article · Chemical and Biological Technologies in Agriculture
Fall armyworm is an invasive pest that causes maize yield losses of 20 to 50 percent in Africa. This study examined how odours from six companion crops, including beans, groundnut, sweet potato, greenleaf desmodium, silverleaf desmodium, and cassava, affect the behaviour of the pest and its larval parasitoid, Cotesia icipe. In multiple-choice tests, the presence of companion plants, except cassava, significantly reduced fall armyworm egg laying on maize. Wind tunnel bioassays confirmed these altered behavioural responses, while the parasitoid was attracted to volatiles emitted by the companion crops alone or mixed with maize. Chemical analysis identified several behaviour-modifying volatile compounds, including camphor and methyl salicylate. These findings show that diversifying maize fields with companion crops can deter fall armyworm while recruiting natural biological control agents, providing an ecologically sustainable management approach.
Fall armyworm poses a severe threat to food security across Africa, causing substantial yield losses in staple cereals. Demonstrating that companion crops naturally deter the pest and attract its parasitic enemies offers an accessible, environmentally friendly management approach. This supports integrated pest management strategies that can protect crops naturally while reducing reliance on synthetic chemical insecticides.
This is early-stage laboratory and bioassay research that could inform the design of diversified cropping systems by agricultural practitioners and extension services. In addition, the identified behaviour-modifying volatile compounds could provide chemical targets for biopesticide or semiochemical developers formulating pest repellents and parasitoid attractants. Real-world commercial or agronomic application will require further testing in open-field conditions to validate effectiveness.
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Abstract Background The fall armyworm (FAW), Spodoptera frugiperda , is a devastating invasive pest and a threat to food security in Africa, with yield losses of 20–50%. Recent studies highlighted the importance of cereal crops such as maize and sorghum as the most preferred host plants for FAW oviposition. In the current work, we investigated the olfactory responses of FAW and its key larval endoparasitoid Cotesia icipe to odours from the preferred host (maize) in the presence of six potential companion crops including beans, groundnut, sweet potato, greenleaf- and silverleaf desmodium, and cassava. We hypothesized that odours released by companion crops in maize-based intercropping systems would alter host preferences of FAW for oviposition and its parasitoid responses. Results In dual choice oviposition bioassays, FAW laid significantly more eggs on maize than on the other plants. However, in the multiple-choice bioassays, significantly fewer eggs were laid on maize when companion plants were present except cassava. While wind tunnel bioassays confirmed the differential behavioural responses of FAW, we found that its larval endoparasitoid C. icipe was attracted to volatiles from the companion plants tested individually and/or when they were combined with maize. Coupled gas chromatography–mass spectrometry (GC–MS) analysis detected several potential behaviour-modifying compounds including ( Z )-3-hexenyl acetate, ( E )-β-ocimene, ( E )-4,8-dimethyl-1,3,7-nonatriene, ( E )-β-caryophyllene, camphor, methyl salicylate and ( E, E )-4,8,12-trimethyl-1,3,7,11-tridecatetraene. Conclusions Our findings provide evidence supporting diversified maize cropping system could reduce FAW damage by repelling the pest while simultaneously recruiting its natural enemies. Hence, diversifying cereal cropping system with companion crops could serve as an ecologically sustainable FAW management strategy. Graphical Abstract
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DOI: 10.1186/s40538-023-00415-6
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