Competitive Plant-Mediated and Intraguild Predation Interactions of the Invasive Spodoptera frugiperda and Resident Stemborers Busseola fusca and Chilo partellus in Maize Cropping Systems in Kenya

Abstract

Following its recent invasion of African countries, fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), now co-exists with resident stemborers such as Busseola fusca (Lepidoptera: Noctuidae) and Chilo partellus (Lepidoptera: Crambidae) causing severe damage to maize crops. Due to niche overlap, interspecific interactions occur among the three species, but the mechanisms and degree remain unclear. In this study, we assessed plant-mediated intraspecific and interspecific interactions, predation in laboratory and semi-field settings, and larval field occurrence of S. frugiperda and the two stemborer species. Larval feeding assays to evaluate competitive plant-mediated interactions demonstrated that initial S. frugiperda feeding negatively affected subsequent stemborer larval feeding and survival, suggesting induction of herbivore-induced mechanisms by S. frugiperda, which deters establishment and survival of competing species. Predation assays showed that, at different developmental larval stages, second–sixth instars of S. frugiperda preyed on larvae of both B. fusca and C. partellus. Predation rates of S. frugiperda on stemborers was significantly higher than cannibalism of S. frugiperda and its conspecifics (p < 0.001). Cannibalism of S. frugiperda in the presence of stemborers was significantly lower than in the presence of conspecifics (p = 0.04). Field surveys showed a significantly higher number of S. frugiperda larvae than stemborers across three altitudinally different agroecological zones (p < 0.001). In conclusion, this study showed that the invasive S. frugiperda exhibited a clear competitive advantage over resident stemborers within maize cropping systems in Kenya. Our findings reveal some of the possible mechanisms employed by S. frugiperda to outcompete resident stemborers and provide crucial information for developing pest management strategies for these lepidopteran pests.

Interspecific Competition between Invasive Spodoptera frugiperda and Indigenous Helicoverpa armigera in Maize Fields of China

“…Song et al (2021) observed that the early development stages of FAW could repel S. litura larvae from maize whorls [28]. In Uganda, resident stemborers B. fusca and Chilo partellus were possibly displaced from maize to sorghum to evade competition from invasive FAW larvae [55,56]. The prevalence of CBW in other host plants requires more extensive and longterm investigations in the future, as acquiring this information is important in developing pest monitoring and management strategies.…”

The Structure of Rice Stemborer Assemblages: A Review of Species’ Distributions, Host Ranges, and Interspecific Interactions

“…It may also allow weaker competitors to maintain populations in the rice landscape during periods when some superior competitor is most abundant [235]. For example, the recent invasions of Fall Armyworm, Spodoptera frugiperda (J. E. Smith) in Africa and Asia, have been associated with a declining abundance of native stemborers in maize [236][237][238][239][240][241], even though S. frugiperda is not a stemborer, but a leaf chewer. This is partly due to predation of neonate stemborers before they enter the stem by S. frugiperda at high post-introduction densities-as shown in laboratory experiments [238,240,241].…”

Effectiveness of Neem Oil and Jatropha Oil in Controlling Spodoptera frugiperda (J.E Smith) on Maize in the Republic of Chad

“…The number of cobs attacked and the overall cobs damage index were determined and recorded per elementary plot. It has indeed been shown from recent studies that the invasive S. frugiperda exhibited a clear competitive advantage over other resident stemborers within maize cropping systems, thereby quickly excluding the latter through several mechanisms including intraguild predation (Mutua et al, 2022). Therefore, where S. frugiperda is present, damages can almost exclusively be attributed to hat invasive pest…”