Revisiting push-pull technology: Below and aboveground mechanisms for ecosystem servicesBella David, Aneth
Push-pull technology is an effective and ecological solution to suppressing major Lepidopteran pests of cereals, in particular stem-borers (Busseola fusca, Chilo partellus), the fall armyworm (Spodoptera frugiperda) and the parasitic weed Striga. The technology exploits plant-insect interactions in intercropping practices to manage the pests, increasing productivity while maintaining ecosystem resilience. In this study, we show that long-term (14 – 18 years) push-pull farming cause shifts in soil microbial communities, increasing the diversity of fungal taxa than bacteria. Further, the shift in the structure of soil microbial populations seems to require time to establish as observed by the weak impact of Desmodium species cultivated for just two years on soil microbial structure. However, even under the short-term cultivation period, individual taxa enrichment associated to the Desmodium were observed. On the other hand, whole soil microorganisms as well as rhizobia appeared to have little impact on the constitutive release of volatile emissions by Desmodium. Whether the plants grew on live or autoclaved soil, Desmodium did not release volatiles implicated in repelling lepidopteran pests, which is in stark contrast to previous reports. Upon herbivory of Desmodium by Spodoptera frugiperda larvae, a marginal increase in volatile emissions was observed. In line with this observation and contrary to expectation, intact Desmodium spp. did not deter oviposition by gravid S. frugiperda. In feeding bioassays, neonate S. frugiperda larvae strongly preferred Desmodium spp. to maize diet, but did not grow well nor did they survive on it. Older larvae were frequently immobilised on the stems, often dying in position after a few days. Deeper investigation showed that stems and leaves of Desmodium were covered with a dense web of straight and hooked silicon-rich trichomes of varying lengths that prevented larval movement, piercing their cuticle in the struggle. In this light, we propose that in a push-pull setting, Desmodium acts as a mechanical barrier and trap crop instead of a volatiles-dependent “push” crop as previously purported. In addition, intercropping practices have been shown to reduce insect pest populations through diverse mechanisms such as barrier effect and resource concentration. Push-pull technology shows that ecological approaches to pest management and increasing productivity can be effective. A clear understanding of the mechanisms of action of such approaches is critical for further improvements as well as translation into other agro-ecological practices.
KeywordsPush-pull technology; Desmodium spp.; soil microbiome; intercropping microbiome; stem-borers; trichomes; ecosystem services
Published inActa Universitatis Agriculturae Sueciae
2022, number: 2022:35
ISBN: 978-91-7760-945-2, eISBN: 978-91-7760-946-9
Publisher: Swedish University of Agricultural Sciences