Research on the Senegalese grasshopper in West Africa
Numerous research projects looking at how land-use practices influence the Senegalese grasshopper (Oedaleus senegalensis) have built on each other over the years, creating a wealth of knowledge on this system and opportunities for alternative management strategies. The Senegalese grasshopper (Oedaleus senegalensis) is among the most severe pests of the Sahel. The population moves seasonally along the inter-tropical convergence zone (ITCZ).[1] This species regularly attacks staple cereal crops which, combined with low soil fertility, reduces farmers’ resiliency and food security. [2]
Foundational research by Touré et. al
Touré et. al showed that O. senegalensis distribution depends on habitat type, rainfall intensity, and year.[3] They found larva density more abundant in fallow fields than millet, bean, or groundnut fields. Crop rotation reduced O. senegalensis density and the grasshopper was overall more abundant in fallow fields. These data suggest that crop type has an important effect on O. senegalensis distribution.
NSF Coupled Natural Human Systems Living with Locusts CNH
This project integrated novel fundamental research from multiple disciplines across four different countries —Australia, China, Senegal, and the US—to improve our ability to manage social-ecological systems. The team investigated physiological, ecological, and nutritional mechanisms responsible for locust outbreaks and migration. This is one of the first projects to apply both highly-controlled lab and field-based techniques to connect physiological mechanisms to agricultural practices and livelihoods. Read about the full project here.
The work specifically in Senegal focused on the Senegalese grasshopper and its agroecosystem. In 2017, Dr. Arianne Cease and Jennifer Learned traveled to the Kaffrine region of Senegal
Background
One of the main conventional ideas in nutritional ecology is that herbivores should face limitations in nitrogen and protein availability. [4] [5][6] However, some locust species show a preference for and exhibit optimal growth in low-nitrogen settings, characterized by plants with low protein content and high carbohydrate levels.[7]
2016 / 2017 field work
Our research was conducted in the Kaffrine region of Senegal. The area is known as the ‘West Central Agricultural Region’, or Peanut Basin (Tappan et al., 2004). The team worked with two villages, Gossas (14°29′44.5′′N 16°04′01.2′′W) and Gnibi (14°26′11.5′′N 15°39′13.6′′W). These villages were chosen because of the prevalence and persistence of O. senegalensis and their similar population size (10,000–13,000 people according to Senegal Census Data, 2013).
The team explored connections among land use, soil, plant nutrients, and locusts. They found that fields and grazing areas with low-nitrogen plants supported higher locust population densities, and therefore increased possibilities for crop damage. [8] [2]
Further research showed that Oedaleus senegalensis prefer carbohydrate-biased food[8] and applying nitrogen fertilizer decreased the survival and reproduction of the species. [9]
Plant N content, especially non-N fixing species, is significantly related to soil inorganic N, which can be linked to farm management decisions. Therefore, despite challenges, it's possible that land use that promotes soil organic matter and nitrogen may suppress outbreaks. This idea is that helped spark the development of the subsequent USDAID project.
Relevant publications
Word ML, Hall SJ, Robinson BE, Manneh B, Beye A, Cease AJ (2019) Soil-targeted interventions could alleviate locust and grasshopper pest pressure in West Africa. Science of The Total Environment 663: 632–643. https://doi.org/10.1016/j.scitotenv.2019.01.313
Le Gall M, Word ML, Thompson N, Beye A, Cease AJ (2020a) Nitrogen fertilizer decreases survival and reproduction of female locusts by increasing plant protein to carbohydrate ratio. Journal of Animal Ecology. https://doi.org/10.1111/1365-2656.13288
Le Gall M, Word ML, Thompson N, Manneh B, Beye A, Cease AJ (2020b) Linking land use and the nutritional ecology of herbivores: A case study with the Senegalese locust. Functional Ecology 34(1):167-181. https://doi.org/10.1111/1365-2435.13466
Le Gall M, Word ML, Beye A, Cease AJ (2021) Physiological status is a stronger predictor of nutrient selection than ambient plant nutrient content for a wild herbivore. Current Research in Insect Science 1: 100004. https://doi.org/10.1016/j.cris.2020.100004
Le Gall M, Beye A, Diallo M, Cease AJ (2022) Generational variation in nutrient regulation for an outbreaking herbivore. Oikos n/a: e09096. https://doi.org/10.1111/oik.09096
USAID Bay Sa Waar Communities for Sustainable Agriculture
2018-2022
This project built on the findings from the work under the NSF CNH grant. It introduced a sustainable methodology for locust management in the Kaffrine Region based on leveraging the biology of the Senegalese grasshopper. The strong findings from 2016 and 2017, showed clear soil-plant-locust interactions, and therefore way that land managers might be able to use this information to design a long-term and community-based preventative management strategy. The first iteration of Bay Sa Waar Communities for Sustainable Agriculture project set up village-based soil amendment and locust monitoring programs to create environments unfavorable to locusts.
Read more details about the project here
Soil amendment intervention
The team worked with 250 farmers from across Senegal, some of them the same farmers who participated in the CNH project. 250 fields were treated with the recommended application of fertilizer to test if increasing plant nitrogen would keep pest populations low and crop yields high. Preliminary results show a decrease in overall damage to fertilized plants.
Early warning system
The team worked with women in five communities to develop a system for monitoring insects with light traps. Communities are along the migratory route of O. senegalensis, expanding the monitored range, and allowing targeted and efficient use of interventions while empowering women to lessen the impacts of locusts. Women learned to monitor using light traps, identify grasshoppers, collect scientific samples, and report data to the government agency responsible for pest management, la Direction de la Protection des Végétaux or DPV.
Learn more about how to build and use a light trap here
2023-2025
Aim 1. Model with web interface: extension of the agent based model and co-development of a web-based user interface with end user stakeholders.
Aim 2. Sustainable Soil Amendments: implementation of sustainable pathways for improving soil fertility and suppressing pest populations, including composting and woody vegetation, with an emphasis on women farmers.
Aim 3. Integration from local to NPPO levels: focus groups that will identify barriers and leverage points for implementing the first and second components, as well as integrating alternative pest management tools into National Plant Protection Organization (NPPO) practice.
Aim 4. Expanding global partners and resources: through the Global Locust Initiative (GLI) Network and HopperWiki.
Impact of compost on grasshopper density
In 2023 the team completed training sessions on composting techniques. Subsidies for purchase of composting equipment have been sent via electronic transfer and seeds have been distributed to each beneficiary.
Focus groups to discuss the composting project and perceptions
Focus groups were conducted between April 29th and May 2nd, 2023, the team conducted focus groups with the four communities involved in the project. These focus groups aimed to support discussions within the community regarding the following issues: 1) the risk represented by locusts and grasshoppers for their well-being 2) their use of multiple fertilization techniques as well as their strengths and weaknesses, in particular composting and 3) the potential leverage points to promote the adoption of composting practices. The focus groups were conducted the villages of Gniby (n = 22 participants), Gossas (n = 21), Mbalmy (n = 35) and Toubatoule (n = 21), thus reaching a total of 99 participants (55 men and 44 women), more than the 80 originally planned.
References
- ↑ Kabeh JD (2008) Dry Season Egg Pod Survey and Eclosion in Oedaleus senegalensis, Krauss (Orthoptera: Acrididae) in the Sudan Savanna of Nigeria. International Journal of Agriculture and Biology. 9: 881-884
- ↑ 2.0 2.1 Word ML, Hall SJ, Robinson BE, Manneh B, Beye A, Cease AJ (2019) Soil-targeted interventions could alleviate locust and grasshopper pest pressure in West Africa. Science of The Total Environment 663: 632–643. https://doi.org/10.1016/j.scitotenv.2019.01.313
- ↑ Touré M, Ndiaye M, Dongue A (2013a) Effect of cultural techniques: Rotation and fallow on the distribution of Oedaleus senegalensis (Krauss, 1877) (Orthoptera:Acrididae) in Senegal. African Journal of Agriculture Research. 8: 5634–5638. https://doi.org/10.5897/AJAR11.2353.
- ↑ Andrewartha HG (1954) The distribution and abundance of animals. University of Chicago Press, Chicago. 782 pp.
- ↑ Mattson WJ (1980) Herbivory in relation to plant nitrogen content. Annual Review of Ecology and Systematics 11: 119–161. https://doi.org/10.1146/annurev.es.11.110180.00
- ↑ White TCR (1993) The inadequate environment: nitrogen and the abundance of animals. Springer-Verlag Berlin.
- ↑ Le Gall M, Overson R, Cease A (2019) A Global Review on Locusts (Orthoptera: Acrididae) and Their Interactions With Livestock Grazing Practices. Frontiers in Ecology and Evolution 7: 263. https://doi.org/10.3389/fevo.2019.00263
- ↑ 8.0 8.1 Le Gall M, Word ML, Thompson N, Manneh B, Beye A, Cease AJ (2020b) Linking land use and the nutritional ecology of herbivores: a case study with the Senegalese locust. Functional Ecology. https://doi.org/10.1111/1365-2435.13466
- ↑ Le Gall M, Word ML, Thompson N, Beye A, Cease AJ (2020a) Nitrogen fertilizer decreases survival and reproduction of female locusts by increasing plant protein to carbohydrate ratio. Journal of Animal Ecology: 1–8. https://doi.org/10.1111/1365-2656.13288