Population dynamics of Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) and associated arthropod natural enemies in Honduran subsistence maize

Abstract

We investigated relationships between the population dynamics of the pest insect, the fall armyworm Spodoptera frugiperda (Smith) and associated natural enemies within small-scale maize fields in the Honduran highlands. In general, pest infestation levels remained below regionally defined economic thresholds. A broad complex of arthropod predators, parasitoids and entomopathogens was recorded from field plots. Low levels (1–11%) of parasitism of Spodoptera frugiperda were recorded, with the braconid Aleiodes laphygmae (Viereck) and the ichneumonid Campoletis sonorensis (Cameron) the most commonly observed parasitoids. Incidence of entomopathogens and parasitic nematodes was low, affecting only 3.8% of collected fall armyworm larvae. The most abundant predator was the earwig Doru taeniatum (Dorhn), which reached maximum densities of 2.3 individuals per plant. Frequently observed predators belonged to the order Aranea and insect families Formicidae, Carabidae and Pentatomidae. The ant community was dominated by the fire ant Solenopsis geminata (F.). Natural enemy abundance and diversity differed considerably between fields, as did their associations with fall armyworm infestation. High abundance of spiders during early maize developmental stages was associated with lowered pest levels. High abundance of ground beetles and earwigs was associated with lowered pest population levels throughout the maize vegetative cycle. Time-lagged relationships were found between pest population dynamics and the abundance of vespid wasps and ants. Spodoptera frugiperda infestation levels were lower at higher altitudes. When correcting for altitudinal effects, many associations between predator abundance and fall armyworm dynamics remained valid. Our study shows that the interaction between altitude, the natural enemy community and fall armyworm population dynamics in maize fields needs to be taken into consideration for the development of IPM in this crop. We suggest that conservation biological control programs can take advantage of the impact of predators and provide management recommendations tailored to the region's subsistence farming sector.