple yields, compared to farms with non-push-pull systems (Item 2).
The push-pull system uses two companion crops alongside a main crop such as maize, with the “push” plant (such as a legume) planted in rows in between maize and the “pull” plant (such as Napier grass) planted as a perimeter around the edges of the maize field. The “push” plant repels adult female moths when they look for a place to lay their eggs. The females then travel to the edge of the field and are attracted to the “pull” plants, which attract them to lay their eggs but are poor hosts, thereby leading to at least 80 per cent of the larvae dying before reaching adulthood.
The finding that the abundance of pests in the push-pull system decreased over time suggests that the benefits for pest control could last for many years. The researchers add that ecologically intensified pest management systems such as push-pull systems are more durable than chemical pesticides, as pests frequently evolve pesticide resistance but rarely adapt to overcome ecologically intensified systems.
With best wishes,
Third World Network
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Item 1
ARE PESTS ADAPTING TO THE PUSH-PULL SYSTEM? ECOLOGICALLY INTENSIFIED FARMS IN KENYA MAINTAIN SUCCESSFUL PEST CONTROL OVER TIME
By T. Luttermoser, Z.R. Khan, C.A.O. Midega, D. Nyagol, M. Jonsson, K. Poveda,
Agriculture, Ecosystems & Environment,
Volume 347, 2023, 108345,
https://doi.org/10.1016/j.agee.2023.108345
https://www.sciencedirect.com/science/article/abs/pii/S016788092300004X?via%3Dihub
1 May 2023
Abstract
Ecological intensification utilizes biodiversity to maintain agricultural yields while reducing negative environmental impacts. While pest management is a common goal of ecological intensification, studies examining ecologically intensified pest management systems over longer time scales are rare. Using the push-pull system in Western Kenya, we examine whether pest abundance (for both insects and parasitic weeds) and yield vary with time since a given push-pull field was established. With a total of 1880 data points from 476 unique farmers and 24 cropping seasons, we found that pests declined with time since establishment in both push-pull and nearby control fields, while yield improved with time since establishment in push-pull fields. Although this study did not directly address mechanisms, it seems likely that pests in the push-pull system are not successfully adapting to overcome its pest management effects given the continued declines in pest abundance over time. Our data suggest that ecologically intensified agriculture may be resilient against pest adaptation over time, maintaining consistently high yields.
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Item 2
PUSH-PULL TECH ‘CONTROLS PESTS, INCREASES MAIZE YIELDS’
By Gilbert Nakweya
SciDev.Net Sub-Saharan Africa English desk
https://www.scidev.net/global/news/push-pull-tech-controls-pests,-increases-maize-yields/
8 June 2023
[NAIROBI] So-called “push-pull” agricultural practices that aim to improve crop yields by minimising the use of synthetic herbicides and insecticides increases yields and prevents pests from adapting over time, a study shows.
Researchers on the study, published in the 1 May edition of the journal Agriculture, Ecosystems and Environment, assessed the extent to which the introduction of the push-pull system in western Kenya has impacted variations in crop yields and pest abundance for insects and parasitic weeds over time.
According to the researchers, the push-pull system uses two companion crops alongside a main crop such as maize, with the “push” plant (such as a legume) planted in rows in between maize and the “pull” plant (such as Napier grass) planted as a perimeter around the edges of the maize field.
The “push” plant repels adult female moths when they look for a place to lay their eggs. The females then travel to the edge of the field and are attracted to the “pull” plants, which attract them to lay their eggs but are poor hosts, thereby leading to at least 80 per cent of the larvae dying before reaching adulthood.
“The key finding of our study is that push-pull actually gets better the longer it is established,” said Tim Luttermoser, the study’s lead researcher and a doctoral student at Cornell University’s Department of Entomology in the United States.
He tells SciDev.Net that the push-pull combination technology led to “massive yield benefits for farmers”, usually between double and triple yields compared to farms with non-push-pull technology.
“We found that pest abundance was lower and [maize] yield higher in older push-pull fields very consistently across a wide geographic and time range,” says Luttermoser. “We also found some evidence that non-push-pull farms might benefit from being near older push-pull fields.
“Stemborer [moths] and striga [also called witchweed] were both less abundant on control fields paired with older push-pull fields, although the yield was not affected.”
The findings that the abundance of pests in the push-pull system decreased over time suggests that the benefits of using the technology to control pests could last for many years.
The researchers add that ecologically intensified pest management systems such as push-pull systems are more durable than chemical pesticides as pests frequently evolve pesticide resistance but rarely adapt to overcome ecologically intensified systems.
“While there is often some start-up cost and labour involved, reduced pesticide costs year over year can be a substantial economic benefit,” says Zeyaur Khan, a co-author of the study and programme leader of push-pull integrated management technology at the Kenya-headquartered International Centre of Insect Physiology and Ecology.
While the study period was before the fall armyworm invasion in Africa, the authors argue that push-pull remains effective even against fall armyworm as proved by other studies and expect that these results will continue to hold true even in the presence of fall armyworm.
Matilda Ouma, a lecturer in the Department of Agricultural Economics and Agribusiness Management at Jaramogi Oginga Odinga University of Science and Technology in Kenya, says that the study shows that research is evolving and the push-pull technology is getting better.
Ouma, who has adopted the technology on her farm, says that scientists working on the push-pull system have been improving the technology to ensure it adapts to ecological changes.
She agrees with the study that the push-pull system can significantly help improve yields and even soil fertility while being resilient against crop pests.